Note: Descriptions are shown in the official language in which they were submitted.
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CATHETER APPARATUS HAVING AN IMPROVED SHAPE-MEMORY
ALLOY CUFF AND INFLATABLE ON-DEMAND BALLOON FOR
CREATING A BYPASS GRAFT IN-VIVO
CROSS REFERENCE
The present application is a Continuation-In-Part of United States Patent
i0 Application Serial No. 702,068 filed August 23, 1996, now allowed; which
was a
Continuation-In-Part of United States Patent Application Serial No. 6b4,165
filed
June 14, 1996, now U.S. Patent No. 5,676,670 issued October 14, 1997.
FIELD OF THE INVENTION
The present invention is concerned generally with minimally invasive
vascular bypass surgery; and is directed to a catheterization methodology for
creating a vascular bypass between an unobstructed artery or vein and an
obstructed artery ar vein in-vivo.
BACKGROUND OF THE INVEN'~ION
. Coronary artery disease is the single leading cause of human mortality and
is annually responsible for over 900,000 deaths in the United States alone.
Additionally, over 3 million Americans suffer chest pain (angina pectoris)
because
of it. Typically, the coronary artery becomes narrowed over time by the build
up
of fat, cholesterol and blood clots. This narrowing of the artery is called
arteriosclerosis; and this condition slows the blood flow to the heart muscle
(myocardium) and leads to angina pectoris due to a lack of nutrients and
adequate
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oxygen supply. Sometimes it can also completely stop the blood flow to the
heart
causing permanent damage to the myocardium, the sa-called "heart attack. "
The conventional treatment procedures for coronary artery disease vary
with the severity of the condition. If the coronary artery disease is mild, it
is first
treated with diet and exercise. If this first course of treatment is not
effective, then
the condition is treated with medications. However, even with medications, if
chest pain persists (which is usually secondary to development of serious
coronary
artery disease), the condition is often treated with invasive procedures to
improve
blood flow to the heart: Currently, there are several types of invasive
procedures:
(1) Catheterization techniques by which cardiologists use balloon catheters;
atherectamy devices ar stents to reopen up the blockage of coronary arteries;
or (2)
Surgical bypass techniques by which surgeons surgically place a graft obtained
from a section of artery or vein removed from other parts of the body to
bypass
the blockage.
i5 Conventionally, before the invasive procedures are begun, coronary artery
angiography is usually performed to evaluate the extent and severity of the
coronary artery blockages. Cardiologists or radiologists thread a thin
catheter
through an artery in the leg or arm to engage the coronary arteries. X-ray dye
(contrast medium) is then injected into the coronary artery through a portal
in the
catheter, which makes the coronary arteries visible under X-ray, so that the
position and size of the blockages in the coronary arteries can be identified.
Each
year in U.S.A., more than one million individuals with angina pectoris or
heart
attack undergo coronary angiographies for evaluation of such coronary artery
blockages. Once the blocked arteries are identified, the physician and
surgeons
then decide upon the best method to treat them.
One of the medically accepted ways to deal with coronary arterial blockage
is percutaneous transluminal coronary angiaplasty (PTCA). In this procedure,
cardiologists thread a balloon catheter into the blocked coronary artery and
stretch
it by inflating the balloon against the arterial plaques causing vascular
blockage.
The PTCA procedure immediately improves blood flow in the coronary arteries,
relieves angina pectoris, and prevents heart attacks. Approximately 400,000
patients undergo PTCA each year in the U.S. However, when the arterial
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blockages are severe or widespread, the angioplasty procedure may fail or
cannot
be performed. In these instances, coronary artery bypass graft (CABG) surgery
is
then typically performed. In such bypass surgery, surgeons typically harvest
healthy blood vessels from another part of the body and use them as vascular
grafts
to bypass the blocked coronary arteries. Each vascular graft is surgically
attached
with one of its ends joined to the aorta and the other end joined to the
coronary
artery. Approximately 500,000 CABG operations are currently performed in the
U.S. each year to relieve symptoms and improve survival from heart attack.
It is useful here to understand in depth what a coronary arterial bypass
entails and demands both for the patient and for the cardiac surgeon. In a
standard
coronary bypass operation, the surgeon must first make a foot-long incision in
the
chest and split the breast bone of the patient. The operation requires the use
of a
heart-lung machine that keeps the blood circulating while the heart is being
stopped
and the surgeon places and attaches the bypass grafts. To stop the heart, the
coronary arteries also have to be perfused with a cold potassium solution
(cardioplegia). In addition, the body temperature of the patient is lowered by
cooling the blood as it circulates through the heart-lung machine in order to
preserve the heart and other vital organs. Then, as the heart is stopped and a
heart-lung machine pumps oxygenated blood through the patient's body, the
surgeon makes a tiny opening into the front wall of the target coronary artery
with
a very fine knife (arteriotomy); takes a previously excised saphenous vein (a
vein
from a leg) or an internal mammary artery (an artery from the chest); and sews
the
previously excised blood vessel to the coronary artery.
The most common blood vessel harvested for use as a graft is the greater
25, (long) saphenous vein, which is a long straight vein running from just
inside the
ankle bone to the groin. The greater saphenous vein provides a bypass conduit
of
the most desired size, shape, and length for use with coronary arteries. The
other
blood vessel frequently used as a bypass graft is the left or right internal
mammary
artery, which comes off the subclavian artery and runs alongside the
undersurface
of the breastbone (sternum). Typically, the internal mammary artery remains
attached to the subclavian artery proximally (its upper part) but is freed up
distally
(its lower part); and it is then anastomosed to the coronary artery. However,
the
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saphenous vein graft should be sewn not only to coronary artery but also to
the
aorta, since the excised vein is detached at both ends. Then, to create the
anastomosis at the aorta, the ascending thoracic aorta is first partially
clamped
using a curved vascular clamp to occlude the proper segment of the ascending
aorta; and a hole is then created through the front wall of the aorta to
anchor the
vein graft with sutures. The graft bypasses the blockage in the coronary
artery and
restores adequate blood flow to the heart. After completion of the grafting,
the
patient is taken off of the heart-lung machine and the patient's heart starts
beating
again. Most of the patients can leave the hospital in about 6 days after the
CABG
procedure.
It will be noted that coronary artery bypass surgery is considered a more
definitive method for treating coronary arterial disease because all kinds of
obstructions cannot be treated by angioplasty; and because a recurrence of
blockages in the coronary arteries even after angioplasty is not unusual. Also
coronary artery bypass surgery usually provides for a longer potency of the
grafts
and the bypassed coronary arteries in comparison with the results of PTCA
procedure. However, coronary artery bypass surgery is a far more complicated
procedure, having need of a heart-lung machine and a stoppage of the heart.
Also,
it is clearly the more invasive procedure and is more expensive to perform
than
PTCA. Therefore, cardiac surgeons have recently developed an alternative to
the
standard bypass surgery, namely "minimally invasive bypass operation (MIBO) in
order to reduce the risks and the cost associated with CABG surgery. Also, the
MIBO is performed without use of a heart-lung machine or the stopping of the
heart.
There are several ways that minimally invasive coronary bypass surgeries
are being done today. Some versions are modeled after the video-assisted,
fiber-
optic techniques developed previously for galibladder and other general
surgeries.
Other techniques have modified decades-old methods to sew arterial grafts onto
beating hearts without using heart-lung machines. In the new and most popular
version of the minimally invasive coronary bypass operation, surgeons use a
thoracoscope, a fiber-optic device that is similar to a Iaparoscope.
Initially, a
three-inch incision is made to the left of the breast bone through which the
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surgeons operate. Three additional one-inch incisions then are made to insert
a
video camera, knife, surgical stapler; and other instruments. In the first
stage of
the operation, surgeons prepare the internal mammary artery, which courses
vertically behind the rib cage, while watching on a video monitor. The
internal
mammary artery is freed up distally and is then sewn to the left anterior
descending coronary artery. The internal mammary artery thus supplies blood to
the coronary artery in place of blocked circulation of the heart. The wall of
the
chest formerly served by the mammary artery picks up blood from elsewhere via
collateral blood circulations.
As a bypass graft, the left internal mammary artery {LIMA} offers a
number of advantages to the saphenous vein graft including higher potency
rate;
and anatomically, histologically and geometrically provides a more comparable
graft than the saphenous vein graft. LIMA is particularly useful as a graft to
the
coronary arteries such as the left anterior descending, diagonal branches, and
ramus intermedius arteries (which are located on the surface of the heart
relatively
close to the left internal mammary artery). However, there are several
disadvantages associated with a CABG operation with a left internal mammary
artery graft, which are as follows: (1} technically, this artery is more
tedious to
take down; (2) sometimes the left internal mammary artery is inadequate in
size
and length; (3) the operation is suitable only for the five percent of
candidates for
coronary artery bypass because only a single left internal mammary artery is
available as a graft; (4) anatomically, the operation is limited mainly to the
left
anterior descending coronary artery because of its location ad length; and (5)
the
majority of patients need more than single vessel bypass surgery.
In comparison, coronary arteries as small as 1 mm in diameter can be
revascularized by vein grafting; and the saphenous vein is longer, larger, and
more
accessible than the left internal mammary artery. Equally important, although
the
greater or lesser saphenous veins of the leg are preferred, the cephalic or
basilic
veins in the arm are available as alternatives when the leg veins in the
patient are
unavailable or are unsuitable. For these reasons, the vein graft has today
become
the standard conduit for myocardial revascularization.
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There remains, however, a long-standing and continuing need for a bypass
technique which would allow surgeons to perform multiple bypass procedures
using
vein grafts as vascular shunts in a minimally invasive way; and, in
particular, the
need remains for a simpler method to place more than one vein graft proximally
to
S the aorta and distally to the coronary artery without using a heart-lung
machine and
without stopping the heart. If such a technique were to be created, it would
be
recognized as a major advance in bypass surgery and be of substantial benefit
and
advantage for the patient suffering from coronary artery disease.
SUMMARY OF THE INVENTION
The present invention has multiple aspects. A first aspect provides a
catheter apparatus for creating a bypass on-demand between an unobstructed
blood
vessel and an obstructed blood vessel in-vivo using a graft segment as a
conduit,
said bypass catheter apparatus comprising:
a catheter suitable for introduction into and extension through the body in-
vivo to a chosen site wherein an unobstructed blood vessel is in anatomic
proximity
to an obstruction Iying within another blood vessel, said catheter being
comprised
of a hollow tube of fixed axial length having a proximal end, a distal end,
and at
least one internal lumen of predetermined diameter;
an obturator for on-demand introduction and passage through said catheter
to a chosen site on the unobstructed blood vessel in-vivo, said obturator
comprising
(a) a puncturing headpiece for puncture of and entry into the
lumen of an unobstructed blood vessel,
(b) a perforating end tip on said puncturing headpiece to
facilitate the perforation of a blood vessel wall at the chosen site in-vivo,
(c) an elongated shaft of fixed axial length integrated with said
puncturing headpiece, said elongated shaft being configured for the carrying
and
transport of a graft segment within said internal lumen of said catheter to
the
chosen site on the unobstructed blood vessel in-vivo; and
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a thermoelastic deformabie cuff comprised of a prepared shape-memory
alloy in a chosen extant configuration for positioning over said elongated
shaft
adjacent to said puncturing headpiece of said obturator together with a graft
segment, said thermoelastic deformable cuff having a discrete medial portion
and
two discrete end portions
(i) wherein, prior to the perforation of the unobstructed blood
vessel in-vivo by said puncturing headpiece of said obturator, said medial
portion
of said cuff has been engaged and joined to one end of the graft segment then
carried by said elongated shaft of said obturator thereby forming an engaged
medial cuff portion and two discrete non-engaged cuff end portions,
(ii} and wherein, after the perforation of the unobstructed blood
vessel in-vivo by said puncturing headpiece of said obturator, one of said non-
engaged cuff end portions is extended into the lumen of the unobstructed blood
vessel, and becomes thermoelastically deformed in-situ within the lumen of the
unobstructed blood vessel into a prepared memory-shaped end configuration, and
is
disposed in the prepared memory-shaped end configuration onto an interior
surface
of the unobstructed blood vessel,
{iii) and wherein, after the perforation of the unobstructed blood
vessel in-vivo by said puncturing headpiece of said obturator, the other of
said non-
engaged cuff end portions is positioned adjacent an exterior surface of the
unobstructed blood vessel, and becomes thermoelastically deformed in-situ
adjacent
the exterior surface of the unobstructed blood vessel into another prepared
memory-shaped end configuration, and is disposed in the other prepared memory-
shaped end configuration onto an exterior surface of the unobstructed blood
vessel,
25, (iv) and whereby the end of the graft segment engaged by the medial
portion of the cuff becomes secured to and placed in blood flow communication
with the unobstructed blood vessel and serves as conduit means for bypassing
an
obstruction and restoring blood flow from the unobstructed blood vessel to an
obstructed blood vessel.
A second aspect of the present invention provides a catheter apparatus for
creating a bypass on-demand between an unobstructed blood vessel and an
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obstructed blood vessel in-viva using a graft segment as a conduit, said
bypass
catheter apparatus comprising:
a catheter suitable for introduction into and extension through the body in-
vivo to a chosen site wherein an unobstructed blood vessel is in anatomic
proximity
S to an obstruction lying within another blood vessel, said catheter being
comprised
of a hollow tube of fixed axial length having a proximal end, a distal end,
and at
least one internal lumen of predetermined diameter;
an obturator for on-demand introduction and passage through said catheter
to a chosen site on the unobstructed blood vessel in-vivo, said obturator
comprising
1~ {a) a puncturing headpiece far puncture of and entry into the
lumen of an unobstructed blood vessel,
(b) a perforating end tip on said puncturing headpiece to
facilitate the perforation of a blood vessel wall at the chosen site in-vivo,
{c) an elongated shaft of fixed axial length integrated with said
1S puncturing headpiece, said elongated shaft being configured for the
carrying and
transport of a graft segment within said internal lumen of said catheter to
the
chosen 'site on the unobstructed blood vessel in-vivo;
an inflatable and deflatable on-demand balloon of prechosen configuration
disposed adjacent to said puncturing headpiece on said elongated shaft of said
20 obturator, the girth of said balloon in the deflated state being less than
the internal
diameter of the graft segment to be used as a conduit; and
a thermoelastic deformable cuff comprised of a prepared shape-memory
alloy in an chosen extant configuration for positioning over said elongated
shaft
adjacent to said puncturing headpiece of said obturator together with a graft
2S , segment to be used as a conduit, said thermoelastic deformable cuff
having a
discrete medial portion and two discrete end portions
(i) wherein, prior to the perforation of the unobstructed blood
vessel in-vivo by said puncturing headpiece of said obturator, said discrete
medial
portion of said cuff has been engaged and joined to one end of the graft
segment
30 then carried by said elongated shaft of said obturator thereby forming an
engaged
medial cuff portion and two discrete non-engaged cuff end portions,
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(ii) and wherein, after the-perforation of the unobstructed blood
vessel ,in-vivo by said puncturing headpiece of said obturator, one of said
non-
engaged cuff end portions is extended into the lumen of the unobstructed blood
vessel, and becomes thermoelastically deformed in-situ within the lumen of the
unobstructed blood vessel into a prepared memory-shaped end configuration, and
is
disposed in the prepared memory-shaped end configuration onto an interior
surface
of the unobstructed blood vessel,
(iii) and wherein, after the perforation of the unobstructed blood
vessel in-vivo by said puncturing headpiece of said obturator, the other of
said non-
IO engaged cuff end portions is positioned adjacent an exterior surface of the
unobstructed blood vessel, and becomes thermoelastically deformed in-situ
adjacent
the exterior surface of the unobstructed blood vessel into another prepared
memory-shaped end configuration, and is disposed in the other prepared memory-
shaped end configuration onto an exterior surface of the unobstructed blood
vessel,
(iv) and whereby the end of the graft segment engaged by the
medial portion of the cuff becomes secured to and placed in blood flow
communication with the unobstructed blood vessel and serves as conduit means
for
bypassing an obstruction and restoring blood flow from the unobstructed blood
vessel to an obstructed blood vessel.
BRIEF DESCRIPTION OF THE FIGURES
The present invention may be more easily and completely understood when
, taken in conjunction with the accompanying drawing, in which:
Fig. 1 is an overhead view of a conventionally known first catheter;
Fig. 2 is an overhead view of a conventionally known second catheter;
Figs. 3A and 3B are perspective and cross-sectional views of a single wall
catheter tube of normal thickness;
Figs. 4A and 4B are perspective and cross-sectional views of a single wall
catheter tube of reduced thickness;
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Figs. SA and SB are perspective and cross-sectional views of a multiple-
wall catheter tube of normal thickness;
Figs. 6A and 6B are perspective and cross-sectional views of a multiple-
wall catheter tube of reduced thickness;
Figs. 7A-7D are cross-sectional views of four different constructions of
dual-lumen catheters;
Fig. 8 is an illustration of a conventionally known introducer catheter;
Fig. 9 is a perspective view of a preferred first obturator;
Fig. 10 is a frontal view of the first obturator of Fig: 9;
Fig. 1 I is a side view of the puncturing headpiece of the first obturator
shown in Fig. 9;
Fig. 12 is a side view of the puncturing headpiece of Fig. 1 I when in a
contracted state;
Fig. 13 is a side view of the puncturing headpiece of Fig. I1 when in an
expanded state;
Fig. 14 is an exposed view of a mechanical assembly used for expanding
and contracting a puncturing headpiece on-demand in an obturator;
Fig. 15 is an exposed view of a hydraulic assembly for expanding and
contracting a puncturing headpiece on-demand in an obturator;
Fig. 16 is a perspective view of a second obturator;
Fig. 17 is a frontal view of the second obturator of Fig. 16;
Fig. 18 is a perspective view of a third obturator;
Fig. I9 is a frontal view of the third abturator of Fig. 18;
Fig. 20 is a side view of an alternative fourth puncturing headpiece of an
25, obturator;
Fig. 21 is a side view of an alternative fifth puncturing headpiece of an
obturator;
Figs. 22A and 22B are side and top views of an alternative sixth obturator;
Figs. 23A and 23B are overhead and side views of a small-box pattern
meshwork;
Figs. 24A and 24B are overhead and side views of a large-box pattern
meshwork;
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Figs. 25A and 25B are overhead and side views of a nets patterns
meshwork;
Figs. 26A and 26B are overhead and side views of a brick pattern
meshwork;
Figs. 27A and 27B are overhead and side views of a spiral pattern
meshwork;
Figs. 28A and 28B are overhead and side views of a honeycomb pattern
meshwork;
Fig. 29 is a view of a circular and smooth cuff end perimeter outline;
Figs. 30A and 30B are views of large and small petaloid cuff end perimeter
outlines;
Fig. 31 is a view of a bare wire endpoint perimeter for a cuff end;
Figs. 32A-32C are views of a preformed first cuff embodiment in the extant
and prepared memory-shaped configurations;
Figs. 33A-33C are views of a preformed second cuff embodiment in the
extant and prepared memory-shaped configurations;
Figs. 34A-34C are views of an alternative cuff end perimeter outline for the
embodiment of Fig. 33;
Figs. 35A-35C are views of a third preformed cuff embodiment in the
extant and prepared memory-shaped configuration;
Figs. 36A-36D are views of an alternative fourth cuff embodiment in the
extant and prepared memory-shaped conf gurations;
Figs. 37A-378 are views of an alternative fifth cuff embodiment in the
extant and prepared memory-shaped configurations;
, Figs. 38A-38C are views of an alternative sixth cuff embodiment in the
extant and prepared memory-shaped configurations;
Figs. 39A and 39B are cross sectional and side views of an inflatable and
deflatable on-demand balloon;
Figs. 40A and 40B are overhead and side views of an inflatable and
deflatable balloon of Fig. 39 properly positioned on an obturator;
Figs. 41A and 41B are overhead and side views of the positioned balloon of
Fig. 40 in the inflated state;
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Fig. 42 is a perspective view of a previously excised vascular graft segment
positioned over the balloon of Fig. 40 on the elongated shaft of the
obturator;
Fig. 43 is a perspective view of the preferred fast cuff embodiment of Fig.
23A in combination with the previously excised vascular segment as shown by
Fig.
42;
Fig. 44 is a partially exposed view of the improved introduces system as a
whole;
Figs: 45A-45F are illustrations of the modified Seldinger technique
conventionally used for percutaneous caiherterization;
Fig. 46 is a partially exposed view of the improved introduces system in the
correct position at the exterior wall of an unobstructed blood vessel in-vivo;
Fig. 47 is a partially exposed view of the improved introduces system
penetrating the vascular wall of the unobstructed blood vessel in-vivo;
Fig. 48 is a partially exposed view of the improved introduces system
I5 within the internal lumen of the unobstructed blood vessel in=vivo;
Fig. 49 is a partially exposed view of the engaged cuff beginning partial
thermal deformation in-situ while being extended into the internal lumen of
the
unobstructed blood vessel in-vivo;
Fig. 50 is a partially exposed view of the engaged cuff continuing partial
thermal deformation solely within the internal lumen of the unobstructed blood
vessel in-vivo;
Fig. 51 is a partially exposed view of the engaged cuff after subsequent
partial thermal deformation in-situ adjacent the exterior wall surface of the
unobstructed blood vessel in-vivo;
Fig. 52 is a partially exposed view of the completely deformed cuff and
vascular segment secured fluid-tight to and in blood flow communication with
the
internal lumen of the unobstructed blood vessel in-vivo;
Fig. 53 is a partially exposed view of the bypass conduit grafted
additionally secured to the unobstructed blood vessel in-vivo by biocompatible
adhesives; and
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Fig. 54 is a partially exposed view of the other open end of the bypass
conduit anastomosed in the conventionally known manner to another obstructed
blood vessel.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a catheter apparatus and catherization technique for
creating a single bypass or multiple bypasses on-demand between an
unobstructed
blood vessel such as the aorta and an obstructed blood vessel such as an
obstructed
coronary artery in-vivo. The present invention utilizes either a synthetic
prosthetic
channel section or a previously excised vascular segment as a grafted conduit;
and
employs a catheterized introduces system having an improved shape-memory alloy
cuff, and an inflatable on-demand balloon in combination with the graft
segment to
create single or multiple shunts which overcome the obstruction in-vivo. The
grafted conduit will then deliver blood from a primary blood vessel, around
the
obstruction, into a secondary artery or vein in order to increase and/or
maintain
proper blood circulation in the living body. A number of substantial
advantages
and major benefits are therefore provided by the present invention, same of
which
include the following:
1. The present invention provides the means for surgeons to perform
multiple bypass grafts in a minimally invasive manner. The methodology permits
the surgeon to utilize either synthetic prosthetic channel sections or
previously
excised veins or arteries as bypass conduits; and allows the surgeon to place
each
25, of the bypass conduits from a primary unobstructed artery (such as the
aorta) to a
secondary obstructed artery (such as the obstructed coronary artery) without
using
a heart-lung machine and without need for stopping the heart during surgery.
2. The present invention simplifies the complexity of conventional
bypass surgery and makes the surgery less invasive. Moreover, the technique
provides the ability to create multiple bypass conduits using a
catheterization
procedure which not only shortens the conventional operation time for surgery
but
also makes the bypass surgery safer and more cost effective.
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3. The present invention is suitable for creating a single bypass graft or
multiple bypass grafts in any medical situation, condition, or pathology in
which
there is a need for increased blood flow to a specific blood vessel or
vascular area
or body region. The cause or source of the medical problem may be an
S obstruction in a blood vessel; or a narrowing or thickening of a blood
vessel wall;
or a diminution or narrowing of a vascular section in a particular blood
vessel.
Each of these medical conditions has its particular cause, origin, or source;
and
each of these pathologies, though different in origin, causes a similar effect
overall
-- a loss of blood flow and blood pressure within the blood vessel.
Accordingly,
I0 the present invention is deemed useful and desirable to overcome any of
these
particular medical conditions and instances where there is a demonstrated need
for
increased blood pressure and blood volume flow within a particular blood
vessel in
the body.
4. The present apparatus and methodology can be employed to create a
15 bypass conduit between any two blood vessels. In many instances, the bypass
conduit wil be made between a primary unobstructed artery and a secondary
obstructed artery, a typical example being a bypass between the ascending
aorta
and an obstructed coronary artery. I~iowever, a bypass shunt may also be
created
between any two veins (such as between the portal vein and the inferior vena
20 cava); or between an artery and a vein (such as between the superior vena
cava
and a pulmonary artery). Equally important, although the primary focus of the
present invention is the thoracic cavity and the recognized need for bypass
conduits
among the blood vessels found therein, the present apparatus and methodology
may
be employed anywhere in the human body where there is a need for increased
25, vascularization or revascularization of the local region. The sole
limitation,
therefore, is a means of access for the catheter apparatus, the introduces
system,
and the methodology to be performed by the skilled surgeon and interventional
radiologist.
In order to provide a complete and comprehensive understanding of the
30 present invention, the detailed description is given as a series of
individual sections
presented seriatim. These will include the following: the component parts of
the
catheter apparatus; the synthetic prosthetic channel section or excised blood
vessel
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segment to be used as a bypass conduit; the introducer system utilizing the
catheter
apparatus and bypass conduit in combination; general techniques of catheter
routing
and surgical introduction; the methodology and individual manipulations for
creating a bypass graft; and an illustrative summary of the preferred surgical
procedures using the catheter apparatus, introducer system, and methodology.
Each of these will be described and characterized individually.
I. T6e Component Parts Of T6e Catheter Apparatus
Three essential component parts comprise the catheter apparatus needed to
create a bypass in-vivo. These are: a catheter; an obturator having a
puncturing
headpiece; and an improved deformable thermoelastic cuff formed of a prepared
shape-memory alloy far engaging and securing a synthetic prosthesis or a
previously excised vascular segment as a bypass conduit to an unobstructed
major
blood vessel {such as the aorta). Each of these component parts will be
described
in detail individually.
A. The Catheter
The in-vivo bypass catheterization method comprising the present invention
requires that a guiding or introducer catheter be employed as a essential part
of the
apparatus. This controlling or guiding flexible catheter has at least one
tubular
wall of fixed axial length; has at least one proximal end for entry; has at
least one
distal end for egress; and has at least one internal Iumen of a volume
sufficient to
, allow for on-demand controlling passage therethrough of a prepared abturator
carrying a deformable thermoelastic cuff and a bypass conduit.
Catheters, particularly surgical catheters, are conventionally known and
used; and a wide range and variety of guiding or introducer catheters are
available
which are extremely diverse in shape, design, and specific features. All of
the
essential requirements of a guiding flexible catheter exist as conventional
knowledge and information in the relevant technical field; and all of the
information regarding catheter design and provided in summary form hereinafter
is
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publicly known, widely disseminated, and published in a variety of
authoritative
texts. The reader is therefore presumed to be both familiar with and have an
in-
depth knowledge and understanding of the conventional diagnostic and
therapeutic
uses of catheters and catherdzation techniques. Merely representative of the
diversity of publications publicly available are the following, each of which
is
expressly incorporated by reference herein: Dia n~ostic end Therapeutic
Cardiac
Cathertization, second edition (Pepine, Hill, and Lambert, editors) Williams &
Wilkins, 1994 and the references cited therein; A Practical Guide To Cardiac
Pacing, fourth edition (Moses ~. ~1., editors) Little, Brown, and Company,
1995
and the references cited therein; Abrams Angiogranhv, third edition (H. L.
Abrams, editor), Little, Brown, and Company; 1983.
A number of specific types of guiding catheters or introducers are known
today; but for purposes of practicing the present invention, a number of newly
designed or specifically designed catheters of varying lengths and sizes
suitable for
IS bypass use are expected and intended to be developed and manufactured
subsequently. Equally important, minor modifications of the presently existing
general categories of catheters are equally appropriate and are expected to be
found
suitable for use when practicing the present invention. Accordingly, a summary
review of the conventionally known catheter types as well as a overall
description
of general catheter design and the principles of catheter construction are
presented
herein.
Catheter construction and design:
Presently known specific types of catheters include the following: central
_ venous catheters which are relati ely short (usually 20-60 centimeters) in
length
and are designed for insertion into the internal jugular or subclavian vein;
right
heart catheters such .as the Cournard catheter designed specifically for right
heart
catheterization; transseptal catheters developed specifically for crossing
from right
to left atrium through the interarterial septum at the fossa ovalis;
angiographic
catheters which are varied in shape and are frequently used today in the
femorial
and brachial approach far cardiac catheterization and angiography in any of
the
major vessels; coronary angiographic catheters which include the different
series of
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grouping including Sones, Judlans, Amplatz, multipurpose, .and bypass graft
catheters; as well as many others developed for specific purposes and medical
conditions.
Merely representative of guiding and introduces catheters, generally
presented herein without regard to their specific past usages or intended
applications, are those illustrated by Figs. 1 and 2 respectively. As
exemplified by
Fig. 1, a catheter, 2 is seen having a tubular wall of fixed axial length;
having two
proximal portals 4 and 6 which together generate the proximal end 8 far entry
into
the interior of the catheter; a single distal portal 10 and the distal end 12
of the
catheter; and an internal lumen 14 (which is not visible in the illustration).
Another variation commonly known is illustrated by Fig. 2 which shows a
controlling flexible catheter 20 having a tubular wall of fixed axial length;
three
proximal portals 21, 22 and 23 respectively which collectively form the
proximal
end 24 for entry into the internal volume of the catheter; and a single distal
portal
25 which designates the distal end 26 or tip of the catheter. It will be
appreciated
and understood that Figs. 1 and 2 are presented merely to show the overall
general
construction and relationship of parts present in each flexible controlling
catheter
suitable for use with the present methodology:
In accordance with established principles of conventional catheter
construction, the axial length of the catheter may be composed of one or
several
layers in combination. In most muldlayered constructions, one hollow tube is
stretched over another to form a bond; and the components of the individual
layers
determine the overall characteristics for the catheter as a unitary
construction.
Most multilayered catheters comprise an inner tube of teflon, over which is
another
25. layer of nylon, woven Dacron, or stainless steel braiding. A tube of
polyethylene
or polyurethane is then heated and extruded over the two inner layers to form
a
bond as the third external layer. Other catheter constructions may consist of
a
polyurethane inner core, covered by a layer of stainless steel braiding, and a
third
external jacket layer formed of polyurethane:
Several examples of basic catheter construction and design are illustrated by
Figs. 3-6 respectively. Figs. 3A and 3B are perspective and cross-sectional
views
of a single tubular wall considered the standard minimum construction for a
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catheter. Figs. 4A and 4B are perspective and cross-sectional views of a thin-
walled design for a single Iayer extruded catheter. In comparison, Figs. SA
and
SB are perspective and cross-sectional views of a standard multilayered
catheter
construction having a braided stainless steel midlayer in its construction.
Finally,
Figs. 6A and 6B are perspective and cross-sectional views of a thin-walled
design
for a multilayered catheter with a braided stainless steel middle layer.
Catheters are generally sized by external and internal diameter and length.
The internal specified either by diameter (in thousandths of an inch or
millimeters
or French). Many newer thin-walled catheter designs provide a much larger
IO internal lumen volume to external diameter ratio than has been previously
achieved; and this has resulted in catheters which can accommodate much more
volume and allow the passage of much larger sized articles through the
internal
lumen. External diameter is typically expressed in French sizes which are
obtained
by multiplying the actual diameter of the catheter in millimeters by a factor
of 3Ø
IS Conversely, by traditional habit, the size of any catheter in millimeters
may be
calculated by dividing its French size by a factor of 3Ø French sizes from 5-
8
are currently used for diagnostic angiography. For purposes of practicing the
present invention, it is also desirable that French sizes ranging from 4-16
respectively be employed unless other specific size requirements are indicated
by
20 the particular application or circumstances. In addition, because of the
variation
between standard, thin-walled, and super high-flow catheter construction
designs, a
range and variety of external and internal lumen diameter sizes exist. To
demonstrate the conventional practice, the data of Table 1 is provided.
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Dual-lumen catheter:
A number of different dual-lumen catheters are known today which differ in
the size and spatial relationship between their individual lumens. This is
illustrated
by Figs. 7A-7D respectively which show different dual-lumen constructions for
four catheters having similar or identical overall diameter (French) size.
As shown therein, Fig. 7A shows a dual-lumen catheter 30 wherein a first
external tubular wall 32 provides an outer lumen volume 34 into which a second
internal tubular wall 36 has been co-axially positioned to provide an inner
lumen
volume 38. Clearly; the construction of catheter 30 is a co-axial design of
multiple
tubular walls spaced apart and co-axially spaced but separate internal lumens
of
differing individual volumes.
In comparison, Fig. 7B shows a second kind of construction and design by
dual-lumen catheter 40 having a single external tubular wall 42; and an
centrally
disposed inner septum 44 which divides the interior tubular space into two
approximately equally lumen volumes 46 and 48 respectively. Thus, in this
construction, the diameter, length, and volume of internal lumen 46 is
effectively
identical to the diameter, length and volume of internal lumen 40; and both of
these exist and are contained within a single, commonly-shared, tubular wall.
A third kind of construction is illustrated by Fig. 7C and shows an
alternative kind of construction and design. As seen in Fig. 7C, dual-lumen
catheter 50 has a single external tubular wall 52; and contains an
asymmetrically
positioned internal divider 54 which divides the interior tubular space into
two
unequal and different lumen volumes 56 and 58 respectively. Thus, in this
alternative construction, the discrete volume of internal lumen 56 is markedly
25. smaller than the volume of the adjacently positioned internal lumen 58;
and yet
both of these internal lumens Sb and 58 exist in, are adjacently positioned,
and are
both contained within a commonly-shared single tubular wall.
A fourth construction and design for a dual-lumen catheter is presented by
Fig. 7D which shows a catheter 60 having. a single external tubular wall 62 of
relatively large size and thickness. Within the material substance 68 of the
tubular
wall 60 are two discrete bore holes 64 and 66 of differing diameters which
serve as
two internal lumens of unequal volume. Internal lumen 64 is clearly the
smaller
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while internal lumen 66 is far greater in spatial volume. Yet each internal
lumen
volume 64 and 66 is adjacent to the other, lies in parallel, and follows the
other
over the axial length of the catheter.
Introducer catheter anc~ ~;,~theter ends:
In general, an introducer catheter is straight or linear over ifs axial length
and does not have any bends or curves towards the distal end or at the distal
tip.
A representative illustration of the distal end and tip of an introducer
catheter is
shown by Fig. 8.
As seen in Fig. 8, an introducer catheter 80 has an elongated tubular body
82 formed by a cylindrical-shaped sidewall 84 and provides a hollow internal
lumen 86 which extends over its linear axial length. The catheter distal end
88
terminates as a single tip 90 having one central distal portal 92 to the lumen
86.
Similarly, the catheter proximal end 94 terminates as an enlarged proximal tip
96
and has one central proximal portal 9$ to access the internal lumen 86.
Conventional practice also permits a number of different distal ends or tips
which vary in design and appearance to be used with any given style or type of
catheter. Merely representative of these permitted and conventional variances
in
distal end design for catheters generally are the distal ends of some
ventricular
catheters which can include a "pigtail" design and construction which has a
curled-
tip format and multiple side holes; the Lehman ventricular catheter end which
provides a number of side holes in different places along the distal end; and
the
Gensini design which provides multiple side holes at varying angles.
Accordingly,
for purposes of practicing the present invention, any construction of the
catheter
distal end whether having one or more curves, or none; and whether or not
there is
more than one central portal for exiting the lumen or multiple side holes, are
all
considered conventional variations in catheter tip construction and design.
Any and
all of these distal tip designs and constructions are therefore deemed to be
encompassed completely and to lie within the general catheter scope of
construction
suitable for use with the present invention.
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B. The Obturator
The second requisite component part of the catheter apparatus is the
obturator. Each embodiment of an obturator is comprised of at least three
parts,
and preferably comprises four component parts. The minimal requisite three
elements include a puncturing headpiece; a perforating end tip on the
headpiece; an
elongated shaft integral with the puncturing headpiece. The fourth highly
desirable
component is the means for expanding and contracting the size of the
puncturing
headpiece on-demand. Various embodiments representative of each of these
structural components are individually illustrated within Figs. 9-15
respectively.
One general embodiment of an obturator is illustrated by Figs. 9-10. As
seen therein, the obturator 120 comprises a puncturing headpiece 122 which is
substantially bullet-shaped (frusto-conical) in configuration, and comprises
an outer
shell 124 and a base plate 126. The outer shell 124 has determinable surface
dimensions and an overall girth which can be either axed or varied in size. At
the
I5 distal end 128 of the puncturing headpiece 122 is a perforating end tip 130
which
appears as a cross-shaped cutting edge for the headpiece 122. As shown by Fig.
10, the perforating end tip 130 does not extend over the entire surface area
of the
outer shell 124; instead, the perforating end tip 130 is limited in size and
orientation to the distal end 128. The perforating end tip I30 serves as the
sharp
cutting edge for the obturator 120 as a whole.
Integral with the puncturing headpiece 122 is an elongated shaft 134 whose
overall axial length may be varied to accommodate the surgeon and the
particular
medical circumstances of usage. The distal end 136 of the shaft is integrated
with
the puncturing headpiece 122 and can provide access to the interior volume o.f
the
25. headpiece bounded by the outer shell 124 and the base plate 126. The
proximal
end 138 of the elongated shaft 134 is intended to be held by the surgeon
performing the vascular bypass surgery. Accordingly, the axial length of the-
elongated shaft I34 will vary and accommodate the surgeon; and thus vary from
a
few inches to a few feet in length. The function of the elongated shaft 134 is
for
the carrying and transport of a bypass conduit to the chosen site on the
unobstructed or primary blood vessel in-vivo. The elongated shaft 134 acts to
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support, maintain and convey the conduit within the lumen of the catheter in a
manner such that the conduit can be used as a bypass graft.
The fixed size gmbodiments of the obturator
The minimalist format for the obturator does no provide any means nor
mechanism to alter the surface dimensions or configuration of the puncturing
headpiece integrated with the elongated shaft. Thus, the initial dimensions
and
girth for the puncturing headpiece 122 shown by Figs. 9 and 10 respectively
will
remain constant and fixed; and neither the size, shape, aspect ratios, nor
overall
geometry will be changed or modified during the intended in-vivo use for the
obturator embodiment. The fixed size embodiment; however, is a less preferred
format for clinical applications; and this minimalist format may cause more
procedural difficulty and inconvenience for the surgeon than the preferred
variable-
size embodiments of the obturator.
The variable-size embodiments of the obturator
A highly desirable and preferred component feature of the puncturing
headpiece and the obturator as a whole is that means exist for expanding and
contracting the puncturing headpiece on-demand. The effect of this fourth
feature
and capability for the obturator is illustrated by Figs. 11-13 respectively.
As seen
within Fig. 11, the puncturing headpiece 122 appears in its initial size
identical to
that shown by Figs. 9 and 10. The outer shell 124 is substantially cone-shaped
in
configuration, has an initial internal volume, and has a girth dimension d
equal to
the initial diameter of the base plate 126. The internal volume of the
puncturing
headpiece, as determined by the dimensions of the outer shell 124 and the base
plate 126, provides an initial internal volume of determinable quantity:
When the mechanism for contracting the puncturing headpiece is activated,
the consequence is illustrated by Fig. 12 in which the dimensians of the outer
shell
124 have been diminished and the girth of the headpiece has been reduced as
shown by the reduced diameter d' of the base plate 126. Note also, that as the
puncturing headpiece 122 becomes contracted in overall volume and dimensions,
the configuration of the puncturing headpiece 122 has consequentially become
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altered and now appears to be spear-like in configuration. Similarly, the
overall
angular disposition of the perforating end tip 130 serving as the cutting edge
will
also be slightly altered in overall appearance as a consequence of contracting
the
puncturing headpiece 122.
Alternatively, when the puncturing headpiece 122 is expanded, the overall
result is shown by Fig. 13. As seen therein, the outer shell 124 has been
expanded
in overall dimensions and volume; and the girth of the headpiece has been
expanded and can be determined by the diameter d" of the expanded base plate
126. Note that the overall appearance of the puncturing headpiece has been
altered
as a consequence of its expansion and now appears to be elliptical in shape
overall.
Similarly, the perforating end tip 130 has similarly been altered in
appearance and
has angularly expanded somewhat to conform with the expanded dimensions and
angularity of the outer shell 124.
It will be recognized and appreciated also that throughout the changes in
appearance, internal volume (designated as V, V' and V") and overall size for
the
contracted or expanded puncturing headpiece 122 (as shown via Figs. 11, 12,
and
13 respectively), the dimensions and overall configuration of the elongated
shaft
134 have not been altered meaningfully or significantly. Although this is not
an
absolute requirement in each and every embodiment of an obturator, it is
preferred
that the elongated shaft 134, particularly at the integrated distal end 136,
remain
constant in size and volume as much as possible and be unaffected subsequent
to
the on-demand expansion or contraction of the puncturing headpiece 122. This
preference and feature will maintain the integrity of the synthetic prosthesis
or the
excised vascular segment intended to be carried and transported by the
elongated
shaft during the bypass grafting procedure. Thus, to avoid or minimize any
physical damage to the graft material, it is desirable that the elongated
shaft be
maintained in appearance, configuration and dimensions without change whenever
possible.
Means for contracting or expanding,the puncturing headpiece
A feature and component of each preferred obturator is the existence and
availability of specific means for expanding and contracting the puncturing
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headpiece on-demand. A number of different mechanisms and means for
expanding and contracting the puncturing headpiece of the obturator are
conventionally known and easily employed. Merely to demonstrate some different
and conventionally known mechanisms, attention is directed to the means
illustrated
by Figs. 14 and 15 respectively.
The means for expanding and contracting the puncturing headpiece on-
demand illustrated by Fig. 14 constitute a mechanical approach and design
mechanism which is carried within the internal volume of the puncturing
headpiece
122 and the integrated elongated shaft 134. As seen therein, a central rod 150
extends through the hollow interior of the elongated shaft 134 and extends
into the
internal volume defined by the outer shell 124 and the base plate 126 of the
puncturing headpiece 122. Within the internal volume of the outer shell 124, a
plurality of rotable ribs 152 are joined to the central rod 150 at the distal
end to
form a central pivot point 154. Fach rotable rib 152 is mobile and pivotable
around the central point 154 and forms an umbrella-like scaffolding structure
which
can be expanded outwardly or collapsed inwardly at will. Mounted on the
central
rod 150 is an expansion wheel 156. This expansion wheel 156 is centrally
mounted on the rod 150; is moveable over the axial length of the central rod
150;
and is controlled in the direction of axial movement {distally and
proximally). The
expansion wheel 156 comprises a center hub 158 and a plurality of hub supports
160, both of which maintain the expansion wheel in proper position as it
engages
the plurality of rotable ribs 152. Joined to the central hub 158 of the
expansion
wheel 156 are linear movement members 162 which are positioned within the
interior volume of the elongated shaft 134 and have a length sufficient to
reach to
the proximal end 138 of the elongated shaft 134 for control by the surgeon or
invasive radiologist. The linear movement members 162 engage the center hub
158 of the expansion wheel 156; and extend or withdraw the expansion wheel
closer to or away from the perforating end tip 130 of the puncturing headpiece
122. When the expansion wheel is engaged and pushed forward, expansion wheel
engages the rotable ribs 152 and expands the rotable ribs outwardly thereby
increasing the overall girth of the puncturing headpiece as a unit.
Alternatively,
when the linear movement members 162 are withdrawn, the expansion wheel
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recedes towards the proximal end and the engaged rotable ribs 152 collapse
inwardly within the volume of the outer shell 124. The consequence of this
movement is a contraction of the puncturing headpiece 122 as a unit. It will
be
recognized and appreciated that this mechanical approach for expanding and
contracting the puncturing headpiece is completely conventional in design and
operation; and accordingly, any conventional refinement of these basic
component
parts is considered to be a variation within the scope of this mechanical
system.
As a representated alternative, hydraulic means for expanding and
contracting the puncturing headpiece of the obturator on demand is also
provided.
In this system, as shown by Fig. 15, the internal volume of the puncturing
headpiece I22 and the integrated elongated shaft 134 includes an elastic sack
180
comprised of a fluid containing elastic bubble 182 and a fluid delivering
elastic
conduit 184. The outer shell 124 and base plate 126 of the puncturing
headpiece
122 are as previously shown; and the headpiece 122 is integrated with the
elongated shaft I34 as previously described herein. Within the internal volume
of
the puncturing headpiece 122, is a fluid containing elastic bubble 182 which
is in
fluid communication with the elastic conduit 184 carried within the internal
volume
of the elongated shaft 134. The elastic sack 180 is formed of elastomeric
material
(such as rubber, elastic plastic, and the like) and is fluid-tight along its
seams. The
elastic sack 180 contains any liquid which is compatible with the material of
the
elastic sack; and it is the intrinsic nature of the material forming the
elastic sack
180 that the material exerts a compression force or pressure upon the fluid
contained within the elastic sack itself. In this way a hydraulic system for
expanding and contracting the puncturing headpiece of the obturator is
created.
As fluid is introduced through the elastic conduit 180 by the surgeon or
invasive radiologist, that fluid is conveyed and delivered into the elastic
bubble 182
positioned within the puncturing headpiece 122. The elasticity of the bubble
182
exerts a mild compression force and pressure against the quantity of fluid
contained
within the bubble interior volume; accordingly, the greater the quantity of
fluid
within the elastic bubble 182, the larger in overall volume the elastic bubble
becomes. Thus, as more fluid is delivered through the conduit 184 into the
elastic
bubble 182, the larger in overall volume the elastic bubble becomes; and as
the
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volume of the elastic bubble expands, the overall configuration and internal
volume
of the piercing headpiece 122 also enlarges. In this manner, by carefully
controlling the amount of fluid conveyed through the conduit 184 into the
elastic
bubble, the overall size and configuration of the piercing headpiece 122 can
be
controllably expanded. Subsequently, to reduce the overall size and
configuration
of the puncturing headpiece 122, a quantity of fluid is permitted to be
released
from the elastic conduit 184 at the proximal end by the surgeon or
radiologist.
Because the material is elastic and exerts a compression force against the
quantity
of fluid present within the bubble at any given moment in time, the release of
fluid
through the elastic conduit will cause a reduction in overall size for the
elastic
bubble 182; and as the overall volume of the elastic bubble is reduced in
size, the
puncturing headpiece will consequently be contracted and reduced in
configuration
and overall volume as well. It will be noted and appreciated also that this
hydraulic mechanism for expanding and contracting the puncturing headpiece an
demand is a conventionally known fluid system and technique; and many
conventionally known variations and changes in hydraulic design and fluid
control
systems are presently known and commonly available for use. Accordingly, all
hydraulic systems are envisioned as suitable for use as one means for
expanding
and contracting the puncturing headpiece of the obturator on-demand.
Ai~ernative obturator stru~~ures
A number of different physical embodiments for the obturator are also
envisioned and intended for use. Some examples, which are merely illustrative
of
the range and variety of physical formats and which serve to merely illustrate
the
range and degree of difference available for the various puncturing headpieces
of
an obturator, are illustrated by Figs. 16-22 respectively. It will be
recognized and
understood, however, that these alternative embodiments are merely
representative
of obturators and puncturing headpieces generally and do not signify any
limitation
or restriction on their structural construction or design.
The embodiment illustrated by Figs. 16 and 17 respectively shows a
puncturing headpiece 200 which is substantially cone-shaped in overall
appearance
and comprises an outer shell 202 and a base plate 206. The distal end 208 of
the
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puncturing headpiece 200 has a perforating end tip 210 which is also
substantially
cone-shaped in configuration and appearance and covers only a small surface
area
of the outer shell 202. Integral with the puncturing headpiece is the
elongated
shaft 134 as described previously herein; and means for,expanding and
contracting
the puncturing headpiece 200 on-demand are included within the obturator as a
integrated unit.
Another embodiment for the puncturing headpiece is illustrated by Figs. 18
and 19 respectively. As shown therein, the puncturing headpiece 220 comprises
the outer shell 222 and the base plate 224 integral with the elongated shaft
134. A
particular feature of this embodiment, however, is the distal end 226 seen
most
clearly within Fig. 19 as providing a perforating end tip 230 which is
substantially
star-shaped and extends over the surface area of the outer shell 222. The
result is
to provide a series of grooves 228 alternating with sharp cutting edges 232
over the
surface of the outer shell 222. This embodiment for the puncturing headpiece
220
I5 provides a much greater area for cutting and perforation as a specific
feature of the
obturator design.
To demonstrate further the variety and degree of differences envisioned and
intended when constructing a puncturing headpiece, the structural
constructions
exemplified by Figs: 20-22 respectively are provided. As illustrated by Fig.
20,
the puncturing headpiece 250 includes a buttressing region 254 as a part of
the
outer shell 252. The buttressing region 254 is a reinforced region for
engaging
materials placed in contact with the outer shell when the puncturing headpiece
is
expanded. The puncturing headpiece 250 includes a base plate 256 and is
integrated with the elongated shaft 134 (described previously herein).
25, in comparison, the puncturing headpiece 260 exemplified by Fig. 21 is a
sharply tapered and contoured embodiment in which the outer shell 262 includes
a
spiral girth zone 264 suitable for deforming elastic materials. The base plate
266
conforms to and is integrated with the spiral zone 264.
Another alternative embodiment of the puncturing headpiece is illustrated by
Figs. 22A and 22B. In this embodiment, the puncturing headpiece 280 comprises
an outer shell 282 having a triangular-shaped distal tip 284 which is joined
to and
integrated with the base plate 286 and the elongated shaft 134. The triangular-
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shaped configuration of the distal tip 284 is intended to aid the puncturing
headpiece as it is expanded and contracted on-demand.
II. 'The Deformable Thermoelastic Cuff
An essential component part of the apparatus and method for creating a
bypass graft is the presence and use of a deformable thermoelastic cuff
comprised
of a shape-memory alloy composition and prepared in advance to deform in a
warm temperature environment.
The shape-memory metal alloy compositions to be used with the present
invention constitute conventionally known blends and formulated metallic
mixtures
of nickel and titanium which undergo a phase transition -- that is, a
molecular
rearrangement of atoms, molecules or ions within a lattice structure -- as a
consequence of an increase in temperature. The unique capability of shape-
rnemory alloys is that these alloys after pretreatment will change shape or
IS configuration in whole or in part as a direct consequence of a change in
temperature; and the alloy composition "remembers" its earlier pretreatment
and
specifically prepared shape because the temperature-initiated phase change
affects
its structure on the atomic level only, without disturbing the arrangement of
the
molecules which would otherwise be irreversible.
When these shape-memory alloys are intentionally superheated far above
their individual transition temperature (either electrically or by external
heat), in a
preselected shape, a stretched temperature-transformed alloy format results
which
contracts and exerts considerable force; and the temperature-transformed alloy
composition becomes memory-shaped in that fixed specific configuration as a
permanent feature. Afterwards, when cooled to below its transition
temperature,
the heat pretreated or prepared alloy composition can then be bent and
reshaped
into other chosen extant configurations while retaining nevertheless the fixed
"memory" of the particular prepared shape in the earlier superheated
condition.
Thus, these shape-memory alloy compositions are recognized as being malleable
into any chosen extant form, shape, or configuration after pretreatment in the
superheated condition; as being both deformable and thermoelastic; and as
being
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able to revert into a prepared memory-shaped configuration merely by being
warmed to a temperature above its individual transition temperature.
Allov formulations
At least twenty different formulations of these alloys are conventionally
known to exhibit the shape-memory effect and property, all of these comprising
different mixtures of nickel and titanium in varying percentage ratios Desi n
ew , 3une 21; 1993 issue, pages 73-76]. These metal alloys are today utilized
in
the manufacture of differing products. For example, a range of different shape-
memory alloy wires are commercially available in diameters from 0.001-0.030
inches (Dynalloy Inc., Irvine, California]. In addition, surgical anchors
having
superelastic properties and farmed by two or more arcs of wire strands (which
can
withstand strains exceeding I0% ) have been developed [Mitek Surgical
Products,
Inc., Norwood, Massachusetts]. Also, blood clot filters formed of shape-memory
alloy wires are commercially sold for implantation in large blood vessels such
as
the vena cava (Nitinol Medical Technologies, Inc., Boston, Massachusetts].
While
these commercially available products illustrate the use of one or more shape-
memory alloy formulations by the manufacture of their particular articles, a
more
general listing of conventionally known properties and characteristics for
shape-
memory alloy compositions is provided by Table 2 below.
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Table 2:
Conventionally Known Properties Of Shape-Memory Alloys'
Transformation Properties
Transformation Temperature.:.:.............. -200 to 110°C
Latent Heat Of Transformation............... 5.78 callg
Transformation Strain (for polycrystaline material)
for a single cycle ............................ 8% maximum
z
for i0 cycles ...............................:... 6%
for 105 cycles ................................... 4%
Hysteresis* ...... .................................... 30 to 50°C
Physical Properties
Melting point ..........................................1300C (2370F)
Density ................. ..............................6.45 g/cm' (0.0233
lhlin')
Thermal Conductivity
austenite .................. ...................,Ø18 Wlcm ~ C
(10.4 BTU/ft ~ hr
~ F)
0
martensite .......................................Ø086 Wlcm ~ C
{5.0 BTU /ft. ~ F)
Coefficient of Thermal Expansion
6 0 { -6 0 )
austenite ..........................................11.9x10' I C 6.11x10
I F
martensite ....,..........:.........................6.6x10'~lC (3.67x10'/F)
0
Specific Heat .........................................Ø20 cal/g ~ C
{0.20 BTU/ib ~ F)
Corrosion Performance** .......,...............excellent
Electrical Properties
Resistivity (p}
[resistance = p ~ length/cross-sectional
area]
austenite ....................................'100 ~cS'2 ~ cm ('39.3
~rC2 ~ in}
martensite ....... . ........................'80 ~t2 ~ cm ('31.5
~cSZ ~ in)
Magnetic Permeability .....................< 1.002
Magnetic Susceptibility ........ .........3.0x 106 emu/g
Mechanics! Properties
Young's Modulus***
austenite ......................................... '83 GPs (' 12x 106 psi)
martensite .................:..................... '28 to 41 GPs ("4x106 to
6x106 psi}
Yield Strength
austenite ................................:........ 195 to 690 MPs (28 to 100
ksi}
martensite ....................................... 70 to 140 MPs (10 to 20
ksi)
Ultimate Tensile Strength
fully annealed .................................. 895 MPs {130 ksi}
work hardened ..........................,..... 1900 MPs (275 ksi)
Poisson's Ratio ..................................... 0.33
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Tabie 2 (continued):
Conventionally Known Properties Of Shape-Memory Ailoysi
Mechanical Properties (continued)
Elongation at Failure
fully annealed ..................................25 to 50%
work hardened .......................:........5 to 10%
Hot Workability ......................................quite good
Cold Workability ....................................difficult due to rapid
work
hardening
Machinability .......................................difficult, abrasive
techniques are
preferred
* Values listed are for a full martensite to austenite transition. Hysteresis
can be
significantly reduced by partial transformation or ternary alloys.
** Similar to 300 series stainless steel or titanium.
*** Highly nonlinear with temperature.
I Design News, June 21, 1993 issue, p.77.
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All the different specific formulations and metallic blends comprising nickel
and titanium which yield a deformahle, thermoelastic, shape-memory alloy
composition are suitable for use when practicing the present methodology. AlI
of
these shape-memory alloys rely on a crystal phase change from a higher
temperature Austenite form to a lower temperature Martensite form to
accomplish
the memory effect. The cubic Austenite phase behaves much like ordinary metals
as it deforms. In contrast, the complex crystal Martensite form can be found
by
reversible movement of twin boundaries to change the average "tilt" or strain
in
each segment of the alloy. The overall strain can be eliminated by releasing
the
stress, by maintaining it if it is not thermally stable (the superelastic
effect), or by
heating the alloy to change it back to Austenite form (shape-memory effect).
The crystal transformation of shape-memory alloy compositions is, by
definition, thermoelastic - i~ it progresses in one direction on cooling below
the
transition temperature and in the other direction upon heating above the
transition
temperature. The amount of transformation change versus temperature, measured
either as the present Martensite form or the strain in a constantly stressed
element,
is a function of and can be plotted against temperature (°C) directly;
and the
change from one phase (and identifiable shape) to another typically occurs in
a
narrow temperature range (often 5-10°C). Hysteresis takes place before
the reverse
transformation occurs.
The amount of strain accommodated due to the movement of twin
boundaries, differs in each metallic alloy blending system. In the nickel-
titanium
system for example, up to 8 % reversible tensile strain is available; however,
to
guarantee a long life use, the strain is often limited to 4-5 % .
The stress-strain behavior of shape-memory alloy compositions is employed
to help explain the shape-memory effect. For instance, the Martensite form is
much easier to deform than Austenite. Therefore, one can deform the alloy with
much less force to change it back into Austenite form. As a result, the alloy
converts thermal energy to mechanical work at high forces.
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Fixing the memory-shaped configuration in the metal alloy
To prepare and fix the particular (or desired) shape to be "remembered"
when the alloy underg~s a temperature phase transition, the alloy composition
must be superheated initially to about 300-600°C for between 30 minutes
- 3 hours
while held in the shape and position to be memorized. wring the superheating
process, the native alloy blend enters what is called the Austenite phase -- a
rigid
lattice of nickel atoms surrounded by titanium alloys. Then; as the alloy
metal
cools below its transition temperature (which will vary with the percentage
proportions of nickel and titanium), the alloy composition adopts the
Martensite
phase in which the nickel and titanium atoms assume a very different
arrangement
-- one that is flexible and malleable, and is thus very easy to bend. The
cooled
and pretreated metallic alloy can then be reshaped into any other extant
configuration or orientation repeatedly. Nevertheless, when the metallic alloy
is
subsequently warmed or heated to the chosen transition temperature range
between
25-35°C, thermal motion causes the atoms to snap back into the
Austerine phase,
thereby restoring the previously fixed memory-shaped configuration of the
abject.
Also, when the alloy is warmed above its transition temperature the form
becomes
firm and rigid in configuration [Invention & Technology, Fall 1993, pages 18-
23] .
For purposes of practicing the present in-vivo repair methodology, it is
most desirable that the shape-memory alloy composition be prepared in a
metallic
blend and formulation such that the temperature transition phase occurs at a
temperature less than about 35°C; but greater than about 25°C;
and preferably be
in the range from about 30-35°C. This preferred 30-35°C
transition phase
temperature range is dictated by the demands of the human body which maintains
a
normal temperature at about 37°C (98:6°F); and typically shows a
normal
temperature range and variance of one or two degrees Celsius above andlor
below
this normative temperature standard. It is for this reason that the broad
temperature range be about 25-35°C and the preferred temperature
transition occur
in the range of 30-35°C; but that such transformation into the prepared
fixed
memory-shaped configuration occur at least by a temperature of 35°C to
insure a
safety margin of medical usefulness.
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The alloy cuff structure and embodiments
The alloy cuff is embodied generally an open-ended and elongated article of
manufacture; is often cylindrical, ovoid; barrel-shaped, tube-like or spiral
in
appearance; and has a substantially rounded cross-section which typically is
S circular, oval, or oblong in geometry. The cuff article is ostensibly hollow
over its
axial length; and is dimensioned in overall diameter size and axial length to
accommodate and to contain comfortably the graft segment (intended to be used
as
a blood conduit) within and through the spatial volume of the cuff's hollow
interior.
It is both desirable and most preferred that the alloy cuff structure be an
open-weave pattern of wires composed of a memory-shape alloy rather than be a
solid mass of thermoelastic alloy material. For this reason, all the preferred
cuff
embodiments presented herein appear as an open meshwork of wires which are
intertwined in any of a wide variety of diverse patterns; can have regular or
irregular points, edges, and ends; provide symmetrical or asymmetrical
contours
and perimeters; and can be consistent or inconsistent in meshwork format and
pattern. The open meshwork of wires for the cuff structure provides the
desired
degree of resiliency, flexibility, and memory-shaped deformation capability
for
optimal results.
Merely representative of the typical wire meshwork patterns which are
available for use in the body of the cuff structure are those illustrated by
Figs. 23-
28 respectively. Each representative wire meshwork pattern suitable for use
a.s the
cuff body is shown in an overhead view and in a cross-sectional view. Thus,
Figs.
23A and 23B illustrate a squarelirte pattern for the wire meshwork while Figs.
24A
25, and 24B show a large-box meshwork pattern. Alternatively, Figs. 25A and
25B
reveal a nets pattern of wires while Figs. 26A and 26B demonstrate a brick
pattern
of wire weaving. Finally, Figs. 27A and 27B depict a spire meshwork pattern
while Figs. 28A and 28B portray a honeycomb pattern.
In addition, the cuff structure provides the user with a choice and variety of
different open end surfaces, edges, contours and perimeters regardless of the
particular wire meshwork pattern employed in the body of the cuff.
Representative
of some typical open-ended designs and perimeter surfaces for the alloy cuff
are
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those shown by Figs. 29, 30, and 31 respectively. Fig. 29 illustrates a smooth
and
regular perimeter surface and circular open-end for the cuff. In comparison;
Figs.
30A and 34B show two different types of finished open ends which are petaloid
points in appearance and edge design. Alternatively, Fig. 31 depicts a set of
single
stranded, bare-wire points as the open-end and perimeter edge of the cuff
structure.
Note also that there is no requirement or demand that each of the two open
ends in
any alloy cuff structure be identical or similar in end design or perimeter
appearance. Thus, merely as an exemplary instance in a single alloy cuff
embodiment, a first open end may take form as the petaloid points of Fig. 30A
while the other second open end may appear as the bare wire points of Fig. 31.
Moreover, it is also intended that any of the representative wire meshwork
patterns suitable for use in the body of the cuff as illustrated by Figs. 23-
28 may
utilize and employ any or aII of the typical open end structures and designs
shown
by Figs. 29-31 respectively. Thus, by merely using those examples provided by
Figs. 23-31 inclusive, the permutations and combinations of available cuff
body
and cuff open end choices provide 36 cuff embodiment possibilities. Many, many
more cuff structure embodiments are available using conventional choices of
other
wire meshwork patterns and open-ended formats which are known and often
commercially sold in the technical field.
The extant shape and the memory-shaped deformed configuration
It is intended and expected that the alloy cuff article {preferably embodied
as open-weave meshwork pattern of wires having two open ends) will exist in
two
different states and contours, which are: the extant shape, state, and
transitory
25, outline appearing at ambient temperatures less than about 25-35°C;
and the
memory-shaped, deformed configuration state prepared in advance and appearing
as a consequence of exposure to ambient temperatures greater than about 25-
35°C.
The range and variety of some useful extant shapes and memory-shaped
configurations is described in detail hereinafter.
By definition, the extant state and transitory shape or appearance is that
outline and contour for the cuff which exists at least immediately prior to
positioning the cuff over the bypass graft segment; and is the elongated and
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generally unbent appearance imposed on the cuff article of manufacture
subsequently after the alloy has been prepared in advance (thus leaving the
memory
of a specific configuration permanently imprinted into the alloy composition).
The
extant shape can be manipulated and changed at will so long as the ambient
environment temperature remains below 25-35 °C, the critical transition
temperature range for the alloy composition. Thus the extant shape can be
intentionally or accidentally bent or twisted and then unbent and untwisted if
desired, once or on multiple occasions. Similarly, the extant shape can and
undoubtedly will be altered or rearranged in whole or in part to fit over,
accommodate, and ultimately engage the graft segment to be used as a bypass
and
blood conduit in-vivo.
The memory-shaped configuration for the prepared alloy cuff is induced and
brought into tangible form by exposure to an ambient temperature range greater
than about 25-35°C. By definition, the memory-shaped configuration is
that farm
which has been imprinted in advance into the substance of the thermoelastic
alloy
comprising the cuff article by the superheated preparatory procedure; and
constitutes the deformed state, appearance, and outline which is believed
desirable
for permanently joining a graft segment to an unobstructed blood vessel.
It is critical to recognize and understand, also, that the prepared cuff
article
-- when appearing in the extant shape and form -- need not be completely or
wholly exposed at one time to a temperature above the 25-35°C range;
and that the
structure of the alloy cuff need not become therrnoelastically deformed
entirely,
completely, or as a unitary whole at the same moment in time; and that
different
portions of the alloy cuff structure can and at-will become individually
deformed
25. into a prepared memory-shaped configuration at separate times and in
alternative
fashion. Clearly, it is intended that separate and different portions of the
improved
alloy cuff will be serially and/or sequentially exposed to temperatures
greater than
about 25-35°C; and that the consequence of each portion or section
comprising the
alloy cuff structure as a whole becoming individually exposed to a temperature
above 25-35°C will cause that component portion or section of the cuff
thermoelastically to deform into its prepared memory-shaped configuration
imprinted previously.
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'fhe configurations of the prepared alloy cuff ~t temperatures less than 25-
°C and at temperatures greater than 2S-35°~
The extant cuff configurations of the pretreated and prepared thermoelastic
alloy composition at temperatures less than about 25-35 °C (a
temperature below its
transition temperature at which the alloy exists in the Martensite phase) may
take a
broad variety of different forms, diverse dimensions, and disparate overall
shapes.
Merely exemplifying the range and diversity of three-dimensional forms into
which
the thermoelastic alloy compositions can be shaped into a cuff or flange
structure at
temperatures below 25-35°C are those illustrated by Figs. 32A, 33A,
35A, 36A,
37A, and 38A respectively. For purposes of practicing the present invention,
Figs.
32-36 are considered more preferred embodiments and constructions of the cuff-
shaped alloy structures, while Figs. 37-38 respectively represent formats and
fabrications of the alloy compositions in less frequently utilized cuff shaped
configurations.
As illustrated and embodied by Figs. 32A, 32B, and 32C respectively, the
defarmable thermoelastic cuff 300 is a substantially cylindrical-shaped
article which
is open at each of its ends 302, 304. The cuff 300 is hollow; is substantially
round or oval (in cross-sectional view}; and has an extant state and set
dimensions
at temperatures less than 25-35°C which are deformed at will into a
memory-
shaped configuration when placed at a temperature greater than about 25-
35°C.
It is most desirable that the thermoelastic material constituting the sidewall
306 of the cuff 300 be prepared and memory-shaped along the axes AA' and BB'
as shown within Figs. 32A-32C; and that the thermoelastic material
constituting the
sidewall 306 be an open-weave meshwork pattern of a memory-shaped alloy rather
25. than take form as a solid tube of material. For this reason, the sidewall
306
illustrated within Fig. 23A appears in the' first configuration as an open
meshwork
of wires which are intertwined to form a substantially honeycomb pattern shown
previously by Fig. 28. This open meshwork of wires provides a desired degree
of
resiliency, flexibility, and memory-shaped deformation capability
(particularly
along the AA' and BB' axes) such that the upper and lower portions of the
sidewall
306 will become deformed and flaired outwardly on-demand to yield the memory-
shaped configuration shown by Fig. 32C.
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It will be recognized and appreciated that the deformed cuff shown by Figs.
32B and 32C is merely the result of removing the cuff structure from a
temperature less than 25-35°C and sequentially exposing different
sections to a
temperature environment greater than about 25-35°C. Thus, solely as a
consequence of the change in temperature, the uppermost portion 308 of the
open
meshwork of wires above the axis AA' has become deformed such that the upper
sidewall 308 adjacent to the open end 302 has expanded outwardly, flaired, and
become bent into a curved lip configuration in the memory-shaped deformed
state
as shown by Fig. 32B. Note that the open meshwork of wires constituting the
central portion 310 and the lower portion 3I2 of the sidewall 306 at the other
open
end 304 remains relatively stable and substantially unaltered in its original
shape
and state. The deformation thus is controlled and the forces preferably
applied to
the upper sidewall portion from the AA' axis cause the outwardly extending,
flaired lip result. Moreover, the resulting flaired lip zone 314 retains
structural
strength and resiliency as an open meshwork of wires despite having been
created
by deformation. The ability of the cuff to be deformed in section or parts in
the
manner illustrated by Figs. 32B and 32C respectively is a requisite and
necessary
attribute and characteristic of each embodiment and construction for the
deformabie
thermoelastic cuff.
Fig. 32C illustrates the completion of the thermoelastic deformation. The
lower portion 312 of the sidewall 306 has, in its sequential turn, become
exposed
to the greater than 25-35°C temperature environment, and the lower most
portion
312 has become outwardly flaired in reciprocal fashion at the second open end
304. The deformation begins along the BB' axis and continues to the perimeter
edge outlining the open end 304.
The construction and design for the improved thermoelastic cuff in the
present invention is an example of the engineering principle that structural
form
follows intended function. As a requisite component part of the catheter
apparatus
and methodology for creating a bypass conduit in-vivo, the intended functions
of
the thermoelastic cuff are threefold in nature: {1) the temperature-deformable
cuff
is intended to engage and become joined to either a synthetic prosthesis or a
previously excised vascular segment which will serve as the bypass graft in-
vivo;
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(2) the temperature-deformable cuff is intended, to be positioned in part
within the
internal lumen of an unobstructed major blood vessel (such as the aorta) and
become thermally deformed in-situ such that a portion of the cuff wall becomes
outwardly flaired, positioned and secured within the internal lumen (the blood
flow channel) of the unobstructed blood vessel permanently; and (3) another
portion of the thermoelastic cuff is to be positioned adjacent the external
surface of
the unobstructed blood vessel and be deformed in-situ such that this other
portion
of the cuff becomes outwardly flaired and secured to the blood vessel
exterior.
Thus, as illustrated by the embodiment of Figs. 32A, 32B and 32C, the
uppermost
region 308 and the lowermost region 312 of the alloy comprising the cuff 300
are
individually deformed on-demand by warming each section individually to a
temperature greater than 25-35°C. Each section deforms into a flaired
outwardly
bent form which is intended to be secured individually to the unobstructed
artery or
vein. In comparison, the central portion 310 of the cuff is retained in
substantially
i5 unaltered farm for engagement and juncture to the graft segment which will
serve
as the bypass graft. However, the central section 310 can optionally be made
thermoelastically to increase in overall diameter slightly, if desired, in
order to
hold the cuff more tightly and to seal the vessel wall.
Several attributes and characteristics are commonly to be shared among all
embodiments and constructions of the thermally deformable memory-shaped cuff.
These include the following:
{a) It is only required that the alloy material constituting the memory-
shaped cuff be thermally deformable on-demand. For convenience and greater
facility in achieving such temperature initiated deformity in the degree and
at the
25. time required, it is most desirable that the alloy composition forming the
cuff be an
open weave or meshwork rather than a solid alloy mass, which is considered to
be
mare difficult to deform in a thermally-controlled manner. There is, however,
no
substantive restriction or limitation at any time or under any intended use
circumstances which necessitates an avoidance of a solid mass of material,
either as
a single alloy sheet or as a laminated plank of alloy material. Accordingly,
the
choice of whether to use an open meshwork or a solid mass of thermoeiastic
alloy
material is left solely to the discretion of the manufacturer and the surgeon.
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(b) The thermaelastic cuff need only be comprised of resilient; flexible,
but deformable metallic alloy matter. A number of different alloys of various
formulations may be usefully employed when making a deformable memory-shaped
cuff suitable for use with the present invention. Among the desirable alloy
formulations are those characterized by Table 2 above:
(c) After the deformable cuff has been manufactured using resilient
shape-memory alloy materials, the extant shape of the cuff structure (prior to
thermal deformation) may be covered to advantage with one or more
biocompatible coatings. These biocompatible coatings are intended to water-
tighten
the article and to facilitate the sewing of the bypass conduit to the cuff as
well as '
to reduce the interactions of the immune system and tissue reaction with the
bypass
graft after it has been secured to the blood vessels in their appropriate
locations in-
vivo. Such biocompatible coatings are conventionally known; are sometimes
incorporated with drugs such as anti-inflammation, anti-cancer, or anti-growth
.
factors or with radioactive materials; will reduce the severity and duration
of
immune or tissue reactions which frequently disrupt or interfere with bypass
grafts;
and are considered desirable in a majority of use instances in order to
minimize the
body reaction to vascular bypass surgery. Shad-memory alloys can also be made
radioactive to minimize tissue reactions. A representative listing of
biocompatible
coatings deemed suitable far use with the deformable thermoelastic cuff is
provided
by Table 3 below.
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Table 3: Biocompatible Coatings
High temperature pyrongen-free carbon;
Polytetrafluoroethylene (PTFE) and other polyhalogenated carbons;
Fibronection;
Collagen;
Hydroxyethyl methacrylates (HEMA);
Serum albumins;
Suprafilm (Genzyme Corp.);
i0 Silicone polymer;
Polyurethanes;
Tetrathane (Dupont);
Polytetramethylene polymers;
Dacron;
1S Poiyesther woven fabric; and
Polycarbonated urethanes.
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(d) ~ Although the embodiment of the memory-shaped cuff or collar prior
to thermal deformation may appear as a geometrically regular and coherent
structure, there is no requirement or demand that either the general structure
or
overall appearance of any cuff structure conform to these parameters.
Accordingly, it will be recognized and understood that neither the extant
shape nor
the shape-memory configuration need no take form as a completely encircling
band or collar of thermoelastic material. To the contrary, a U-shaped band or
flange of alloy material where the sidewall does not overlap or join and/or
where a
gapped distance separates the arms of the band or flange is both permitted and
envisioned. Moreover, although the cylindrical-shaped format of the cuff
illustrated by Fig. 32 is highly desirable, there is no requirement that the
diameter
of the cuff prior to or after thermal deformation be constant or consistent
over the
entire axial length of the cuff. Thus, anisotropic cuff structures as well as
isotropic constructions are intended and desirable. In this manner, the cuff
in its
initial state prior to thermal deformation may have a variable internal
diameter
over the axial length of the article in which one open end may be either
greater or
lesser in size than the other open end; and there may be multiple increases
and
decreases in diameter size successively over the entire axial length of the
cuff
itself. All of these variations in construction and structure are within the
scope of
the present invention.
To illustrate some of the modest variations and differences available and
envisioned for a deformable thermoeiastic cuff intended for use with the
present
invention, the alternative cuff embodiments illustrated by Figs. 33-3$ are
provided.
A particular feature is shown within Figs: 33 and 34 where the extant shape
for the
25: deformable cuff or collar 330 appears as a cylindrical-shaped article
having two
open ends 332, 334 and a rounded sidewall 336. The body of the sidewall 336 is
the pattern shown by Fig. 24 -- the large box meshwork.
A notable feature of the cuff construction within Fig. 33A is the ability to
choose the degree of outward flairing and thermal deformation at the uppermost
portion 33$ and the lowermost portion 342. The degree of deformation can be
modest and shown by Figs. 33B and 33C. However, a maximal degree of
deformation and outward bending can be prepared for the alloy in portions 33$
and
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43 _
342 in which the thermoelastic deformation is curved and convoluted to the
greatest
possible degree. This optimal alternative is illustrated by Figs. 34A-34C
respectively. In this instance, the upper most portion 338 of the cuff near
the open
end 332 and the lowermost portion 342 adjacent the open end 334 will deform
and
flair outwardly to the greatest extent possible as a consequence of placing
the cuff
in a temperature environment greater than about 25-35°C.
The result of thermal deformation in-situ of individual sections and portions
of the cuff at a temperature greater than about 25-35°C is shown by
Fig. 33C and
alternatively by Figs. 34A-34C. The sidewall upper portion 338 has become
deformed and bent from the open end 332 to about the axis AA' and the lower
sidewall portion 342 has thermoelastically deformed from about the axis BB' to
the
other open end 334. The central portion 340, however, remains substantially
unaltered. This memory-shaped configuration illustrated in the alternative by
Figs.
33C and 34A-34C is the thermally deformed state and structure suitable for
1S juncture concurrently to the internal lumen and exterior surface of an
artery or
vein in-vivo.
A third embodiment of a thermally deformable cuff or flange is illustrated
by Figs. 35A-35C. As shown therein, the extant shape and appearance for the
deformable cuff 360 is formed using the wire meshwork pattern illustrated by
Fig.
25 previously -- the nets pattern. The extant cuff 360 at temperatures less
than
about 25°C has two open ends 362, 364 and an open meshwork sidewall
361. The
open pattern of alloy wires provides the flexible and resilient meshwork
suitable
for achieving the primary functions of the memory-shaped deformable cuff. The
uppermost sidewall portion 366 has been prepared from about the axis CC' to
the
open end 362 such that the uppermost sidewall portion 366 will become bent and
deformed outwardly when exposed to an environmental temperature greater than
about 25-35 °C as shown by Fig. 35A. The lowermost sidewall 370 has
also been
prepared to deform thermoelastically from the axis DD' to the other open end
364
as shown by Fig. 35A.
The consequence of advancing the coiled cuff 360 in sections into an
ambient temperature greater than about 25-35°C is shown by Figs. 358
and 35C.
It will be appreciated that the partially-induced, memory-shaped configuration
of
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Fig. 35B is intended to be an in-situ generated result, occurring within the
internal
lumen of an artery or vein in-vivo. Accordingly, as seen in Fig. 35B, the
flaired
out uppersidewall portion 366 has become bent at nearly a 90 degree angle with
respect to the central portion 368; and the line CG' will generally serve as
the axis
of thermal deformation and curvature for the partially coiled cuff. Similarly,
when
exposed to a temperature greater than 25-35 °C, the lowermost sidewall
will deform
as seen in Fig. 35C from the axis DD' to the other open end 364. Thus, Fig.
35C
is the ultimately desired result.
The fourth alternative embodiment of a thermally deformabie cuff or collar
is illustrated by Figs. 36A-36D respectively. As seen therein, an extant shape
for
the deformable on-demand cuff 380 appears at temperatures less than 2S
°C as an
open meshwork of alloy wires in loose-weave form while the open ends 382, 384
have the petaloid design and perimeter outline as described by Fig. 30A
previously. The uppermost sidewall 386 has been prepared in advance to deform
at an environmental temperature greater than about 25-35°C to bend
outwardly
from about the axis EE' to the open end 382; and the lowermost sidewall 388
has
also been pretreated to deform thermoelastically at the elevated temperature
from
about the axis FF' to the other open end 384. These features are illustrated
by
Fig. 36A.
The consequence of placing the prepared alloy cuff 380 in sections into
temperatures greater than about the 25-35°C range is illustrated by
Figs. 36B,
36C, and 36D. As shown by Fig. 368, the open end 382 and the upper sidewall
388 of the cuff 380 have been advanced into the elevated temperature zone; and
the petaloid end perimeter has expanded and bent outwardly into the deformed
state
shown by Fig. 36D. Subsequently, as the remainder of the alloy cuff is
advanced
into the greater than 25-35°C temperature zone, the other open end 384
and
sidewall 388 also thermoelastically deform and become bent outwardly such that
the open end 384 also appears as shown by Fig. 36D. The central body portion
387 of the alloy cuff remains substantially unchanged in appearance.
A fifth alternative embodiment of a thermally deformable cuff or covering is
illustrated by Figs. 37A-37C respectively. As seen therein, an extant shape
for the
deformable on-demand cuff 390 appears at temperatures less than 25°C as
an open
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meshwork of alloy wires in loose-boxweave form while the open ends 392, 394
have the bare pointed wire end design and perimeter outline shown by Fig. 31
previously. The uppermost sidewall 396 has been prepared in advance to deform
at an environmental temperature greater than about 25-35°C to bend
outwardly
from about the axis GG' to the open end 392; and the lowermost sidewall 398
has
also been pretreated to deform thermoelasticaily at the elevated temperature
from
about the axis HH' to the other open end 394. These features are illustrated
by
Fig. 37A.
The consequence of advancing the prepared alloy cuff 390 as different
sections into temperatures greater than about the 25-35°C range is
illustrated by
Figs. 37B and 37C. As shown by Fig. 37B, the open end 392 and upper sidewall
398 of the cuff 390 have been placed into the elevated temperature zone; and
the
bare pointed wire end perimeter has expanded and bent outwardly into the
deformed state. The other end 394, however, has remained unaltered as is shown
by Fig. 37B: Subsequently, when the remainder of the alloy cuff is advanced
into
the greater than 25-35 °C temperature zone, the other open end 394 and
sidewall
398 also thermoelastically deform and become bent outwardly such that the bare
wire painted end 394 also appears as shown by Fig. 37C. Nevertheless, the
central body portion 397 of the alloy cuff remains substantially unchanged in
appearance despite the deformation at both open ends 392, 394.
A sixth alternative embodiment of a thermally deformable cuff or covering
is illustrated by Figs. 38A-38C respectively. As seen therein, an extant shape
for
the deformable on-demand cuff 400 appears at temperatures less than about
25°C
as an coiled helix of alloy wire in which the open ends 402, 404 have a single
bare
, wire endpoint as the perimeter outline. The uppermost sidewall 406 has been
prepared in advance to deform at an environmental temperature greater than
about
25-35°C to expand in size and twist in circular orientation outwardly
from about
the axis JJ' to the open end 402; and the lowermost sidewall 408 as also been
pretreated to deform thermoelastically at the elevated temperature from about
the
axis KK' to the other open end 404. These features are illustrated by Fig.
38A.
The consequence of advancing the prepared alloy cuff 400 as different sections
into
temperatures greater than about the 25-35°C range is illustrated by
Figs. 38B and
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38C. As shown by Fig. 38B, the open helical end 402 and upper helical sidewall
408 of the cuff 400 have been placed into the elevated temperature zone; and
the
bare-point wire end perimeter has expanded in size and orientation outwardly
into
the deformed state prepared in advance as the memory-shaped configuration. The
other end 404, however, has remained unaltered as is shown by Fig. 38B.
Subsequently, when the remained of the alloy cuff is advanced into the
greater than 25-35°C temperature zone, the other open end 404 and
coiled sidewall
408 also thermoelastically deform, become larger in diameter, and directed
outwardly in orientation, such that the extant helical form is entirely
deformed and
appears as shown by Fig. 38C. Clearly, in this embodiment, the central body
portion 407 of the alloy cuff 400 also has deformed in marked degree as a
consequence of being placed in the greater than 25-35°C temperature
environment.
III. The Inflatable And Deflatable On-Demand Balloon
Another unique structural feature and component of the present invention is
the presence of an inflatable and deflatable on-demand balloon preferably
positioned on and around the elongated shaft adjacent the puncturing headpiece
of
the obturator. An illustration of a preferred balloon is shown by Figs. 39-41
respectively.
As seen therein, an on-demand inflatable and deflatable elongated balloon
appears in any suitable length and girth. The balloon is desirably rounded in
overall cross-sectioned geometry; has a central lumen area or hollow center
intended for insertion and passage therethrough of the elongated shaft of the
obturator; and presents an expandable and reducible girth or diameter size
which
can be increased or decreased at will by the attending physician, surgeon, or
radiologist. The balloon may be composed of an elastic or non-elastic
material;
may be single-walled, double-walled, or mufti-walled in construction; and
comprises at least one tubular line or conduit for transporting a chosen
volume of
liquid or gaseous inflation fluid to inflate and expand the internal spatial
volume of
the balloon on-demand.
Furthermore, the balloon may optionally receive and include a guide rod,
push-pole, support tube, and/or fiber optic imaging bundle, cable or
instrument as
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an auxiliary member. Such auxiliary members will aid the actions and functions
of
the inflated balloon to achieve the intended results. In addition, a balloon
cover
may optionally be present on the obturator shaft as a thin sheath or plastic
film (not
shown) which encompasses the balloon body proper in whole or in part; and will
aid in compressing and reducing the overall size and girth of an inflated
balloon
body on-demand such that a more rapid rate of size reduction, collapse, and
deflation occurs for the balloon body under actual use conditions.
Accordingly as shown by Figs. 39A and 39B, the balloon body 420 appears
as an inflatable volumetric mass which is preferably formed as spatial
sections 424
for greater speed and control during inflation and deflation. The central
lumen 42b
is hollow and will assume a substantially rounded appearance as .the balloon
420
becomes inflated. At least one inflationldeflation flow line or conduit 428 is
present having a balloon-attached end 430 and a fluid-source end joined to a
source
of liquid or gaseous inflation fluid (not shown); the conduit 428 provides the
inflation fluid to the balloon during inflation and serves to remove the fluid
away
from the balloon's internal volume during deflation. In addition, means for
controlling and/or maintaining a desired volume of fluid within the internal
volume
of the balloon 420 are present; in this embodiment, such means take form as an
adjustable three-way stopcock 432 connected to the end of the conduit 428.
The intended placement of the inflatable/deflatable on-demand balloon 420
is shown by Figs. 40 and 41 respectively. The deflated state for the balloon
is
shown by Figs. 40A and 40B respectively. As seen therein, the deflated balloon
420 preferably rests upon, surrounds, and generally encompasses the elongated
shaft 134 of the obturator 120 in both the deflated and inflated states. A
desired
positioning for the balloon 420 is adjacent o and behind the puncturing
headpiece
122. It is also desirable that the axial dimensions of the balloon 420 resting
on the
elongated shaft 134 be sufficient in length to extend beyond the axial length
of the
prepared memory-shaped alloy cuff which is intended to be placed over the
elongated shaft 134 of the obturator 120.
The inflated state for the balloon is shown by Figs. 41 A and 41 B
respectively. The inflated balloon 421 has increased in overall dimensions as
a
consequence of liquid or gaseous fluid being conveyed to the internal volume
of
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balloon sections 424 by the conduit 428. The girth of the balloon 421 has
become
larger in cross-sectional diameter; and the actual diameter size may be either
larger or smaller than the diameter size of the puncturing headpiece 122
according
to the wishes or needs of the user: Also the central lumen 426 area has become
somewhat decreased in diameter. In addition, the axial length dimension of the
inflated balloon 421 has increased and become spread over the elongated shaft
134
of the obturator 120. Finally, when the volume of fluid within the inflated
balloon
421 is actively .or passively reduced in quantity and is removed at least in
part by
the conduit 428, the inflated balloon 421 will compress, by gravity or forced
compression means (such as a covering sheath), and revert substantially (if
not
completely) to the deflated state and size as shown in Fig. 40.
The positioned balloon may be repeatedly inflated and deflated, as needed
or desired, once or multiple times without meaningful consequence or change to
either the apparatus as a whole or the status of the patient undergoing the
bypass
procedure. The purposes and advantages offered by the positioned balloon are
multiple: (a) to provide a physical means of maneuvering the memory-shaped
alloy
cuff and graft segment during the in-vivo penetration of an unobstructed blood
vessel; (b) to offer means for maintaining the engaged cuff and graft segment
combination in a desired position on the obturator in-vivo; (c) to provide
tangible
means for exerting and expansion force to the interior surfaces of the
combined
alloy cuff and engaged graft segment if and when required in order to smooth
internal surfaces and/or remove internal twists which might otherwise occur
during
the surgical procedure itself; and (d) to provide a hemostasis tool by
plugging the
arterial puncture hole in case of failure in the placement of the cuff which
would
result in potential bleeding.
IV. T6e Bypass Graft Material
Two major sources of conduits suitable for use as a bypass graft are
presently known and available. These are: synthetic prosthetic channel
sections
and previously excised blood vessel segments.
The choice of graft conduit it crucial to the success of coronary artery
bypass grafting surgery (CABG) because the patency of a coronary conduit is
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closely associated with an uneventful postoperative course and a better long-
term
patient survival. The standard vascular conduits used for CABG are excised
blood
vessel segments taken from the greater saphenous vein (GSA) or another leg or
arm vein. An excellent substitute conduit for coronary bypass operations that
can
be available on demand is certainly the desire of every practicing cardiac
surgeon.
However, virtually every synthetic alternative to arterial conduits or
autologous
fresh saphenous vein conduits has proved disappointing. Fortunately, patients
with
absolutely no autologous conduit are uncommon. Circumstances exist, however,
that often necessitate the use of alternative synthetic conduits such as young
10' hyperlipemic patients; as absent or unsuitable autologous internal mammary
artery
and greater saphenous vein as a result of previous myocardial
revascularization,
peripheral arterial reconstruction; and varicose vein ligation procedures. In
the
present era of increasing numbers of repeat coronary revascularizations,
approximately 15 % of patients requiring CABG are now in need of alternative
synthetic conduits.
A. Synthetic Conduits
The desired characteristics of synthetic conduits used as bypass grafts are
nonimmunogenicity, easy availability and storage, less risk of kinking (due to
its
stiffness), a less turbulent flow (due to uniform diameter), and an absence of
branches.
The medical value of synthetic conduits as bypass grafts in-vivo has been
substantially investigated. See for example: Foster ~~1., Circulation 79 S( up
1):
134-139 (1989); and Canver, C.C., C est 108: 1150-1155 {1995); and the other
references cited below. A summary review of the recent reports evaluating
these
conduits thus is in order.
Historically, Sauvage and associates in 1976 ~ Th rac. Cardiovasc. Sure.
72; 418-421 (1976)] described the placement of a 4:0-cm long, 3.5-mm diameter
knitted Dacron flamentous vascular prosthesis as an interposition graft
between the
aorta and right coronary artery during repair of a vascular aneurysm of the
ascending aorta in an adult. The graft was demonstrated to be patent by
angiography 16 months after operation. A literature search at the time found
only
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two other prior reports of successful aortocoronary grafting with synthetic
conduits,
both involving children with congenital coronary defects. Two factors present
in all
three cases that were suggested as promoting long-term patency were that only
short segments of prosthetic graft were placed, and that they were implanted
as
interposition grafts from the end of the coronary artery to the aorta.
The initial results of CABG with expanded polytetrafluoroethylene (PTFE)
(Gore-Tex. W.L. Gore and Associates, Elkton, Maryland) grafts were
encouraging; however, this impression was based on single-case reports or
series
with small numbers of patients. Molins and co-authors in 1978 [~ Thorac.
C~rdiovasc. ur 7~: 769-771 (1978)] presented a patient in whom they had
constructed a bypass to the distal right coronary artery with a 4.0 mm
diameter
PTFE graft; found patent on catheterixation 3 months after surgery: Also,
Yokoyama and associates in 1978 ~ Th_, orac. Cardiovasc. ur 7ø: 552-555
(1978}] described five aortocoronary bypass patients in whom 3.0-5.0-mm PTFE
grafts had been used. Four of five of these grafts were open on restudy 3-6
months postoperatively. Subsequently, Islam and colleagues in 1981 Ann
Thorac. Surg. 31: 569-573 (1981)] reported that a 6-mm diameter PTFE graft
used
for aorta-to-right coronary artery bypass remained widely patent on repeat
angiography 18 months after surgery.
An indication of the early and midterm results of CABG with PTFE grafts
was provided in the 1981 report of Sapsford and associates [J. Thorac."
~ardiovasc.
Surgs $1_: 860-864 (1981)]. Twenty-seven coronary bypasses were constructed in
16 patients with 4.0-mm P1'FE grafts. Eleven patients were restudied at 3
months
after surgery, and a 61 % (11 of 18) graft potency rate was found, in six
patients
rvho had repeat angiography 12-29 months after CABG, six of nine PTFE grafts
were open. Then, Murta and co-authors in 1985 Ann. Thorac. S_ur~. ~9: 86-87
(1985)] detailed a single case experience where two 4.0-mm diameter PTFE
aortocoronary grafts remained present 53 months postoperatively. More
recently,
Chard and associates reported in 1987 ~J r c. Cardiovasc. Surs. 94: 132-134
( 1987)] long-term potency results with PTFE aortocoronary grafts. Using both
one-to-side and multiple, sequential, side-to-side anastomoses, they
constructed a
total of 28 distal coronary grafts in eight patients. Potency rates on repeat
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angiography were 64 % ( 18 of 28) at 1 year, 32 % (9 of 28) at 2 years, 2 Z %
(6 of
28) at 3 years, and 14% (4 of 28) at 45 months.
The choices of materials recognized as being suitable for the making of a
biocompatible synthetic conduit are quite limited. These are provided by Table
4
below.
B. The Excised Blood Vessel Segment
A variety of blood vessel segments excised from the vascular system in-vivo
are suitable for use as bypass graft conduits. A representative, but
incomplete,
listing is provided by Table 5 below.
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Table 4: Synthetic Conduit Materials
Synthetic Substances
Dacron (knitted or woven) polymer;
Polytetrafluoroethylene or "PTFE" (knitted or woven);
Impra;
Teflon polymer;
Kevlar polymer;
Polycarbonated urethan;
Silicone;
Thermoplastic polymers and elastomers; and
Collagen, human or bovine.
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Table S: Vascular Conduits For Bypass Grafting
Venous Conduits
(a). Autologous vein conduits.
Greater saphenous vein segments;
Lesser saphenous vein segments;
Upper extremity (cephalic and basilic) vein segments.
(b). Nonautoiogous vein conducts.
Umbilical vein segments;
Greater saphenous vein homografts.
Arterial Conduits
(a). Autologous arterial conduits.
Internal mammary artery segments;
IS Right gastroepiploic artery segments;
Inferior epigastric artery segments;
Radial artery segments;
Splenic artery segments;
Gastroduodenal artery segments;
Left gastric artery segments;
Intercostal artery segments.
{b). Nonautologous arterial conduits.
Bovine internal thoracic artery segments.
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The preferred sources of blood vessels suitable for use as a vascular bypass
graft are the saphenous veins. These veins constitute the superficial veins of
the
lower extremities and comprise both the greater (or long) saphenous and the
lesser
(or short) saphenous veins. Anatomically, the long saphenous vein begins on
the
medial side of the foot and ends in the fermoral vein below the inguinal
ligaments;
and the short saphenous vein begins behind the lateral malleous and runs up
the
back of the leg to end in the popliteal vein. However, if the saphenous veins
of the
particular patient are unsuitable or unavailable for any reason, either the
cephalic
or the basilic veins are very acceptable substitutes for use as a vascular
bypass
conduit. However, if these leg or arm veins are not available, synthetic or
other
biologic materials may also be used as substitutes.
The medical procedure to isolate and excise the saphenous vein of choice is
conventionally known and considered a routine surgical technique. The
saphenous
vein is harvested under general anesthesia. An incision is first made in the
medial
malleolus, where the saphenous vein is often dilated. The saphenous vein is
identified and then dissected with a single incision made along its course
with
scissors. Branches are doubly clamped with hemostatic clips and divided. The
saphenous vein is then freed up and removed from the leg. The leg wound is
closed with subcutaneous sutures and Steristrip adhesive over the incision.
The
vascular segment is prepared on a separate sterile table with adequate light
and
loupes, and branches are selectively ligated with 4-0 silk. An oval-tip needle
on a
syringe is inserted into the graft to gently dilate it by administering a
balanced
electrolyte solution (pH 7.4, chilled to 7° to 10°C) and 10,000
unitslliter of
heparin. A valvulotome is inserted into the vein graft segment and the valves
25, clipped with a 3-mm right-angle stainless steel instrument with a highly
polished
ball tip on the right angle. The knife edge is protected and sharply splits
the cusp,
causing valvular incompetence. Measurements for the approximate lengths of the
grafts may be made with umbilical tapes, and the appropriate lengths may be
chosen before it is sewn to the cuff and coronary arteries.
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V. The Introduces System
The introduces system comprises the catheter apparatus including the
thermoelastic deformable cuff and a bypass conduit in combination; and it is
this
introduces system which is utilized by the surgeon to perform the requisite
acts and
S manipulations by which the bypass conduit is delivered to and becomes
secured
within the lumen of the unobstructed major blood vessel {and subsequently
anastomosed to the obstructed blood vessel at a site distal to the
obstruction). For
descriptive purposes and for increased clarity of camprehension, this
description
will intentionally Iimit itself to the use of the variable-sized obturatar
illustrated by
Figs. 9 and 10 respectively; to the thermally deformable cuff structure
illustrated
previously by Figs. 23A, 23B and 23C respectively; and to the use of a
previously
excised vascular segment taken from the long or short saphenous vein in the
same
patient. The introduces system represents and provides for the intentional
placement and carriage of the bypass conduit on the obturator, the engagement
and
j uncture of the deformable cuff to one end of the bypass conduit prior to
grafting'
in-vivo; and the proper orientation of the then engaged cuff/bypass conduit
together
on the obturator with respect to its relationship to the puncturing headpiece.
The preferred introduces system begins with the proper placement of a
previously excised vascular segment (desirably taken from the saphenous vein)
upon the obturatar and inflatable on-demand balloon. This initial manipulation
is
illustrated by Fig. 42 in which a previously excised vascular segment 460
having
two open ends 464 and 466 is placed upon the elongated shaft 134 over the
inflatable balloon 420 and adjacent to but preferably not in direct contact
with the
base plate I26 of the puncturing headpiece 122 of the obturator (previously
shown
by Figs. 9 and 10 respectively). As shown by Fig 42, it is intended and
preferred
that the elongated shaft 134 be inserted at the proximal end 138 into the
internal
lumen 462 of the excised vascular segment 460 by the surgeon; and that the
body
of the vascular segment 400 then be conveyed over the axial length of the
elongated shaft 134 until the open end 464 and vascular portion 470 are at a
chosen
position, typically 1-2 centimeters from the distal end adjacent to the
puncturing
headpiece 122. In this mariner, the weight and body of the excised vascular
segment 460 is carried on the elongated shaft 134; and it is desirable that
the
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diameter of the elongated shaft 134 be smaller than the overall diameter of
the
internal lumen 462 for the vascular segment 460. As a consequence of this
placement, the excised vascular segment is adequately supported, carried, and
transported by the elongated shaft during the entirety of the manipulations
prior to
entry into the body of the living patient as well as subsequent to the in-vivo
perforation of the unobstructed major artery or vein. The manipulation
illustrated
by Fig. 42 is expected to be performed by the surgeon immediately after
excising
the vascular segment from the patient but prior to beginning the bypass graft
surgery itself.
After the excised vascular segment 460 has been properly positioned on the
elongated shaft 134 over the balloon 420 of the obturator 120, the deformable
cuff
300 (illustrated by Fig. 23 and described in detail previously herein) is
desirably
passed over the puncturing headpiece 122 and over the open end 464 to cover
the
small portion 470 of the exterior surface over of the excised vascular segment
460.
This is illustrated by Fig. 42. It is desirable (but not absolutely necessary)
that a
gap distance "g" (about 1-2 centimeters) separating the open end 464 from the
puncturing headpiece 122 be maintained during the placement of the deformable
cuff over the inflatable balloon 420 -- as this will allow for easier
positioning of
the thermally deformable cuff in a pre-chosen aiignment and posture and in a
more
controlled manner of deformation on-demand.
When the deformable cuff 300 has been positioned over the balloon 420 and
the vascular segment to the satisfaction of the surgeon, the lower sidewall
portion
312 of the cuff covering the exterior surface 470 nearest the open end 464 of
the
excised vascular segment 460 must be physically engaged and become joined to
the
vascular segment in a reliable and safe manner. This is illustrated by Fig.
43.
One preferred manner of engagement and juncture is for the surgeon to suture
the
open meshwork of the cuff 300 directly to the portion 470 of the excised
segment
460. This suturing is easily performed by the surgeon prior to beginning the
grafting surgery and each of the sutures 480 will serve as the physical means
for
engaging and permanently joining a portion of the open meshwork of wires in
the
sidewall of the cuff to the excised vascular segment itself. The type of
sutures
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480, their placement, their number, and the linkage to the vascular wall of
the
excised segment are left to the personal discretion and choice of the surgeon.
Other means for permanent engagement and juncture of the thermally
deformable cuff to the vascular wall of the excised segment also are commonly
available. These include surgical staples; biocompatible adhesives; encircling
ligatures; and a wide range of surgical fasteners and closures. Any and all of
these
alternatives may be employed alone or in combination to achieve a reliable
engagement and juncture.
One optional variation of the introduces system provides that the open
IO- meshwork sidewall 306 of the cuff 300 can be covered with synthetic
materials to
facilitate the suturing, stapling or other means for attaching the prosthetic
channel
section or vascular segment to the cuff. These biocompatible synthetic
materials
can be applied in one or more layers or coatings to the cuff; and serve as an
overlay for a portion or the entirety of the cuff sidewall.
In addition, another optional variation of the introduces system allows the
sidewall of the cuff to be positioned within the lumen of the prosthetic
channel
section or excised vascular segment. In these instances, the meshwork sidewall
of
the cuff is incorporated within the interior of the prosthetic conduit or
vascular
bypass segment in order to eliminate the need for direct sewing of the bypass
conduit to the cuff. This variant thus offers a simplified procedure for
locking the
cuff to the bypass conduit in a permanent fashion.
After the deformable cuff 300 has been engaged and joined to one end of
the excised vascular segment 400 then carried upon the balloon 420 on the
elongated shaft 134 of the obturator, the size of the puncturing headpiece 122
should be adjusted in shape and girth such that the diameter of the base plate
124
of the puncturing headpiece 122 preferably is equal to or slightly smaller
than the
diameter of the open cuff end 302. This manipulation is also illustrated by
Fig. 43
where the size of the base plate 12b is coextensive in diameter with the
diameter of
the open end 302 of the deformable cuff. In this preferred manner, the
entirety of
the puncturing headpiece I22 serves as a front section or first stage for the
introduces system as a whole.
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The complete introduces system is illustrated by Fig. 44 in which the fully
prepared obturator carrying the previously excised vascular segment to be used
as a
bypass conduit and the thermally deformable cuff have been positioned in
advance;
and the prepared obturator with positioned inflatable balloon has been placed
within
the internal lumen of a catheter. As seen therein, an introduces catheter 80
as
shown in Fig. 8 previously, appears in an exposed, cross-sectional view and
shows
the hollow tube 82 of fixed axial length having a discrete proximal end 94, a
discrete distal end 88 and an internal Iumen 86 of pre-determined diameter
sufficient to house the entirety of the prepared obturator (illustrated by
Fig. 43).
The distal end tip 90 and central distal portal 92 of the catheter is adapted
for
direct delivery.of the introduces catheter in-vivo to a chosen site where an
unobstructed artery or vein is in anatomic proximity to an obstruction lying
within
another blood vessel; and the prepared obturator of Fig. 43 (comprising the
previously excised blood vessel segment and the deformable cuff) lies within
the
internal lumen 86 of the introduces catheter. The introduces system shown by
Fig:
44 is complete; and the surgeon may now begin the first steps for surgically
delivering the introduces system into the thoracic cavity or other appropriate
body
region in order to create the bypass graft.
Maintaining the ambient temperature of lh~,internal lumen of the catheter at
less
than ~~out 25-3S°~
The preferred means for cooling and maintaining the temperature of the
internal lumen in a guiding catheter comprising the introduces system at less
than
about 2S-35°C during the creation of a bypass graft in-vivo is via the
use of cold
25_ physiological-strength (0.85-0.9 % ) saline. Typically, a sterile saline
pack is
refrigerated in advance of the repair surgery and cooled to a temperature
between
40-SO°F (5-10°C). The cooled saline is then infused by the
surgeon into the
internal lumen of the catheter in order to cool the thermally deformable cuff
both
initially and periodically during the surgery. The sterile saline is
compatible with
the living tissue of the patient; and multiple applications of saline can be
introduced
into the internal lumen volume of the catheter as often as deemed necessary
without meaningful risk to either the introduces system or the patient.
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As an alternative to the use of saline infusion, any other suitable means for
cooling (such as gaseous carbon dioxide) may also be employed as a less
preferred
practice for maintaining he environmental temperature of the internal lumen
volume of a catheter at less than about 2S-35°C: Such alternative
procedures,
however, are often less desirable due to the effects of potential direct
contact and
possible biological reaction when intentionally or inadvertently released into
the
bloodstream or other highly vulnerable organs and tissues of the body.
Nevertheless, the use of alternative means to reduce the environmental
temperature
of the internal lumen~volume of a catheter to less than about 25-35°C
can be safely
and properly performed in many different medical circumstances using the
present
invention.
VI. The Routing And Surgical Introduction
Of The Controlling Catheter
into The Body Of The Living Human
Catheterization involves a great deal of technical skill, some instrumentation
and mature judgment in order to choose among the appropriate procedures and
the
various techniques which are now conventionally known and available for use.
Clearly, because the present technique constitutes catheter intervention in
critically
ill patients, the physician or surgeon must be very familiar with the
available
anatomical alternatives in order to select the best routing for introducing
the
catheter, the best technique in order to access the thoracic cavity of the
body where
the obstructed artery and aorta exist, and. to carefully select the timing and
other
operative conditions in order to achieve best results.
In general, catheterization can be performed using any duct, tube, channel,
or passageway occurring naturally or surgically created for the specific
purpose.
Thus, among the naturally occurring passageways in the body are the anus; the
alimentary canal; the mouth, ear, nose, or throat; a bronchus of the lung; the
urethra; the vaginal canal and/or cervix; and any blood vessel of sufficient
size of
the central circulation in the body. Any of these routings are envisioned and
expected to be used when and if appropriate. However, clearly a commonly used
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and the critical route of access is the introduction of catheters into the
thoracic
cavity and the arterial blood circulation adjacent to the heart.
For this reason, it is useful to briefly summarize the technique currently in
use for introduction of catheters into the central bioad circulation as an
illustrative
example of preferred catheterization techniques. There are three general
methods
currently in use. These are: (a) percutaneous introduction using needles and
guidewires followed by introduces sheath placement; (b) direct introduction
after
surgical isolation of the blood vessel of choice; and (c) direct trocar
puncture
technique. While any general method may be utilized at any site of the general
circulation, practical and anatomical considerations will generally dictate
which
approach is most appropriate under the individual circumstances.
The modified Seldinger Technique:
The percutaneous introduction of a catheter is illustrated by the modified
Seldinger technique which is shown by Figs. 45A-45F respectively. Fig: 45A
shows a blood vessel being punctured with a small gauge needle. Once vigorous
blood return occurs, a flexible guidewire is placed into the blood vessel via
the
needle as shown by Fig. 45B. The needle is then removed from the blood vessel,
the guidewire is left in place, and the hole in the skin around the guidewire
is
enlarged with a scalpel as shown by Fig. 4SC. Subsequently, a sheath and a
dilator is placed over the guidewire as shown by Fig: 4SD. Thereafter, the
sheath
and dilator is advanced over the guidewire and directly into the blood vessel
as
shown by Fig. 45E. Finally, the dilator and guidewire is removed while the
sheath
remains in the blood vessel as illustrated by Fig. 45F. The catheter is then
inserted through the sheath and fed through to reach the desired location.
The other general method for the introduction of catheters into the blood
circulation is a direct surgical cutdown. Cutdown procedure is often a complex
invasive surgery and is used only no direct access is generally available. A
far
more complete and fully descriptive review of both these general
catheterization
techniques is provided by the texts of: Diagnostic And Therapeutic Cardiac
Catheterization, second edition; 1994, Chapter 8, pages 90-110 and the
references
cited therein.
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Accordingly, for purposes of practicing the present methodology, any and
all conventionally known general catheterization procedures and techniques
which
are conventionally known and in accordance with good medical practice are
explicitly intended to be utilized as necessary in their original format or in
a
modified form. All of these general catheterization routing and use techniques
are
thus envisioned and are deemed to be within the scope of the present
invention.
General rules for choosing. ~ appropriate site of bod3r en,~:
An axiomatic or general set of rules by which a surgeon or radiologist can
chose a proper or appropriate site of entry for introducing the guiding
catheter into
the body of a patient for purposes of creating a vascular bypass in-vivo is as
follows: (a) always pick the shortest and straightest pathway possible or
available;
{b) identify the chosen entry site on an existing and accessible unobstructed
artery
or vein, the larger the diameter of the unobstructed artery or vein the
better; and
(c) identify the location and orientation of the obstruction in the obstructed
artery
or vein and chose an entry site distal to the obstruction.
A favored ap~ro"~ch to introducing_the guiding_catheter into the thoracic
aorta:
Using the ascending aorta approach as a representative illustration and
example:
(I) Under general anesthesia, the chest of the patient is prepared and
draped in a sterile fashion.
(2) A three-inch incision is made to the Ieft or right of the breast bone
through which the surgeon operates.
25. (3) Three additional one-inch incisions then are made to insert a video
camera, knife, surgical stapler, and other instaruments.
(4) The ribs are separated, the thoracic cavity is entered, and the
ascending thoracic aorta is exposed.
(5) The introducer system is then positioned at the chosen site on the
ascending thoracic aorta.
(6) The penetration can be monitored by an ultrasound apparatus placed
in the esophagus.
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VI. The In-Vivo Placement Of The Vascular Bypass Graft
Luto The Lumen Of The Unobstructed Major Blood Vessel
The method of the present invention utilizes the introduces system via the
catheterization technique to create a bypass graft conduit between a major
unobstructed blood vessel such as the aorta and an obstructed blood vessel in-
vivo
using a previously excised vascular segment as a conduit. This procedure is
illustrated by Figs. 46-54 collectively. It will be recognized and
appreciated,
however, that while Figs. 46-54 exemplify and illustrate the manipulations of
the
surgeon and the events in sequence leading to the creation of a vascular
bypass,
this description and the figures themselves present a greatly simplified
presentation
and explanation of the medical procedure, the technical skills required, and
the
safety measures taken for the patient's benefit medically. The use of
synthetic
conduits and fixed-size obturators, although not described; is also within the
scope
of the present methodology:
After the introduces system catheter has been routed and surgically
delivered into the body of the living human in the manner described previously
herein, the first stage for the process is reached as shown by Fig. 46. The
illustration of Fig. 46. (as well as Figs. 4?-54 respectively) are shown as
partially
exposed views in order to show more easily the detailed placement and
orientation
of the introduces system comprising an obturatar with positioned balloon
carrying
the improved deformable cuff and previously excised vascular segment in
combination.
As seen within Fig. 46, a major artery such as the aorta 500 is shown in
25_ partial cross-sectional exposed view to reveal the thickness of the
arterial wall 502
and the internal lumen 504. The catheter and the prepared obturator comprising
the introduces system are as described in detail previously herein and
illustrated by
Fig. 43. It will be noted that the puncturing headpiece 122 of the obturator
120 is
positioned within the lumen of the catheter such that the perforating end tip
130 is
in direct contact with the arterial wall 502 at the chosen anatomic site. The
puncturing headpiece 122 is of sufficient size such that the entirety of the
thermally
deformable cuff 300 and the joined vascular segment 460 lie directly behind
and
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are in axial aiigriment with the puncturing headpiece 122 and the elongated
shaft
134: When positioned as shown by Fig. 46, the prepared obturator has been
cooled to a temperature less than about 25°C (using cold saline or
gaseous carbon
dioxide), and is properly placed for piercing and penetrating the arterial
wall on-
demand.
then the surgeon extends the prepared obturator within the cooled and
temperature controlled internal lumen of the catheter, the result is
illustrated by
Fig. 47. As seen therein, the perforating end tip 130 has punctured and
pierced
through the arterial wall 502; and been advanced into the arterial lumen 504.
The
initial pierced hole in the arterial wall 502 made by the perforating end tip
130 is
widened into a passageway as a consequence of the entire puncturing headpiece
122 following the entry path created by the perforating end tip. As the
puncturing
headpiece 122 penetrates through the arterial wall 502, the size of the
puncture in
the arterial wall becomes widened and enlarged to conform to and accommodate
the configuration and the girth of the puncturing headpiece in its entirety.
The
configuration and overall size of the puncturing headpiece 122 thus serves as
the
means for enlarging the initial puncture made by the perforating end tip 130
such
that the entire girth and overall diameter of the obturatar (complete with
thermally
deformable cuff and excised blood vessel segment in combination) can
subsequently
pass through the enlarged hole in the arterial wall.
As the prepared obturator is extended further across the thickness of the
arterial wall 502 through the enlarged passage, the penetrating headpiece I22
is
desirably extended farther into the arterial lumen 504 until at least the
upper
sidewall portion 308 of the thermally deformable cuff 300 also has been
advanced
25. far enough to lie within the internal lumen of the blood vessel. This
sequence of
events and result is illustrated by Fig. 48. The balloon 421 is also inflated
at this
stage of events to hold the cuff 300 and engaged graft segment 460 in
position.
Then the surgeon slowly and carefully withdraws the catheter 82 from the
passageway in the arterial wall 502 while maintaining the inflated balloon
421, the
cuff 300 and graft 460 of the prepared obturator in a stationary position.
Consequently, the upper sidewall portion 308 of the cuff 300 is slowly
released
into the arterial lumen 504 from the internal lumen 86 of the receding
catheter 82
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and the upper sidewall 308 of the thermoelastic alloy cuff begins to deform in-
situ
into its second memory-shaped configuration. This manipulation and result is
illustrated by Fig. 49.
As seen therein, the surgeon has activated the means for contracting the
girth of the puncturing headpiece; and partially withdrawn the catheter such
that
the uppermost part alone of the cuff has been released into the warm
temperature
environment of the arterial lumen in-vivo. Thus Fig. 49 shows the partial and
sequential beginning of thermal deformation for the cuff in-situ within the
arterial
lumen.
Fig. 49 also shows that the puncturing headpiece 122 has been reduced in
overall size and shows a diminished diameter or girth in comparison to its
initial
size as shown previously via Figs. 42-43 respectively. The reduced overall
size
and altered configuration of the puncturing headpiece 122 lying disposed
within the
arterial lumen in-vivo is a preferred manipulation of the methodology provided
by
the use of variable-size obturators.
Alternatively, the puncturing headpiece 122 may be fixed in both size and
shape; and the thermally deforming sidewall of the cuff 300 will be made to
expand outwardly along its length in order to allow the fixed-size puncturing
headpiece to pass through the outwardly expanded cuff diameter. Also, the
outward expansion by the deformed cuff can improve and enhance watertightness
between the cuff 300 and the arterial wall 502.
After the puncturing headpiece has been desirably reduced in overall size
and has a diminished girth, the overall diameter of the contracted puncturing
headpiece 122 is smaller in overall size than the diameter of the partially
deformed
25. cuff disposed directly behind the headpiece. Due to the reduced size of
the
puncturing headpiece 122, the partially deformed cuff and engaged vascular
segment carried upon the elongated shaft 134 of the obturator may later be
withdrawn from the distal end 88 of the catheter.
It is important to recognize and note that a meaningful portion of the upper
sidewall of the thermoelastic cuff 300 has been released out of the catheter
lumen
into the arterial lumen 504 as illustrated by Fig. 50. Concomitant with the
controlled release of the thermoelastic cuff 300 into the arterial lumen 504,
two
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consequential events also occur: (a) the engaged and joined vascular segment
460 is
concurrently placed and fitted into the enlarged puncture or hole in the
arterial wall
502 at the chosen site; and (b) the upper sidewall portion 308 of the cuff, as
it is
freed from the confinement of the internal lumen of the catheter and placed in
a
warm temperature environment above 35°C, begins to deform thermally
into the
memory-shaped second configuration.
The degree of extension and rate at which the.engaged cuff and the vascular
segment is controllably released from the catheter lumen lies at the
discretion of
the surgeon performing this methodology. If the surgeon so chooses, the
deformable cuff and the excised vascular segment may be extended through the
thickness of the arterial wall but not far or completely into the arterial
lumen itself.
In the alternative, the surgeon may choose to advance the engaged cuff and
vascular segment extensively or completely and thus position the upper
sidewall
portion of the cuff as far as possible within the internal lumen of the artery
itself.
i5 The degree of entry as well as the rate of release of the deformable cuff
and the
engaged vascular segment into the warm temperature environment above
35°C of
the arterial lumen thus is the choice and judgment of the surgeon at ali
times. It
can be monitored and also guided by a transesphogeal ultrasound, which is
commonly used during current cardiac surgeries.
After the thermoelastic cuff 300 and the engaged vascular segment 460 have
been advanced such that each has penetrated the arterial wall 502 and at least
a
portion of the upper sidewall 308 of the deformable cuff 300 has been released
into
the arterial lumen, to the surgeon's personal discretion and accommodation,
the
uppermost region 308 of the deformable cuff 30(? will thermally deform in-situ
into
25, the memory-shaped second configuration -- as shown by Fig. 50. The warm
temperature environment above 35°C of the arterial lumen has caused the
upper
sidewail 308 of the cuff to deform in-situ; to become bent outwardly; and to
become Haired and flattened out within the internal lumen 504 of the artery
500.
Then, as the memory-shaped second configuration for the cuff appears in an
ever
greater degree, the sidewall 308 of the cuff 300 will become more flattened;
will
come to lie substantially against the interior surface of the arterial wall
502; and
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will become secured to the arterial wall in a permanent manner. This
consequence
and result is also illustrated by Fig. 50.
The controlled thermal deformation and flairing of the lowermost sidewall
312 of the cuff 300 then occurs in-situ; and the act of controlled deformation
is
continued as shown by Fig. 51 without substantially diminishing the rate of
blood
through the Iumen of the artery or causing the heart of the patient to stop at
any
time. Merely by continuing to withdraw the catheter 82, the intentional and
controlled thermal deformation of the cuff along its lower sidewall 312 occurs
as it
lies disposed against the exterior surface of the artery 500. This causes a
permanent flairing of the open meshwork of wires forming the lower sidewall
312.
The deformed sidewall 312 becomes bent, maneuvered, and flaired in-situ into
its
memory-shaped configuration merely by warming the cuff to a temperature above
35°C. No tool, article, or mechanical device is needed or utilized in
order to
cause a controlled deformation of the cuff while disposed within the blood
channel
of the artery in-vivo. The results is shown by Fig. 51.
After the cuff has been thermally deformed within the arterial lumen 504
and subsequently become secured to the exterior surface of the artery 500 to
the
personal satisfaction of the surgeon, the balloon 420 is intentionally
deflated and
the puncturing headpiece 122 and the obturator as a whole can be removed. The
surgeon is confident that the overall diameter of the contracted puncturing
headpiece and the deflated balloon are smaller than the diameter of both the
cuff
and the engaged vascular segment; and therefore, the puncturing headpiece will
then be able to enter and pass completely through the fully deformed cuff and
the
internal lumen of the engaged vascular segment in-situ without meaningfully
injuring or altering the internal surface of the blood flow channel itself.
The act of removing the obturator is quickly accomplished by the skilled
surgeon; and the act of removal shown by Fig. 52 serves to isolate the now
fully
deformed sidewalls 308 and 312 of the cuff 300 secured to the interior surface
and
to the exterior surface of the arterial wall 502. The completely deformed cuff
300
and the engaged vascular segment 460 remain permanently secured and attached
to
bath the interior and the exterior of the major artery in a manner which
permits
arterial blood to enter through the deformed cuff into the internal lumen of
the
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. vascular segment without meaningful major alteration of the primary artery
and
without major destruction of vascular tissues at the site of graft bypass
juncture.
To ensure that the placement of the deformed cuff and engaged vascular segment
is
fluid-tight, the surgeon then preferably applies a biocompatible adhesive 530
to the
exterior surface of the arterial wall 502 at the puncture site. The
biocompatible
adhesive 530 is desirably spread over the sidewall 312 of the cuff 300 at the
exterior surface of the arterial puncture site. Some surgeons might place some
sutures between the outer flare of the cuff and the exterior wall of the aorta
instead
of or before placement of an adhesive. This act and result is shown by Fig.
53.
The applied biocompatible adhesive dries quickly; forms a permanent and fluid-
tight seal at the puncture site; and will not degrade or cause irritation to
either the
artery wall or the grafted vascular segment now to be used as a bypass
conduit.
Note also that the catheter has desirably been removed prior to the placement
of
the biocompatible adhesive at the puncture site on the arterial wall and the
cuff.
This catheter removal step is preferred in order to have better access to the
thermally deformed cuff at the point of juncture.
A number of different biocampatible adhesives may be employed to seal
permanently the puncture site in the manner shown by Fig. S3. A representative
but non-exhaustive listing of such biocompatible adhesives is provided by
Table 6
below.
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Table 6: Biocompatible Adhesives
Adhesives Materials
Fibrin glue;
Histacryl (butyl-2-cyanoacrylate) tissue adhesive;
Cyanoacrylates;
Liquid silicones;
Epoxy resins;
Polyurethane adhesives; and
Derma Bond (Closure Medical Corp:).
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The overall result of this procedure is illustrated by Fig. 53 in which the
uppermost region 308 of the cuff sidewall has been thermally deformed in-situ
and
become flaired outwardly, into the internal lumen 504 while the lowermost
portion
312 has been thermally deformed onto the exterior surface of the artery 500.
The
open meshwork of wires has aided and assisted the ease and speed by which the
deformed sidewalls 308 and 312 have bent, become extended and become secured
in-situ to the interior and exterior surfaces concurrently of the arterial
wall 502.
Also, the placement of the biocompatible adhesive 530 at the puncture and
graft
j uncture site places the bypass conduit in a fluid-tight setting permanently
such that
the engaged vascular segment 460 is attached to and is in blood flow
communication with the arterial blood in an unobstructed manner. The placement
and securing of the vascular bypass conduit to the major unobstructed artery
is thus
complete in all respects.
The other end of the excised vascular segment 400 typically is then
conventionally attached to the obstructed blood vessel at a chosen site distal
to the
obstruction itself as illustrated by Fig. 54. The manner of joining the second
open
end of the grafted vascular segment to the obstructed artery or vein may be
achieved conventionally by anastomosis; with or without sutures; and with or
without use of tissue adhesives by the surgeon. It will be noted and
appreciated
also, that the surgeon, at his option, may in fact intentionally create an
aperture in
the wall of the grafted vascular segment; introduce the obturator into the
internal
lumen of the vascular segment; place a second deformable cuff in proper
position;
and then engage the cuff to the second open end of the vascular segment in the
manner described previously. If the surgeon so chooses, therefore, the
entirety of
the introducer system and the cauterization methodology may be repeated for
use at
the chosen site on the obstructed blood vessel. Nevertheless, it is generally
expected that in most instances, the surgeon will prefer to perform
conventional
anastomosis as the means for joining the other open end of the blood vessel
segment to the obstructed artery or vein. This is illustrated by Fig. 54.
The entire catheterization methodology for creating a vascular bypass graft
or shunt has been shown and described in detail via Figs. 4b-54 inclusive.
Each
essential manipulation or required act has been illustrated in detail and
described in
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depth. Nevertheless, to assure a complete and comprehensive presentation of
the
methodology as a whole, a summary recitation of the preferred surgical
procedures
using the catheter apparatus, the introduces system, and the methodology is
provided hereinafter.
VI. SUMMARY OF THE PREFERRED SURGICAL
PROCEDURES USING THE CATHETER APPARATUS
AND METHOD
The catheter apparatus and methodology comprising the present invention
provides an approach designed to allow surgeons do multiple bypass using vein
bypass grafts in a minimally invasive way. This procedure allows a simpler way
to place the vein grafts proximally to the aorta and distally to the coronary
artery
without using a heart-lung machine and without need for stopping the heart.
Small
incisions are first made between the ribs; a video camera and instruments with
long
handles are inserted; and, under the direct visualization, the aorta is
punctured to
create a proximal graft to anastomosis (aortotomy) using a specially prepared
catheter introduces system which internally carries a deformable cuff and a
previously excised vascular segment.
The thermally deformable cuff is made of nickel-titanium alloy wire mesh
with or without a coating of prosthetic material such as PTFE. The cuff will
become anchored by thermal deformation at a temperature above about
35°G to
both the interior and exterior of the aortic wall and be secured and blood-
leak-
proven outside the aortic wall by subsequently applying a tissue adhesive.
This
thermally deformed cuff will provide a secure sutureless aortic anastomosis
for the
bypass vein graft. The proximal part of the vein graft is preferably sewn to
the
cuff. The bypass graft is then distally anastomosed to the coronary artery,
which
can be done either by the conventional way with sutures or by applying tissue
adhesive between the adjacent outer walls of the bypassable coronary artery
and the
bypass vein graft without sutures.
This unique procedure simplifies the complexity of the conventional
coronary artery bypass surgery and makes the surgery less invasive. Moreover,
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this technique provides a critical advantage over the conventional bypass
surgery
(using excised vein grafts), or the thoracoscopic minimally invasive surgery
(using
an internal mammary vein graft). Also, it will shorten the operation time and
make the coronary bypass surgery safer and more cost-effective.
Thoracotom~,and AorotocorQnary Bv~
After cutting through the muscle and other tissue of the anterior chest, the
surgeon separates a rib from the breast bone and cuts a piece of the cartilage
at the
detached end to provide working space for the aortotomy and placement of the
proximal graft anastomosis.
The bypassing of the vascular blockage increases blood flow to the heart.
The optimal environment for the vascular anastomosis is a motionless, dry
field.
In conventional coronary bypass surgery, this environment can be obtained by
total
cardiopulmonary bypass and cardioplegia techniques to arrest the heart.
However,
in minimally invasive coronary bypass surgery, it is performed without
cardiopulmonary bypass and without stopping the heart. Instead, the heart beat
is
slowed down with cardiac medications such as calcium channel Mockers and beta-
blockers, and with hypothermia.
Creation of the eroximal anastomosis
The ascending aorta is first palpated and examined by transesophogeai
ultrasound before creation of the aortotomy to determine the proper location
of the
aorta for aortotomy and delivery of the introducer system. The ascending aorta
is
preoperatively evaluated by means of CT scan or MRI to exclude the patient
with
severe atherosclerosis of the aorta, which may interfere with creation of the
aorotomy and increase possible associated complications such as dissection and
embolization of the plaques. When the ascending aorta is shown to be
moderately
thick by CT or MRI, the deformable cuff is larger (7 to 10 mm outer diameter)
than usual (2 to b mm outer diameter) and may be placed in the aorta to
prevent
narrowing at the proximal anastomosis.
This technique involves safe and simple placement of the proximal
anastomosis of the vein graft without clamping of the aorta and without using
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heart-lung machine. The proximal part of the ascending thoracic aorta is first
exposed and punctured with an obturator that carries a cuff and a previously
excised blood vessel segment within it. The cuff is made of a nitinol wire
mesh;
and will thermally deform into a memory-shaped flared end which will become
firmly anchored against the inner wall and the exterior surface of the
thoracic
aorta. The cuff is desirably covered with a prosthetic material (such as
Dacron
and PTFE; etc.) to prevent any leaking of blood through the mesh cuff although
vascular grafts can be sewn directly to the cuff. Continuous 5-0 to 7-0
Prolene is
used for the anastomosis between the cuff and the grafts when the saphenous
vein
is the usual size (5 to 6 mm).
After the aortic puncture, the proximal end of the cuff vein graft is
partially
thermally deformed as it is released into the arterial lumen. The catheter is
then
slowly retracted and the vein graft is slowly pulled back until the lower
sidewall of
the cuff is anchored and secured against the exterior wall of the aorta via
its
deformed lowermost end. Once the cuff and the proximal end of the vein graft
is
internally and externally anchored, the catheter and obturator are removed;
tissue
adhesive (glue) is applied around the exit site of the bypass graft {between
the graft
and the adjacent outer wall of the aorta) so that any possibility of leakage
of blood
will be minimized and also to secure further the proximal anastomosis although
sutures can be placed between the cuff and the exterior wall of the aorta. The
upper end of the vein graft is clamped to stop blood flow; and drugs are
injected
into the lower end to prevent it from going into spasm while the surgeon works
on
the coronary anastomosis.
Exposure of the ~oronar~arteries and creation of the
distal anastomosis
The sac covering the heart is cut, the thin coronary artery is under direct
view. The patient is given calcium channel blockers and a beta blocker
intravenously to slow the heart, which facilitate that the surgeons thread the
stitches
through the artery. The coronary artery vessels to be bypassed is identified
and
exposed after opening either hemithorax.
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With a sharp knife, the surgeons cut into the coronary artery (arteriotomy).
The arteriotomy is then increased to 8 to 12 mm with Pott's or reversed acute
angle scissors. The internal diameter of the coronary artery is calibrated and
the
size recorded. The distal part of the graft that has been set aside is sewn to
the
coronary artery with the same fine sutures that are used in standard bypass
operations. A continuous suture of 6-0 or 7-0 Prolene is begun in the heel of
the
vein graft with a narrow mattress stitch and continued to the proximal portion
of
the coronary artery. Approximately 1-mm bites are taken as the suture line is
continued around one side to the distal end. At that point the suture line may
be
interrupted with one or more sutures. With smaller vessels interrupted sutures
are
easy to insert and less likely to constrict the anastomosis. With larger
vessels (2.5
mm or greater) the suture line may be continued without interruption around
the
distal end. The other end of the original stitch is continued on the
contralateral
side, and the anastomosis is terminated at the midpoint of the arteriotomy.
Anastomotic potency is checked in both directions. A flush of clear solution
through the needle may be of aid during the performance of the distal
anastomosis
to keep the anastomotic area free of blood. Alternatively, the coronary artery
and
bypass vein grafts can be anastomosed by applying tissue adhesive (glue)
between
their adjacent outer walls, or by laser welding, or by using staplers, all
without
using sutures, which facilitates and expedites the coronary anastomosis. when
application of tissue adhesive make two structures bonded in a side-to-side
fashion,
a fenestration in a proper length is made between them by putting an incision
extending from the lumen of vein graft to the lumen of the coronary artery
with a
knife inserted via the distal open end of the graft. After this, the open
distal end
of the vein graft is sewn as a blind end.
This procedure is repeated until all the blocked vessels to be revascularized
are bypassed. After checking for bleeding, the surgeon closes the chest.
The present invention is not to be limited in scope nor restricted in form
except by the claims appended hereto.
