Note: Descriptions are shown in the official language in which they were submitted.
GUID~D ATEEREC~OMY SYSTEM
CROSS REFERENCE TO OTHER APPLICATIONS
This application is a continuation in part (CIP) of application
SN 07/350,020 filed 5/12/89 which is a CIP of four applications: application
SN 07/326,967 filed 3/22/1989, application SN 07/324,616 filed 3/16/1989,
application SN 07/323,328 filed 3/13/1989, and application SN 07/332,497 filed
3/13/1989. These four applications are CIPs of application SN 07/286,509
filed 12/19/1988 (now patent number 4,894,051) which i5 a CIP of application
SN 07/243,900 filed 9/13/1988 (now patent number 4,886,490), which is a CIP of
I _ three applications, application SN 07/078,042 filed 7/27/1987 (now patent
number 4,819,634), application SN 07/205,479 filed 6/13/1988 (now patent
number 4,883,458), and application SN 07/225,880 filed 7/29/1988 (now patent
number 4,842,579). These three applications are CIPs of application SN
07/018,083 filed 2/24/1987, which is a CIP of application SN 06/874,546 filed
6/16/1986 (now patent 4,732,154) which is a CIP of application SN 06/609,846
filed 5/14/1984 (abandoned).
All the above applications are being incorporated herein by reference.
BACKGROUND AND OBJECTIVES OF THE INVENTION
With age a large percentage of the population develops atherosclerotic
2 arterial obstructions resulting in diminished blood circulation. The
disturbance to blood flow that these obstructions cause may induce blood clots
which further diminish or block the blood flow. When this process occurs in
the coronary arteries it is referred to as a heart attack. Presently such
obstructions are circumvented by surgically grafting a bypass or they are
treated by angioplasty which tends to in~ure the arterial wall, create a rough
lumen and in substantial number of cases is ineffective. Further, angioplasty
does not remove the obstruction material out of the arterial system, therefore
in a case of a heart attack, immediate angioplasty carries the risk of
dislodging the blood clot and allowing it to move down stream creating
Page 2
additional blockages. ~ ~ ~
An objective of the present invention is to provide an atherecto~y system
having a flexible guide wire with a casing which positively guides a flexible
catheter to and through an obstruction. The flexible guide wire defines a
void or voids in which the obstruction material is positively held during the
coring process. The process does not crack the vessel's wall and yields an
enlarged smooth lumen.
Preferably, the system could be made in large and in small diameters,
down to approximately lmm (millimeter) and a length of approximately a meter,
1 to reach and enter small and remote arteries. The system's operation willpreferably utilize the physician's existing skills such as: gaining access to
the vessel, guide wire placement through the obstruction, angiographic
evaluation of the obstruction, etc.
The above and other objectives of the invention will become apparent fro~
the following discussion and the accompanying drawings.
BRIEF DESCRIPTION OF THE FIGURES
FIGURE 1 generally shows an atherectomy system inserted at the groin area
through the arterial system of a patient, into his obstructed coronary artery.
FIGURE 2 shows a cross sectioned view of an atherectomy system with a
2 flexible guide wire made of a flexible casing in the form of a helical wire
attached to a proximal extension tube and a flexible pilot wire incorporating
an ultrasound pod. The middle portion of the atherectomy system is removed
due to space limitations on the drawing sheet.
FIGURE 3 shows a distal end portion of a flexible guide wire with an
ultrasound pod having teeth on its distal end.
FIGURE 4 shows a distal end portion of a flexible pilot wire with a
similar pod to the one shown in FIGURE 3, disposed in a deflecting sleeve.
FIGUR~ 5 shows the trajectory of the system in a cross sectioned, curved
obstructed artery, when the coring process is done over a flexible guide wire
3 having a casing over which the flexible catheter is accurately guided.
FIGURE 5' shows two optional blade configurations.
Page 3
FIGURE 6 shows the possible range of trajectories of the system in a
cross sectioned, curved obstructed artery, when the coring process is done
over a standard flexible guide wire.
FIGURES 7 and 7' shows an enlarged, partially sectioned view of the
distal end section of a helical wire where the distal entry to the void
defined between the coils is partially closed by a short tube.
FIGURES 8 and 8' show end views of the helical wire shown in FIGURE 7 and
7', respectively.
FIGURE g shows an enlarged, partially sectioned view of the distal end
l section of a helical wire where the distal entry to the helical void defined
between the coils is partially closed by a tube sectionO
FIGURE 10 shows an end view of the helical wire shown in FIGURE 9.
FIGURE 11 shows an enlarged, sectioned view of the distal end section of
a helical wire made of two flat layers, where the distal entry to the helical
void defined between the coils is partially closed by a short tube.
FIGURE 12 shows an end view of the helical wire shown in FIGURE 11.
FIGURE 13 shows a further enlargement of the cross section of the helical
wire of FIGURE 12.
FIGURE 14 shows the flexible guide wire used in the embodiment of FIGURE
2 16 withbarrier means in their contracted position.
FIGURE 15 shows a cross sectioned view of the flexible guide wire shown
in FIGURE 14 along a line 15-15 marked on FIGURE 14.
FIGURE 16 shows a cross sectioned view of the distal end portion of an
atherectomy system with a coring means in the form of a tubular-blade
utilizing auxiliary energy, disposed over a flexible guide wire having
expanded barrier means.
FIGURE 17 shows a cross sectioned view of the system shown in FIGURE 16
along a line 17-17 marked on FIGURE 16.
FIGURE 18 shows a cross sectioned view of an atherectomy system where the
3 coring means utilizes a radiation emitting device (the flexible guide wire is
omitted).
FIGURE 19 shows a distal end view of the system shown in FIGURE 18.
FIGURE 20 shows a psrtially cross sectioned view of an inflatable chamber
Page 4
~o~
located at the distal end of the flexible sleeve.
FIGURE 21 shows a cross sectioned view of the system shown in ~IGURE 20,
along a line 21-21 marked on FIGURE 20.
FIGURE 22 shows a partially cross sectioned view of an atherectomy system
with a flexible sleeve having a selectively actuatable tongue at its distal
end,
FIGURE 23 shows a partially cross sectioned view of the system shown in
FIGURE 22 along the line 23-23 marked on FIGURE 22.
DETAILED DESCRIPTION OF THE DRAWINGS
I FIGURE 1 generally shows an atherectomy system 10 inserted at the groin
area through the skin, through a patient's arterial system, into a coronary
vessel 13 serving the patient's heart 11.
FIGURE 2 shows the atherectomy system 10 (similar parts will be indicated
by same numbers throughout the FIGURES) for removing an obstruction 12 from
within the patient's vessel 13. ~The atherectomy system comprises several
elongated parts in a nested relationship, and their ends shall be referred to
as "distal" meaning the end which goes into the vessel and "proximal" meaning
the other end. Thus, "distal direction" or "distally" shall indicate a
general direction from the proximal end to the distal end, and "proximal
2 direction" or "proximally" shall refer to an opposite direction.
The atherectomy system comprises:
A flexible guide wire 140 insertable into the vessel.
A flexible catheter 21 slidable over the flexible guide wire, having a
coring means in the form of a tubular blade 22 at its distal end, defining a
continuous passage 25 around the flexible guide wire for ingesting the cored
obstruction material.
The flexible guide wire is made of a thin walled stainless steel
extension tube 17 sr lt can be made similarly to the catheters shown in my
above mentioned patent 4,819,634. The extension tube 17 is attached to an
3 _ ~ auger shaped helical wire 170 which is slidably guided over the flexible pilot
wire 160. Silicon oil or other blo-compatible lubricants may be disposed in
Page 5
the extension tube to ease the motion of the flexible pilot wire thereinS
while preventing blood from clotting inside the extension tube and interfering
with this motion. A helical void is defined between the coils of the wire 170
for holding the obstruction material.
A nipple 14 is connected to the proximal end of the extension tube 17
through an annular chamber 15 which slidingly seals around the flexible pilot
wire.
The flexible guide wire's section which extends distally into the vessel
from the flexible catheter concentrically aligns the flexible catheter with
1 the vessel and provides a lever arm which angularly aligns the flexible
catheter with the vessel (also note FIGURE 5).
When the flexible catheter's distal end 23 bears against the vessel's
wall, it does so through a relatively large contact area, spreading the
contact force and minimizing any trauma to the vessel.
The atherectomy system uses "mechanical energy" to advance and rotate the
tubular blade and additional "auxiliary energy", emitted by the distal end
portion of the atherectomy system, to soften a boundary lsyer of the
obstruction material and ease in the coring process. The auxiliary energy can
be in the form of, for example, heat, laser or ultrasound energy. Some of the
2 auxiliary energy can be retrieved by a suitable transducer and processed toimage the obstruction site in order to make the coring process safer and to
assess the results of the proc~dure.
Coring the obstruction material is more efficient than pulverizing all of
the obstruction material. To illustrate this point, when a tubular blade
having a wall thickness of .25mm cores an obstruction with an outside diameter
of 5mm and sn inside diameter (lumen) of lmm the area of the boundary layer
that the tubular blade has to pulverize is only a fifth of the obstruction's
a~ea and correspondingly one fifth of the volume.
Suction can be applied to the flexible catheter through a port 33 which
3 communicates with a groove 34 defined by a motor's housing 28', which
communicates with hole 39, which communicates with a hollow shaft 29, which
communicates with the proximal end of the continuous passage 25. Preferably
the suction is proYided by a positive displacement pump 33' such as a piston
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20~ ~S77
pump or a peristalic pump which tends to self regulate the evacuation process:
it limits the amount of blood removed through the flexible catheter to the
volume that is positively displaced by the pump, when only free flowing blood
is present in the continuous passage the negative pressure in the continuous
passage automatically drops, as obstruction material enters the cont$nuous
passage the negative pressure automatically rises and pulls the cut material
proximally. A feedback control 19 can be used to decrease the pumping rate of
pwmp 33', through wiring 24 in response to sensing through a tube 20 that the
negative pressure between the pump and the catheter is below a certain level.
I Preferably, the suction is synchronized with the coring action, or it is
otherwise selectively controlled. These controls are designed to reduce the
amount of blood removed from the patient during the procedure. The maximum
level of negative pressure can be limited to prevent collapsing of the vessel
wall. Coupling means at the proximal end of the flexible catheter in the form
of a conical seat 27 couples it to a drive means in the form of a motor 28
having the hollow shaft 29 with a matching tapered end 31 and a seal 32 at its
other end. The hollow shaft and seal are slidingly disposed around the
flexible guide wire.
A pod 161 is used to emit auxiliary energy, which is sent by the base
? unit 162 through the flexible pilot wire, to the surrounding tissue, to soften
the surrounding obstruction material, and to optionally retrieve signals in
the form of returned auxiliary energy which is sent back to the base unit to
be processed to form an image of the obstruction site. Laser energy ean be
used to obtain a topographical image and ultrasound energy to obtain a
geological image. Relying on this information the physician can advance the
pilot wire with a reduced risk of perforating the vessel's wall.
The helical wire 170 takes up the free play between the flexible pilot
wire 160 and the flexible catheter 21 thereby concntrically aligning one with
the other. A void defined between the helical wire's coils serves as a
3 barrier, holding the obstruction material during the atherectomy and
restraining the cored material from freely rotating around the flexible guide-
wire, and to the extent that the obstruction material i8 rotated by the
flexible catheter this rotation is translated by the helical wire to urge the
Page 7
5~
cored obstruction material proximally in the continuous passage. The helical
wire can be inserted into a tight obstructlon by rotating it, threading it
into the obstruction. In the process of threading, the helical wire pulls
itself across the obstruction and anchors itself in the obstruction material.
When the flexible catheter is pushed forward in the vessel, the flexible guide
wire can be pulled to offset the longitudinal force in the atherectomy system
which tends to buckle the flexible catheter.
A flexible sleeve 71 in which the flexible catheter is disposed isolates
the vessel's wall from the flexible catheter, and can be used to introduce the
I flexible catheter into the vessel and direct it to the obstruction's si~e.
A nipple 72 is connected to the flexible sleeve through an annular chamber 73
equipped with a seal 74 which seals around the flexible catheter and
communicates fluid entering the nipple 72 to move in the sleeve around the
flexible catheter into the vessel.
FIGURE 3 shows a second embodiment of a pod 163 having protrusions 164 on
its distal end for drilling and a mid section 165 for emitting and receiving
auxiliary energy. The protrusions allow a physician to use the pod as a drill
by rotating the pilot wire, enabling him to safely cross hard obstructions
while knowing the pod's relative location to the vessel's wall. The
2 protrusions may range in size from discrete teeth as shown in FIGURES 3 and 4
to microscopic protrusions which may be formed by bondin~ diamond particles to
the pod's distsl end. Auxiliary energy could be used ~o assist the pod in
penetrating through the obstruction, with or without rotation thereof. The
auxiliary energy which is emitted by the pod is transmitted to the adjacent
obstruction material which eases the threading of the helical wire through the
obstruction.
FIGURE 4 shows a distal portion of a flexible pilot wire 160 disposed in
a deflecting sleeve 82' having an inflatable chamber 81', for deflecting the
trajectory of the flexible pilot wire in the vessel. The deflecting sleeve
3_ 82' and inflatable chamber 81' is a scaled down version of a deflecting sleeve
82 and an inflatable chamber 81 shown in FIGURES 20 and 21 and performs in the
same manner. The deflecting sleeve can be si2ed to guide the pilot wire or to
guide the whole flexible guide wire through the vessel.
Page 8
2()~ 7~
FIGURE 5 shows the trajectory of an atherectomy system in a cross
sectioned, curved obstructed vessel, when the coring process is done over a
hollow flexible pilot wire 14 and a casing made of a helical wire 170 attached
by a brazing 49 to an extension tube 17. An optional inflatable chamber 15 is
attached to the pilot wire and can be inflated or deflated through the hollow
flexible pilot wire 14 which communicates fluid from its proximal end to an
orifice 68. The inflatable chamber can be used to center the flexible pilot
wire in the vessel, to cushion the contact between the flexible pilot wire and
the vessel's wall as well as for anchoring it to the vessel's wall. If the
I inflatable chamber is asymmetric it can also be used to selectively bias the
position of the flexible pilot wire in the vessel.
FIGURE 5' shows two optional blade configurations that will be discussed
later on.
FIGURE 6 shows the range of possible trajectories of the system in a
cross sectioned, curved obstructed vessel, when the coring process is done
directly over a standard flexible guide wire 35.
FIGURE 7 shows an enlarged, partially sectioned view of the distal end
section of a casing in the form of a helical wire 18 where the distal entry to
the void defined between the coils is partially closed by a thin gate in the
2 form of a short tube 19, preferably made from radio opaque material (for
example an alloy comprising gold and/or platinum), attached to the internal
diameter of the casing. The helical wire is made of a tube with a lumen 41
through which auxiliary energy can be conveyed and emitted at the distal end
of the helical wire to ease its threading into the obstruction material~ ~
FIGURE 8 shows a distal end view of the casing shown in FIGURE 7 in the
form of a helical wire 18 having a pointed distal end 40 to ease penetration
into the obstruction material.
~IGURE 7' shows an enlarged, partially sectioned view of the distal end
section of a casing in the form of a helical wire 18' where the distal entry
3 to the void defined between the coils is partially closed by a thin gate in
the form of a short tube 19', preferably made from radio opaque material,
attached to the outside diameter of the casing.
FIGURE 8' shows a distal end view of the casing shown in FIGURE 7' in the
Page 9
7~
form of a helical wire 18' having a pointed distal end 401 to cut and ease
penetration into the obstruction material.
FIGURE 9 shows an enlarged, partially sectioned view of the distal end
section of a casing in the form of a helical wire 26 where the distal entry to
the void defined between the coils is partially closed by a thin gate ln the
form of a tube section 30, preferably made from radio opaque material,
attached between the coils of the helical wire, adjacent to the internal
diameter of the casing.
FIGURE lO shows a distal end view of the casing shown in FIGURE 9 in the
l form of a helical wire 26 having a pointed distal end 42 to ease penetration
of the obstruction material. As the helical wire 26 is rotated and advanced
around a flexible pilot wire the point 42 remains adjacent to the flexible
pilot wire. If the flexible pilot wire is disposed against the arterial wall,
as the helical wire is advanced and rotated, its inclined leading edge gently
separates the arterial wall from the flexible pilot wire and centers it in the
vessel. Option2lly the point 42 can be moved away from the flexible pilot
wire, as shown in FIGURE 8, which makes the pointed helical wire thread more
aggressively through the obstructlon ~aterial while reducing its ability to
separate the arterial wall from the flexible pilot wire as discussed above.
2 ~ FIGURE ll shows an enlarged, sectioned view of the distal end section of
a casing in the form of a helical wire 93 made of two flat layers
64 and 66, where the distal entry tu the void defined between the coils is
partially closed by a thin gate in the form of a short tube l9 attached to the
internal diameter of the casing. The multi layer construction decreases the
cross section modulus of the helical wire around a neutral axis 69 which is
perpendicular to the main axis 70, as compared with a non-layered
construction, but it has minimal effect on the cross section modulus around à
neutral axis 84 which is parallel to the main axis 70.
FIGURE 12 shows a distal end view of the casing shown in FIGURE ll in the
i form of 8 helical wire having a pointed distal end 62 for the purpose
discussed aboYe in conjunction with FIGU~E lO.
FIGURE 13 shows a further enlargement of the cross section of the helical
wire of FIGURE 12. The layers 64 and 66 are encapsulated in a plastic
Page 10
2~ 7
material 85 which holds them together and makes them thread through the
obstruction material in unlson, but is sufficiently flexible to allow their
cross section modulus to be that of two separate layers. Auxiliary energy
conduits 65 and 67, are also encapsulated by the plastic material along side
the layers of the wire. Preferably, the plastic material has a slippery outer
surface to ease its insertion through the vessel and its threading through the
obstruction material.
FIGURE 14 shows a flexible guide wire 87 having a hollow pilot wire 90
and a casing in the form of thin jacket 88 with arrays of slits 89 which
I define collapsible and expandable ribs 61. The jacket is slidable over theflexible pilot wire 90, up to an enlarged rounded distal end 91. Under the
compressive force which is generated by pushing the proximal end of the jacket
while pulling the proximal end of the flexible pilot wire, the ribs fold and
expand to form barriers 56, as shown in FIGURES 16 and 17, and at this
position they define a void (the term "void" as used in conjunction to this
application shall mean the gaps defined between barriers 56, collectively, or
it may refer to a single continuous gap, as in previous embodiments) which
holds the surrounding obstruction material and counters its distal movement
during the atherectomy. The diameter of the expanded top barrier element 56'
2 can be made larger than the inner diameter of the flexible catheter to block a
larger cross sectional area of the vessel, whereas the other barrier elements
are made to fit inside the flexible catheter which they slidably support.
The hollow pilot wire 90 can be used as a conduit for delivering fluids
to the obstruction site and beyond, such as: radio opaque fluid to assist in
fluoroscopic imaging of the vessel, oxygen rich fluid for providing
nourishment to deprived cells during the procedure, or fluid for irrigating
the work site.
FIGURE 15 shows a cross sectioned view of the flexible guide wire shown
in FIGURE 14.
3 FIGURE 16 shows a distal end portion of an atherectomy system having a
coring means in the form of a tubular blade 44. The tubular blade has teeth
86 and a ring shaped element 45 in the blade, to which auxiliary energy is
conveyed by means of two flexible conduits 46 and 47 located in a wall of a
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S77
flexible catheter 48. The tubular blade emits suxiliary energy to the
surrounding obstruction material. The emitted energy may have several forms
which assist the blade in corlng the obstruction material. If the auxiliary
energy is thermal the ring can be a resistive element to which the conduits
carry electrical current or the ring can be made to absorb laser energy and
then the conduits would be fiberoptic bundles. Optionally, the tubular blade
can be made from semi-transparent or transparent material, and part or all of
the laser energy can be transmitted directly to the obstruction material. If
the emitted energy is ultrasound energy the ring can be a piezoelectric
_I_ transducer to which the conduits carry electrical current.
The auxiliary energy delivered to the tubula} blade eases the coring
process by softening the boundary layer, and since the obstruction material is
positively held in the void defined by the flexible guide wire 87 it may be
possible to core the obstruction by pushing the catheter without rotating it,
especially if there is an anatomical reason not to impart torque onto the
vessel for example, when working in a graft that is poorly attached to the
surrounding tissue~ However, coring by rotation is preferable because it is
more effective and the relative rotational motion between the vessel and the
flexible catheter which entails overcoming the frictional force between them,
2 eases the advancement of the flexible catheter in the vessel. The relative
rotational motion between the flexible catheter to the obstruction material,
which also entails overcoming the frictional force between them, eases the
proximal movement of the obstruction material in the flexible catheter
(because overcoming the frictional forces between two bodies, due to a
relative motion between them in one direction, minimizes the frictional
resistance to a relative motion between them in a perpendicular direction).
FIGURE 17 shows a partially cross sectioned view of the system shown in
FIGURE 16.
FIGURE 18 shows a flexible catheter 51 with a coring means utilizing
3 _ auxiliarg energy, preferably in the form of laser energy carried by optical
fibers 52 and emitted through their distal ends. The auxiliary energy cores
the obstruction by ablating a narrow boundary layer in it and the continuous
passage 63 ingests the cored obstruction material as in previous embodiments.
Page 12
577
Similarly to the tubular-blade, the laser based coring means is efficient and
uses less energy in comparison to other laser based systems which ablate all
the material of the obstruction,
Optionally, the emitted laser energy can be directed in a slightly
outwardly inclined direction as shown in FIGURE 18, so that a wider boundary
layer of material would be ablated to make the diameter 94 of the recanalized
vessel larger than the diameter 95 of the flexible catheter 51 and larger than
the puncture wound that is needed to introduce the flexible catheter into the
vessel, while the center part of the obstruction can still be cored
unpulverized.
The flexible catheter 51 can be disposed in any of the sleeves shown in
connection to the embodiments of the present invention. By using a sleeve
equipped with a toroidal chamber to block blood flow as explained above and by
introducing fluid to the obstruction site, for example saline solution,
through the sleeve or the flexible catheter, a working medium of choice can be
created to suite a specific type of radiation and to allow visual or
spectroscopic analysis of the vessel's lumen.
As previously discussed, the auxiliary energy may enable the physician to
core the obstruction material by pushing the flexible catheter with or without
2 rotating it.
FIGURE 19 shows a distal end view of the flexible catheter shown in
FIGURE 18 together with the flexible guide wire 87.
FIGURES 20 and 21 show a biasing means in the form of an asymmetrical
inflatable chamber 81 formed at the distal end of a flexible deflecting sleeve
82 which, when inflated, through a channel 83 formed in the sleeve's wall,
bears against the vessel's wall, as shown in solid lines, eccentrically
biasing the flexible sleeve and the coring means towards an eccentric
obstruction 195. When deflated, as shown by phantom lines, the chamber
conforms to the sleeve to minimize interference with its insertion into the
3 vessel. Alternatively the chamber can be shaped as an asymmetrical toroidal
inflatable c~ ~ ber 81' as shown in FIGURE 21 by interrupted lines. This
chamber, when inflated, establishes peripheral contact with the vessel's wall
and thereby blocks blood flow between the sleeve and the vessel's wall, as
Page 13
20~577
well as eccentrically biasing the sleeve (it can be understood that a
symmetrical toroidal chamber can be provided ~or the purpose of blocking the
flow around the sleeve while centering the biasing sleeve). Any of the above
mentioned chambers can also be inserted into the lumen that has been cored by
the coring means, to be inflated therein with sufficient pressure, and to
further widen the lumen, however, such a procedure may introduce the drawbacks
of angioplasty.
FIGURES 22 and 23 show an atherectomy system where a flexible sleeve 76
has a tongue 77 which can be used when coring an eccentric obstruction 195.
I In such a case the tongue can be inserted opposite of the obstruc~ion to
protect the vessel wall and bias the trajectory of the coring means into the
obstruction. The tongue can be energized against the vessel's wall by
tensioning a flexible rope 79, moving the tongue from its relaxed position
which is shown by a phantoln line in FIGURE 22 and marked 77' to the position
shown in solid lines and marked 77.
OPERATION
FIGURE 5 illustrates the atherectomy process, First a portion of the
flexible pilot wire 14 is inserted into the curved vessel, and assumes the
. vessel's geometry. Then the casing in the form of the helical wire 170 is
2 _ inserted over the flexible pilot wire, preferably by threading it through the
obstruction. The flexible pilot wire acts as a lever arm 3 to angularly align
and safely guide the advancing helical wire 170 through the curved vessel.
Without the lever arm's guidance the advancing helical wire would contact the
vessel's wall at approximately a point 1 and exert a large concentrated
compressive force until the bending moment which equals the product of that
force multiplied by the short lever arm 2 would be sufficient to bend the
helical wire around an axis 5 perpendicular to the plane of curYature of 'he
vessel (and therefor shown perpendicular to the drawing sheet by a checkered
circle). In comparison, with the ~lexible pilot wire's longer lever arm.3 the
3 required force is smaller and it i8 spread by the lever arm over a longer and
larger contact area of the vessel's wall.
Page 14
---- 20~;S77
Once the helical wire is in place it reinforces the obstruction material
and firmly holds it in place, preparatory to coring it. At this point the
physician has an opportunity to, fluoroscopically or by the use of auxiliary
energy imaging, assess the position of the flexible guide wire in the vessel.
The flexible guide wire's portion that has been inserted through the
obstruction material now serves to concentrically align the flexible catheter
with the vessel and also serves as a lever arm which angularly aligns the
flexible catheter with the vessel during the atherectomy, The angular
alignment of the flexible catheter by the flexible guide wire is very similar
I to the alignment of the helical wire over the flexible pilot wire; the
flexible catheter is inserted over the flexible guide wire which acts as a
lever arm 4 to angularly align and safely guide the advancing flexible
catheter. Without the lev~r arm's guidance the advancing coring means would
contact the vessel's wall at approxi~ately a point 1 and exert a large
concentrated compressive force untll the bending moment which equals the
product of that force multiplied by the short lever arm 2 would be sufficient
to bend the flexible catheter around the axis 5, however such a compresslve
force will likely cause the coring means to cut and perforate the vessel. In
comparison, with the flexible guide wire's longer lever arm the required force
2 is smaller and it is spread by the lever arm over a longer and larger area of
-
the vessel's wall. Phantom lines mark the anticipated trajectory of the
coring means when it is accurately guided in the vessel as discussed.
FIGURE 5' shows two optional blade configurations. The right hand
configuration shows a blade 21' where the diameter of the sharp edge is on
internal diameter of the blade and is connected by a taper to the external
diameter. The taper acts to distance the sharp edge from the arterial wall
making it a safer configuratlon preferred for working in a torturous vessel.
If the blade is smooth the taper does not pulverize the boundary layer but
tends to push it outwardly.
3 _ The left hand configuration 22" shows a blade where the diameter of the
sharp edge is on the outside diameter of the blade and an inverted taper
connects it to the internal diameter. If the blade is smooth the inverted
taper does not pulverize the boundar~ layer but tends to push it inwardly and
Page 15
2~ 77
core it, however, with this configuration there is a higher probability of
injuring the arterial wall. Alternatively, the sharp edge can be formed
between the internal and outside diameters, as shown in FI W RES 5 and 6, to
combine in part the characteristics of both blade configurations.
FIGURE 6 illustrates the potential risk of guiding the coring process
over a standard flexible guide wire directly. As the tubular blade advances
along the flexible guide-wire its trajectory can vary angularly and sideways
in the range defined between the two phantom lines, and any material disposed
between the phantom lines, including large segments of the vessel's wall,
might be cored.
The process for removing an obstruction from a vessel with an atherectomy
system comprises the following steps:
a. Insert~ng into a vessel, into an obstruction, a flexible pilot wire. The
flexible pilot wire can be constructed like a standard flexible guide wire, or
it can be equipped with various means to assist the physician in inserting it
and guiding it through the arterial system and the obstructlon.
b. Inserting into a vessel, into an obstruction, over the flexible pilot-wire
a flexible casing having a void for holding the Gbstruction material (the
flexible pilot wire and casing can be pre-assembled before insertion or
permanently affixed one to the other, in which case the insertion of the
..
flexible guide wire assembly into the vessel is done in a single step which
replaces the above two steps).
c. Advancing over the casing a coring means located at a distal end of a
flexible catheter, coring and ingesting the obstruction material which is held
in place by the void. Concentric and angular alignment is provided by the
r flexible guide wire to the advancing coring means
d. Suction, which is preferably provided by a positive displacement pump
means, may be used to assist the cored obstruction material to move proximally
~ in the flexible catheter.
s 3 The sequence of inserting the system1s components into the vessel may be
!
varied. Steps may be combined or added to streamline or improve the process,
respectively, and in order to customize the procedure to the individual
characteristics of the obstruction and its location and to the working
;
Page 16
i,
preferences of the medical staff. For example, the system may be introduced
percutaneously (that is through the skin) or intra-operatively (that is when
the vessel is surgically exposed for accessing vessel), a standard guiding
catheter, which is either straight or pre-formed or has a selectively
controlled curve, may be used as a sleeve and inserted into the vessel to
assist in positioning the system's components in the obstruction site.
The preferred mode of operating an atherectomy system having an auger
shaped flexible guide wire is to first thread the flexible guide wire by
rotating it in one direction and advancing it across the obstruction, like a
I screw in a cork, and then hold the flexible guide wire in place while
advancing and rotating the flexible catheter in an opposite direction, over
the stationary flexible guide wire. It is also possible to continue and
rotate the flexible guide wire to increase the auger's proximal conveyance
action, especially when coring an obstruction with a slurry like consistency
such as fresh blood clots.
An atherectomy system can be manufactured in different diameters and
lengths depending on the size and site of vessel that it is intended for and
on whether the system is to be used percutaneously or intra-operatively.
It can be noted from the FIGURES that the basic components of the
2 atherectomy system can have several optional features and design variations.
ThP flexible catheter can be made from plastic or metal or from a combination
thereof and the coring means can utilize mechanical energy and/or auxiliary
energy. The flexible guide wire can be equipped with various types of casing
designs, some of which are affixed to the pilot wire and others that are
slidable thereon. The sleeve can be equipped with mechanical or hydraulic
biasing means. By combining a flexible catheter with certain features, a
flexible guide wire with certain features and a sleeve with certain added
features a variety of customized atherectomy systems can be made. This
increases the user's ability to match the system's characteristics with the
3 specific disease condition that is being treated, which is helpful, since the
clinical characteristics of arterial atherosclerotic obstructions vary in
their topography, geology and accessibility from one patient to another.
The aboYe and other modifications and substitutions can be made in the
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system and in its operation without departing from the spirit of the invention
or the scope of the following claims.
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