Note: Descriptions are shown in the official language in which they were submitted.
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aACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to wire guides having a Doppler
mechanism for determining ln vivo flow velocity of a biological
fluid. In particular, it relates to a flexible, steerable, fluid
velocity measuring wire guide which is receivable in a catheter
and positionable sub-selectively in the coronary arterial tree for
diagnosing heart disease.
2, Descri~tion of the Related Art
Coronary artery disease ls a common medical problem,
particularly in the United States, and often manifests itself as a
constriction or stenoses in the arterial tree. Coronary artery
disease can lead to increased arterial stenosis and gradual
diminution of reactive hyperaemic response. Because arterial
disease is commonplace, it is important to properly diagnose the
presence of specific lesions or vessel stenosis and to properly
evaluate the efficacy of treatment of these arterial lesions.
Stenoses past the coronary o~tlum are not only difficult to
ldentify and treat, but are also prime concern because of their
effect on available coronary vasodilator reserve. To identify
coronary disease, the arteriogram ha~ long been used to determine
the presence and extent of stenoses. Applicant's U.S. patent No.
4,~65,925 dlscusses the inadequacies of the arteriogram as an
ind~catlon of the presence and nature of coronary artery dixease.
See, White, et al., Interpretation of the Arterlocram, 310 New
Eng. J. Med. 819-824, (1g84).
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Transluminal angioplasty lenlargement of the lumen of
a stenotic vessel using an intravascular catheter) was
initiated by Dotter and Judkins in the mid-1960ls.
However, prior to the work of Gruentzig (mid-1970's),
coronary stenoses were usually treated by op~n heart
surgery, such as coronary artery bypass surgery.
Gruentzig developed an inflatable non-elastomeric balloon
mounted on a small catheter which could be introduced in~o
the vessel across the stenoses, and then inflated with a
sufficient force to enlarge the stenotic lumen. Since the
pioneering work of Gruentzig in the mid-1970's, there have
been significant improvements in the equipment and
techniques developed for this percutaneous transluminal
ccronary angioplasty (PTCA) procedure. In the United
States, the growth in the number of PTCA procedures being
performed has been dramatic - approximately 1,000 PTCA
procedures were performed in 1980 and over 100,000 proce-
dures were performed in 1986. PTCA procedures represent a
major alternative to bypass surgery and has en3oyed an
increasing success rate.
Although PTC~ procedures have become increasingly
success~ul, a major cause of failures is the inability to
accurately identify the regions of stenoses and to
evaluate the success of the angioplasty across the
stenotic vessel. That is, the arteriogram is still the
prime method of identifying and evaluating the stenosis
and can lead to any number of mistakes in interpretations
- such as observer error, superselective injection,
pulsatile injection of contrast media, total occlusion,
etc. ~urther, angiographic evaluation of the region of
stenoses after the PTCA procedure is often difficult,
owing to the poor definition of the vessel after angio-
plasty. Thus, while such cor~nary angioplasty techniques
have been relatively successful in treating the regions of
stenosis, the unreliability of the arteriogram has been a
significant detraction from the efficiency of angioplasty.
717
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Because a PTCA procedure uses a steer2~1e suidewi-e
to place the angioplasty balloo~ cathet^r subselectively
in the coronary vessels, it would be a signific~t advance
in the art and a major improvement over the arte-iogram if
a guidewire were devised which was capa~le of getting a
direct indication of blood flow in a particular region of
the coronary vessel. Further, it would be a significant
advance if such a guidewire capable of m~asuring fluid
velocity were devised which was useful in measuring
velocity of other biological flui~s and was easily
positioned in a biological vessel of interest.
SUMMARY OF THE INVENTIO~
The velocity determining wire guide of the present
invention provides one solution for subselectively
identifying the nature and extent of coronary artery
disease, and further provides a device which is useful in
invasively determining biological fluid flow in any small
or constricted vessel. Advantageously, the wire guide of
the present invention is of such a size (less than .030
inch) that it will easily fit d~wn the ceneral lumen or
side channel of an angioplasty catheter which itself is
such a size to be subselective in the coronary arterial
tree. Preferably, the wire guide hereof is steerable a~d
is useful not only as a probe for locating regions of
heart disease, but also as a guide for an angioplasty
catheter.
Broadly speaking, the wire guide of the present
invention includes an elongated member which is generally
longitudinally inelastic and flexible for threading
engagement with the catheter. A Doppler mechanism is
3~ coupled to the distal end of the elongated mem~er and is
operable for determining the velocity of the blood when
inserted in the arterial tree. Electrical lead means
coupled to the Doppler mechanism run along the member
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towards the proximal end of the guic~ wire, such tha.
blood velocity can be determi~ed as the wire guide is
selectively advanced in the arterial tree.
In a preferred form, the wire guide includes an
elongated support wire having a pair of electrical leads
running along the length thereof, with the leads and sup-
port wire encapsulated in an insulator sheath. A Doppler
crystal is connected to the leads and is secured to the
dis.al end of the sheath with the face of the Doppler
crystal generally perpendicular to the longitudinal axis
of the sheath. In an alternative embodiment, the distal
end of the wire guide is bent at a small angle, such that
torque control of the support wire reorients the distal
end carrying the Doppler crystal for selective steer-
ability and better Doppler signal reception.
In another preferred embodiment, the elongated member
comprises a helically wound spring coil defining a central
passageway therein. The Doppler crystal is fitted to the
distal end of the spring coil and electrical leads are
coupled to the Doppler crystal and received within the
central passageway. An elongated inelastic fixed core
wire is secured to the distal end and proximal end of the
spring coil to prevent longitudinal elon3ation of the
spring coil. In an alternative embodiment, the distal
portion Df the spring coil is in a ~J" shaped configura-
ti~n. Advantageously, a movable coil wire is shiftably
received in the central passageway and operable such that
when it is shifted into the region of the "J" shaped
configuration, the region tends to straighten out. Thus,
the movable core allows the Doppler crystal to be oriented
as desired and allows the distal end of the spring coil to
be directionally aligned for subselective movement in the
arterial tree.
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BRIEF DESCRIPTIOi~ OF THE D^~iING~
FIGURE 1 illustrates a fragmentary, side elevatior~l
view of a velocity measuring wire guide in accordance with
the present invention;
FIGURE 2 is an enlarged, fragmentary, sectional view
of a proximal portion of the wire guide illustrated in
FIGURE l;
FIG~RE 3 is an enlarged, fragmentary, sectional view
of the distal region of the wire guide of FIGUR_ l;
FIGURE 4 is a fragmentary, side elevational view of
an alternative embodiment of the dist~l region of the wire
guide of FIGURE l;
FIG~RE 5 is an enlarged, fragmentary, sectional view
of a wire guide in accordance with the present invention
which includes a coil spring in a "J" shaped configuration
and a movable core;
FIGURE 6 is an enlarged, fragmentary, sectional view
of a wire guide which includes a straight coil spring;
FIGURE 7 is an enlarged, fragmentary, sectional view
showing in detail the joinder of the Doppler crystal to
the coil spring; and
FIGURE 8 is an enlarged, fragmentary, sectional view
of a wire guide in accordance with the present invention
having a ~J" shaped distal region without a moveable core.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Turnin~ now to the drawings, a wire guide 10 in
accordance with the present inventi~n is illustrated in
l.'~'~t j71.7
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vari~us embodiments. Broadly speakir.~, the wir~ suide 10
incluàe~ an elongated, flexible, lonyitu~inally i~elastic
wire me~ber 12, Doppler mechanism 1~ and electrical leads
16 running the len~th of the member 12.
In more detail, in the embodimen~s depicted in
FIGURES 1-4 the wire member 12 inclu~es an elongated
supp~rt wire 20 which is flexible and longitudinally
inelastic, and torquable in the sense that a twisting
moment at the proximal end will impart a twisting moment
at the distal end. The s~pport wire 20 i5 preferably a
stainless steel piano wire and in the preferred
embodim~nt, has an approximate outer diameter of .012
inches. The electrical lead 16 comprises a pair of
electrical connector wires juxtaposed in adjoining
relationship to the support wire 20. The leads 16 have an
approximate outer diameter of .002 inches and preferably
include a copper conductor having four layers of a thin
nylon i~sulation. A cylindrical, insulator sheath 22 of
plastic, nylon, polyurethane, or other suitable insulating
- material envelopes the support wire 20 and electrical
leads 16, to present an outer diameter preferably less
than .030 inches, and in the pre~erred embodiment having
an outer diameter of .019 inches.
Turning to ~IGURE 2, the sheath 22 is received in an
insulating sleeve 24 substantially as shown. Doppler
connector cable 26 leads into the opposite end of the
sleeve 24 and is connected to the lead 16 by the coupling
wires 28 as shown. As illustrated in FIG~RE 1, the
connector cable 26 terminates in a universal coupling 3~.
As shown in detail in FIGURE 3, the Doppler mechanism
14 includes a generally flat Doppler crystal 32 which is
preferably a pizeoelectric ceramic crystal comprising a
lead-zircante-titanate material. The D~ppler crystal 32
is approximately .003 inch in thickness and is designed to
resonate at 20 megahertz. A pair of conductors
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(preferably gold) are attached to the crystal 32 such that the
Doppler crystal 32 operates as a pulsed Doppler, operating alter-
natively as a transmitter and receiver. The conductors 34 are
connected by the electromechanical joints to the leads 16. A
potting compound 36, such as an epoxy resin, secures the Doppler
crystal 32 in the circular opening defined by the sheath 22. As
can be seen in FIGURE 3, the distal end of the support wire 20
terminates prior to the distal end of the sheath 22, leaving a
void which is filled by the potting compound 36.
As can be appreciated by those skilled in the art,
Doppler mechanism 14 is connected through the universal coupling
30 to operate as an ultrasonic pulsed Doppler device capable of
measuring the velocity of a fluid. See e.g., C. Hartl~y and
J. Cole, Pulsed Doppler Flow Measurement, 37 J. App. Phys., 626-
629 (1974).
Comparing FIGURES 1 and 4, it is seen that FIGURE 4
presents a slightly different embodiment in which the distal region
of the wire guide 10 (FIGURB 4) is bent at a slight angle relative
to the remaining longitudinal alignment of the member 12. Thus,
the embodiment of FIGURES 1-3 presents a "straight" wire guide
while the FIGURE 4 embodiment has a "hockey stic~" orientation of
its distal region. In some applications, the FIGURE 4 embodiment
allows better steerability (tor~uing the member 12) to orient the
distal end towards the coronary vessel of interest.
Turning now to FIGURES 5-8, further embodiments of
the distal region of the wire guide 10 in accordance with the
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present invention are illustrated. In the FIGURE 5-8
embodiments, the member 12 comprises a helically wound spring
coil 40 having an annular cross section to define a central
passageway 42. The outer diameter of the spring coil 40
is preferably less than .030 inches and as illus-
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trated, is less than .019 inch, such that the wire suide
10 will easily fit in the lumen or coupling channel of a
dilation ca'heter or the like. An elongated fiYed core
wire 44 is coupled to the spring coil 40 at the distal and
proximal ends to prevent longitudinal elon~ation of the
spring coil 40 during manipulation. FIGURE 7 shows the
weld 46 securing the fixed core 44 to the last two winds
of the spring coil 40 at the distal end of the wire guide
10, it being understood that the fixed core 44 is similar
secured to the proximal end.
In the embodiments of FIGURES S and 8, the distal
region of the wire guide 10 is made to assume a "J" shaped
configuration in its normal static state. While an
introducer (not shown) is co~only used to straighten the
"J" shaped configuration during percutaneous insertion,
the embodiment of FIG~RE 5 additionally includes an
elongated movable core 48 shiftably received in the
central passageway 42. As those skilled in the art will
appreciate, the movable core 48 is usually not flexible
enough to conform to the "J" shaped configuration of the
central passageway 42. Rather, the movable core 48 as it
is advanced to the distal end of the member 12, tends to
straighten the distal region towards a more rectilinear
2~ orientation. The degree of advancement of the movable
core 48 towards the distal end determines the degree of
movement of the distal region from a "J" shaped
configuration towards a rectilinear orientation.
Typically, the movable core 48 is somewhat flexible, such
that even with the movable core 48 fully inserted in the
central passageway 42, the distal end still presents some
angularity (see e.g. FIGURE 4).
The Doppler mechanism 14 includes the Doppler crystal
32 secured in place by a potting compound 36 to the distal
end of the spring coil 40. In the embodiments of FIGURES
5-5 the potting compound 36 not only secures the crystal
32 to the spring coil 40, but additionally occupies a
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.;
p~rti~n of the central passa~eway 42 to effec- a seal. It
sh~ld b~ appreciated, however, that a Doppler crystal 32
c~n be donut-shaped and the potting co~pound 36 p~tially
selectively rem~ved to place the central passage~ay 42 in
co~unication with the blood stream or other biological
fluid. Such an alteration would allow the introduction of
chemicals or fluids into the blood stream, for example
angiogram dye, through the wire guide 10.
The electrical leads 16 àre connected to the Doppler
crystal 32 in similar fashion as the connections made in
the embodiment of FIGURES 1-4. In the embodiments of
FIGURES 5-8, the leads 16 are disposed in the central
passageway 42 and coupled to a connector cable or similar
device leading to an ultrasonic Doppler flow monitor.
The embodiments of FIGURES 5, 6 and 8 differ in only
minor detail. FIGURE 7 shows a cross-sectional view of
the distal end of the member 12 common to the FIGURE 5, 6
and 8 embodiments. As should be readily apparent from the
drawings, FIGURE 6 shows an embodiment in which the distal
region of the wire guide is ~straight, n while ~IGU~ES 5
and 8 show embodiments in which the distal region is in
the "J" shaped configuration. In ~IGURE 5 a movable core
48 is included, while FIGURE 8 only a fixed core 44 is
contemplated.
~se
3~
W~ile the wire guide 10 in accordance with the
present invention will undoubtedly find utility in a wide
variety of medical applications as a diagnostic tool, it
is anticipated that wire guide 10 may be particularly
advantageously used in PTCA procedures. In a typical PTCA
procedure, either a femoral or brachial approach is taken,
using a standard percutaneous procedure such as the
Seldinger approach. In most angioplasty procedures, a
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right heart catheter is inserted to m~ritor base'ine
filling pressures and ventricular paeing. Such right
heart diagnostic catheterization is relatively easy using
a balloon-tip, flow directed catheter (e.g. Swan-Ganz
catheter, Edwards Laboratory, Santa Ana, CA), in view Oc
the less stringent dimensional restrictions of the
pulmonary artery.
Manipulating the catheters and guide~ire su~selec-
tively past the ostium to perform the angioplasty is oftena difficult procedure. In most PTCA procedures, a guiding
catheter, balloon dilation catheter, and a steerable guide
wire are used. The guiding catheter is usually positioned
in the ostium of the coronary artery with the dilation
catheter positioned within the guiding catheter for
advancement over the guidewire. Most dilating catheters
have a central lumen for the sliding reception of the
guidewire, while some catheters may have an elongated open
side channel for engaging the guidewire. The guidewire is
specially designed to combine tip softness, radiographic
visability, and precise torque control so that it can be
positioned throughout the sometimes tortuous arterial tree
and stenotic regions. Because the dilating catheter
typically has a small lumen or channel, the guidewires
normally have a diameter less than .020 inches.
In the com~on PTCA procedure, baseline angiograms are
used for identifying the regions of stenoses and for
positioning the guiding catheter and dilating catheter.
The dilating catheter and the guidewire are successively
advanced through the target stenoses and positioned
relative to the lesions for evaluating by a series of
contrast injections through either the guiding catheter or
dilation catheter. Thus, the guidewire serves as a track
which permits safe advancement of the dilation catheter
through the region of the stenoses. Once the dilating
catheter is positioned, it is successively inflated
~sometimes with varying pressures) until the operator
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be1ieves t~at the sten~sis ha~ be~n r~duced. As
previously indicated, after dilatio~, th~ stenosis is
typically angiographically evaluated and this ev21uation
has proven to be somewhat deficient.
Turning to use of the wire guide 10 in accordance
with the present invention, the embodiments of FI~URES 4,
5 and 8, represent wire guide configurations which offer
the best steerability. However, all of the embodimDnts
illustrated in the drawing are positionable by torque, an~
hence steerable. In the preferred procedure, a steerable
wire guide 10 is inserted into the vessel and the dilating
catheter inserted into the vessel in operable engagement
with the wire guide 10. The wire guide 10 is manipulated
past the ostium subselectively into the coronary artery of
interest. Typically, an injection of contrast media would
be made through the dilating catheter or guiding catheter
to verify the position of wire guide 10.
The dilating catheter is shifted sequentially to
follow the wire guide 10 into the target stenotic region.
Particularly in the embodiment of FIGURE 5, the movable
core 48 is positioned in the central passageway 42 to
orient the distal end of the wire guide 10 to a desired
angularity. The member 12 is then torqued to twist the
distal end of the wire guide 10 towards the target artery
and the wire guide 10 is then advanced into the artery.
It is readily appreciated that while the wire guide
10 is being advanced, the Doppler crystal 32 is taking
continuous readings giving the operator an indication of
the blood flow velocity in the region of the distal end of
the wire guide 10. Advantageously, this constant indica-
tion of blood velocity - and hence blood flow - not
only aids in positioning the wire guide 10, but also is of
great value in determining the efficacy of the PTCA
procedure by giving an immediacy of measurement. That is,
after the dilating catheter is positioned across the
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regi~n of the target stcnosis and inflated, the ^?erator
has a constant indication of a blood flow across the
stenosis before angioplasty and after ea~h successive
inflation. Thus, the wire guide 10 in accordance with the
present invention represents a substantial advanc~ in the
art as a tool for identifying and evaluating coronary
disease, particularly in evaluating the e~ficacy of a PTCA
procedure.
As an alternative to the preferred method, the wire
guide 10 in accordance with the present invention
(particularly the embodiments of FIGURES 1 and 6) is
useful in conjunction with conventional wire guides
currently used in angioplasty. In the alternative method,
a conventional wire guide is positioned using standard
angiogram techniques and the dilating bailoon catheter
advanced into the target stenotic region. The
conventional wire guide is then removed and the wire guide
10 in accordance with the present invention inserted
through the central lumen (or along the side channel) of
the balloon catheter. Thus, the wire guide 10 is used
primarily as a tool for evaluating the efficacy of the
angioplasty, and is not used in the positioning process.
Those skilled in the art will also appreciate that
the wire guide in accordance with the present invention
has many other in vivo uses outside of the PTCA procedure.
It is readily apparent that because of its small size,
flexibility, and steerability, the wire guide 10 can
function effectively as a diagnostic probe in evaluating
blood flow or other biological fluid flow throughout the
body.
