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Description  |
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FIELD OF THE INVENTION
This invention is in the field of intraoperative and percutaneous
transluminal arterial catheters designed for surgical excision of
atheromas which typically consist of plaque deposits that cause narrowing
(stenosis) of an artery. The cutting out of atheromas has been given the
name "atherectomy".
BACKGROUND OF THE INVENTION
Atherosclerotic arterial disease is the leading cause of morbidity and
mortality in the United States and most other developed countries.
Atherosclerosis is a chronic disease process characterized by lipid
deposits and fibrosis of the intima, irregularly distributed in large and
medium sized arteries. The disease is progressive and most often becomes
clinically manifested in the middle-aged and elderly. When severe, the
atherosclerotic plaque causes a reduction of the cross-sectional area of
the arterial lumen, with and without thrombosis. Resultant ischemic
manifestations include angina pectoris, myocardial infarction, stroke,
intermittent claudication, gangrene of the lower extremities and
renovascular hypertension.
The current management of atherosclerotic disease includes preventative
therapy aimed at minimizing known major risk factors such as hypertension,
smoking, hypercholesterolemia and diabetes mellitus.
Coronary artery bypass grafting (CABG), carotid endarterectomy and bypass
grafting (autogenous vein or synthetic graft) of the iliac, femoral and
renal arteries are all well established surgical methods of palliative
therapy. Although these procedures are often effective in relieving
ischemia, each of these represents a major surgical operation with
significant associated morbidity, mortality and expense. CABG, for
example, requires the opening of the chest cavity (thoracotomy) and use of
cardiopulmonary bypass, with not uncommon postoperative complications
including postpericardotomy syndrome, Non-A Non-B hepatitis, stroke and a
mortality of approximately one percent (1%)
Percutaneous transluminal angioplasty (PTA) by means of a balloon catheter
is a relatively new "non-surgical" procedure with proven efficacy in
relief of atherosclerotic obstruction of the coronary, renal and
peripheral circulations. The technique involves the percutaneous passage
(under local anesthesia) of a specialized balloon tipped catheter through
the site of arterial narrowing, and inflation of the balloon to reduce
obstruction. This is always done in conjunction with angiographic
visualization of the vessel being treated. When successful, this procedure
results in a reduction of the arterial stenosis and a decrease in the
transstenotic pressure gradient. The mechanism of action is felt to
consist of some combination of plaque compression, intimal splitting and
medial/adventitial stretching. Healing of the balloon-damaged plaque may
involve fibrosis and retraction of the split intimal elements, with
further luminal enlargement in the weeks to months following the
procedure.
The safety and efficacy of PTA is a function of the vessel being treated,
patient selection, and the expertise of the physician performing the
procedure. Primary angiographic success, defined as a 20% or greater
reduction of stenosis, is now achieved in approximately 80-90% of attempts
in carefully selected patients at experienced centers. The obvious
advantage of PTA, compared to surgical palliative therapy, is that it does
not require major surgery or general anesthesia with the associated
sequelae.
Despite its proven efficacy in the palliation of obstructive
atherosclerotic disease, PTA, as it is currently performed, has several
important technical limitations. These limitations are particularly true
in the application of PTA to the coronary circulation.
Even in the most skilled hands, dilation of an arterial obstruction is
currently not achievable in approximately 20% of attempts. The most common
cause of failed PTA is the inability to pass either the guidewire or
dilating catheter through the site of a tight or eccentric stenosis. This
problem is even more common in attempts to dilate the difficult to access
right and circumflex coronary arteries. Although technical advances, such
as steerable catheters, have reduced the frequency of unsuccessful
attempts, inability to cross tight, eccentric or fully closed stenosis
remains a major limitation of PTA.
Attempts at balloon or guidewire passage in vessels which are tightly
stenotic may lead to arterial dissection and/or acute occlusion
necessitating emergency vascular surgery. This major complication occurs
in 6-8% of attempts at coronary angioplasty.
Inability to dilate an obstruction, even after proper balloon positioning
and inflation is a second common mode of PTA failure. This problem is most
frequently encountered in older plaques which are densely fibrotic and/or
calcified.
Restenosis of the obstructed arterial segment following successful PTA is
major problem with the current technique. This problem is more common
following PTA of a coronary obstruction (30-35% at one year) than in the
peripheral circulation (10-15% at two years). Pharmacologic attempts to
reduce the incidence of restenosis have been largely unsuccessful.
Distal embolization of atherosclerotic plaque following balloon PTA occurs
in approximately 5% of patients undergoing PTA of lower extremity or renal
arteries. Although emboli are usually clinically insignificant in these
vascular territories, such embolization could be catastrophic in the
cerebral circulation. For this reason, balloon PTA is considered to be
contraindicated for the treatment of obstructive lesions in the arteries
of the aortic arch, such as the carotid artery.
DESCRIPTION OF THE PRIOR ART
In U.S. Pat. No. 4,207,874 (dated June 17, 1980) D. S. J. Choy describes a
means for using a laser beam to tunnel though an arterial occlusion by
vaporization of the obstruction. The difficulty with Choy's technique is
that there is insufficient means to prevent simultaneous destruction of
the arterial wall. For example, the Choy invention shows an intense laser
beam aimed in the forward direction without significant beam attenuation.
If the artery were to curve and the arterial wall were to be exposed to
the laser beam, the wall could also be vaporized which could be
catastrophic for the patient. Although the Choy patent describes a means
for direct visualization of the obstructed region, it does not describe a
centering means or a guidewire following means in order to guarantee that
the laser beam does not illuminate part of the arterial wall. Furthermore,
the Choy device may completely block a partially obstructed artery thereby
cutting off blood flow to distal tissues for a significant time period.
The result is ischemia which could cause irreparable damage to heart or
brain tissue. Furthermore, if laser oblation was used in the carotid
arteries, resulting gas bubble formation could cause some cerebral
ischemia and resulting permanent brain damage.
In U.S. Pat. No. 4,273,128 (dated June 16, 1981) B. G. Lary describes a
coronary cutting and dilating instrument used for opening a coronary
stenosis that is restricting blood flow. The device described by Lary
could not be used in a completely or nearly completely occluded artery
because of its "blunt ovoid tip" nor could it pass through a very narrow
stenosis. Furthermore, the Lary concept does not have any means to prevent
its cutting blade from cutting through the arterial wall. Furthermore,
there is no means taught in the Lary patent for centering the cutting
blade within the arterial walls. Thus, if the probe wire 13 (FIG. 10) of
the Lary patent guides the knife through a highly eccentric lumen within
the stenotic plaque, its knife blade could cut through the arterial wall
resulting in serious adverse effects for the patient.
Similar to the Lary device (although actually in a different field of use,
namely removing growths from the teats of cows) is the device disclosed in
U.S. Pat. 2,730,101 (dated Jan. 10, 1956) by R. D. Hoffman and entitled
"Teat Bistoury with Expandable Cutter Knives." FIGS. 1, 2 and 3 of the
Hoffman patent show an expansible cutter knife which can be inserted
closed, opened within the teat, rotated to allow cutting of teat
obstructions and then closed to withdraw the device from the canal. The
Hoffman device has no means for preventing the blades from cutting the
vessel wall, and hence if used within a human artery, such a rotating or
oscillating blade would cut through the arterial wall. Because the flow of
milk is out of the cow's body, particulate matter released during cutting
with the Hoffman device would not harm the animal; however, in the
entirely different field of use in the artery of a human, the absence of a
definitive plaque collection means in the Hoffman device would result in
the release of particulate matter into the flowing blood. Such particulate
matter could then flow distally causing ischemia, stroke or even death.
Thus the Hoffman device is entirely unsuitable for use in human (or
animal) arteries.
Further advances are described in prior patent application Ser. Nos.
874,140 filed on June 13, 1986, and 694,746 filed on Jan. 25, 1985, both
by Robert E. and Tim A. Fischell entitled "A Guide Wire Following
Tunneling Catheter System for Transluminal Arterial Angioplasty", and "A
Tunneling Catheter System for Transluminal Arteral Angioplasty",
respectively. The '140 application describes a deice for removing stenotic
plaque by advancing a tunneling catheter over a guidewire and within a
guiding catheter. In this prior invention, the cutting is done by
advancing the cutting catheter in a forward (antegrade) direction. The
'746 application which is incorporated herein by reference, describes the
use of a centering catheter which has expandable spokes to engage the
inner arterial wall for centering the catheter. Plaque is removed by
advancing a similar tunnelling catheter described in the '140 application.
A potential difficulty in such a procedure is the inability to exert
enough forward force to cut through a hard calcified plaque. Furthermore,
if the tunneling catheter is advanced too far in the forward direction, it
could cut the arterial wall. Even with the use of cutting (as opposed to
fracturing the plaque which occurs with balloon dilation) there would
still be the possibility of some particulate matter flowing into the
bloodstream which could result in some distal ischemia.
Another application, Ser. No. 885,139 filed on July 14, 1986 by Robert E.
and Tim A. Fischell and entitled "A Pullback Atherectomy Catheter System,"
describes the concept of first penetrating the stenotic plaque in a
forward direction with a hollow conically pointed metal tip and then
pulling the tip back in a retrograde direction. The tip, which includes a
cylindrical cutting edge, is designed to shave off a cylindrical layer of
the plaque as it is pulled back in the retrograde direction. Thus, the
force required to perform the cutting is exerted by pulling back on the
catheter (a retrograde motion) as opposed to cutting with a forward
(antegrade) motion. The PAC utilizes sequentially larger diameter tips
which progressively enlarge the lumen of the stenotic plaque.
PAC devices would typically be guided to the stenosis by a guidewire that
is first passed through the narrowed lumen. Each one of the sequentially
larger PAC tips is first advanced within a guiding catheter and over a
guidewire until the tip passes through the stenotic plaque. The PAC tip is
then pulled back to shave off plaque; then the PAC is withdrawn from the
body. Each tip includes a chamber designed to collect the shaved off
plaque thus preventing plaque particles from entering the bloodstream.
Although PAC offers considerable advantage over prior atherectomy systems,
it has three distinct disadvantages. Specifically, (1) the plaque
collection chamber in the tip is both rigid and reasonably long which
makes it difficult to use in highly curved arteries, (2) the tip diameter
is limited to that diameter (approximately 3 mm) which could be readily
inserted through a percutaneous guiding catheter passing through the
femoral artery at the location of the patient's groin, and (3) to the
extent that the plaque is not elastic, the cylindrical hole made in the
plaque by the PAC tip moving in a forward (antegrade) direction precludes
the removal of plaque when the tip is moved in the retrograde direction
because the tip keeps the same diameter when moving in each of these two
directions.
SUMMARY OF THE INVENTION
It is the goal of the present invention to eliminate the numerous
shortcomings of the prior art in order to provide an extremely flexible
and expandable device which can safely tunnel a clean hole through
virtually any arterial stenosis without cutting the arterial wall or
creating gas bubbles, or causing the release of particulate matter into
the bloodstream.
The Expandable Pullback Atherectomy Catheter (EPAC) described herein
operates by first passing the EPAC through a guiding catheter that has
been intraoperatively or percutaneously inserted within an artery and then
penetrating the stenotic opening in a forward direction with the tip
diameter small enough to pass through the stenosis. When inserted into the
artery, the EPAC tip is compressed by means of a sheathing catheter that
completely encloses its tip. Once past the arterial stenosis, the
sheathing catheter, which fits inside the guiding catheter, is pulled back
thus allowing the EPAC tip diameter to radially expand to its full size.
The expanded EPAC tip is then pulled back through the stenotic plaque with
a retrograde motion while spinning which cuts through the plaque and
causes the plaque particles to be collected in a flexible plaque
collection chamber. The EPAC with the captured plaque is then pulled back
through the guiding catheter and completely out of the body. The process
is then repeated with sequentially larger expanded diameters of the EPAC
tips until the lumen of the artery is sufficiently enlarged to allow
adequate blood flow.
As described in prior application Serial No. 874,140 noted above, the
cutting action of the EPAC tip is enhanced by rotation, or by applying
high energy ultrasonic vibration to the cutting edges or possibly by the
application of an electrocautery current applied at the cutting edges.
These means for cutting enhancement would be applied only during pullback.
Thus an object of the present invention is to safely remove stenotic plaque
material by first advancing a small diameter EPAC tip through the stenotic
lumen, then allowing that tip to expand its diametric size, and then
shaving off stenotic plaque by pulling the rotating cutting edges of the
tip back through the stenosis in a retrograde direction.
Another object of the present invention is to collect the shaved off plaque
in a flexible collection chamber within the tip and then remove the entire
EPAC including the collected plaque from the body.
Still another object of the present invention is to reduce the
thrombogenicity of the plaque collection chamber by heparinizing the walls
thereof.
A further object of the present invention is to provide a plaque collection
chamber which is sufficiently porous to allow blood to flow therethrough
while still collecting all shaved plaque which could result in distal
embolization.
Still another object of the present invention is to reduce the diameter of
the EPAC tip after cutting through the stenosis so that the EPAC can be
removed through a comparatively small diameter guiding catheter.
Still another object of the present invention is to utilize ultrasonic
vibration of the cutting edges to facilitate the ability of the device to
cut through the plaque.
Still another object of the present invention is to utilize an
electrocautery electric current at the cutting edges of the EPAC tip to
enhance the ability of the device to cut through the plaque.
Still another object of the present invention is to use sequentially larger
diameter tips each sequentially pulled back through the stenotic plaque to
progressively enlarge the lumen of the stenosis.
Still another object of the present invention is to first use the EPAC to
bore a tunnel into the plaque and then use balloon angioplasty to further
enlarge the lumen of the stenotic plaque.
Still another object of the present invention is to first use balloon
angioplasty to enlarge a very narrow stenotic lumen and then to use the
EPAC to further enlarge the arterial lumen by excising the plaque.
Still another object of the present invention is to first use a heated tip
catheter or a laser beam to open a fully occluded artery and then to use
the EPAC to further enlarge the arterial lumen by excising the remaining
plaque.
Still another object of the present invention is to use the EPAC system to
remove plaque deposited at a branch point of an artery, i.e., to open an
ostial stenosis.
Still another object of the present invention is to use the EPAC to remove
thrombotic tissue from an artery or to simultaneously remove thrombotic
tissue and plaque.
Still another object of the present invention is to remove any obstructive
tissue from artificial vessel grafts or from bypass veins.
Still another object of the present invention is to apply a coating to the
EPAC that improves lubricity.
Still another object of the present invention is to apply the EPAC system
for opening of any stenotic or occluded artery including the coronary
arteries, the carotid artery, the renal, iliac or hepatic arteries and the
arteries of the arms and legs or bypass veins or vessel grafts.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates the Expandable Pullback Atherectomy Catheter (EPAC)
attached to a spinning means with the tip in its expanded state.
FIG. 2 is an enlarged, cross-sectional view through line 2-2 in FIG. 1 of
the cutting blades of the Expandable Pullback Atherectomy Catheter.
FIG. 3 is a cross-sectional view of an artery showing the Expandable
Pullback Atherectomy Catheter system with its tip located just distally
from a stenotic plaque or atheroma and with the tip in its expanded state.
FIG. 4 is a cross-sectional view of the Expandable Pullback Atherectomy
Catheter and sheathing catheter with the EPAC tip in its compressed state.
FIG. 5 is an enlarged cross-sectional view through line 5-5 in FIG. 4 of
the EPAC tip in its compressed state showing the guidewire and sheathing
catheter and also showing the plaque collection chamber in its compressed
state.
FIG. 6 shows the arrangement of the proximal portion of the Expandable
Pullback Atherectomy Catheter system as it is configured external to the
patient's body.
FIG. 7 is an enlarged cross-sectional view of the Expandable Pullback
Atherectomy Catheter of FIG. 3 showing an alternate embodiment of the
sheathing catheter.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 illustrates the Expandable Pullback Atherectomy Catheter (EPAC) 10.
FIG. 2 is an enlarged cross-sectional view of the EPAC 10 at 2--2 of FIG.
1. The other parts of the EPAC system (all shown in FIG. 3) are the
guidewire 30, the sheathing catheter 40, and the guiding catheter 50.
Referring first to FIG. 1, the principal parts of the EPAC 10 are a distal
tip 12, a radially expandable conical cutter 20, a torquing catheter 14,
and a rotating means 28. The distal tip 12 consists of a small diameter
distal portion 18 and a radially expandable plaque collection chamber 17
(FIG. 3) defined by the wall 16. The conical cutter 20 consists of a
multiplicity of cutter blades 22 that are attached at their distal ends to
distal ring 24 and at their proximal ends to the proximal ring 26. The
distal ring 24 is radially expandable and is molded into the plaque
collection chamber wall 16. Distal ring 24 takes the same cross-sectional
shape as the collection chamber 16 when expanded or compressed. The
proximal ring 26 (which is not expandable) is molded into the torqueing
catheter 14. Attachment holes 25 in the proximal ring 26 assist in
maintaining a strong connection with the wall 16 into which the ring is
molded. The proximal ring 26 has attachment holes 27 which enhance the
strength of the connection when the ring 26 is molded into the torqueing
catheter 14.
The shoulder 15 which lies over the distal ring 24 prevents the distal ring
24 and hence the conical cutter 20 from coming in contact with the
arterial wall. Thus, distal ring 24 and its shoulder 15 act as centering
devices to protect the inner arterial walls from being cut by blades 22.
Ring 24 also compensates for unequal plaque build-up along the arterial
walls by deforming appropriately as the device passes through the
stenosis. The torqueing catheter 14 is attached at its proximal end to a
spinning means 28 which is typically a drill designed for use in an
operating room; such a device could be the System II Drill, Catalogue No.
298-92 of Stryker Surgical Co., Kalamazoo, Mich.
When the EPAC 10 is pulled back through stenotic plaque while the cutter 20
is simultaneously rotated by the spinning means 28 in a counterclockwise
direction (as seen from the proximal direction) then, as seen in FIGS. 1
and 2, the longitudinal sharpened edges 29 of the blades 22 cut through
the plaque and force the plaque into the collection chamber 17. The
direction arrow R of FIG. 2 indicates the rotational direction of the EPAC
tip. A curved sharpened edge 23 of each blade 22 enhances the cutting
action by providing a slicing motion through the plaque as the EPAC is
rotated while being pulled back in a retrograde direction.
The conical cutter 20 which includes the distal ring 24 and the proximal
ring 26 is typically made from a hard spring steel, or from another spring
material such as berylium copper. The metal thickness is typically between
2 and 10 mils. The plaque collection chamber wall 16 is typically between
5 and 20 mils thick, and of a flexible plastic such as MYLAR (polyester),
TEFLON (polytetrafluoroethylene or Nylon. Ideally the wall 16 would be
made porous with pore size between 20 and 50 microns so that blood plasma,
red and white cells and platelets could pass through, thus allowing
perfusion of distal tissue to minimize risk of damaging heart tissue or
brain cells caused by lack of blood. Plaque of this small size could also
pass through with no harm to the patient. The distal ring 24 and the
plaque collection chamber is typically made in various sizes with
diameters (when expanded) from as small as 2 mm to as large as 10 mm with
total chamber length from 0.5 to 10 cm. The proximal ring 26 and torqueing
catheter 14 is typically made in various sizes with diameters ranging from
1 mm to 4 mm. The torqueing catheter 14 would typically be made from a
stiff, strong plastic such as PVC with a wall thickness between 10 and 20
mils.
Although the cutter blades 22 are shown as being essentially straight from
their smaller diameter at the proximal ring 26 to their larger diameter at
the distal ring 24, they could have a variety of shapes, positions, angles
and number of blades in order to enhance their cutting action.
FIG. 3 is a cross-sectional view of the entire EPAC system which includes
the EPAC 10, the guidewire 30, the sheathing catheter 40 and the guiding
catheter 50 all shown within an artery having an atheromatous plaque P
within the arterial wall AW. In FIG. 3 the sheathing catheter 40 is shown
pulled back so that the distal tip 12 and the conical cutter 20 have
expanded radially to their full diameter. With the aid of angiography,
after the tip 12 has been advanced beyond the stenosis, the EPAC tip 12 is
pulled back while spinning until a cylindrical tunnel has been bored
through the plaque. The plaque is collected in the plaque collection
chamber 17 and then the rotation is stopped. The EPAC 10 and the sheathing
catheter 40 are then pulled back through the guiding catheter 50 until
they are totally removed from the patient's body. A packing gland 19
typically of sponge rubber is placed to completely prevent plaque from
escaping from the plaque collection chamber 17 while the guidewire 30
remains in place and the EPAC 10 is withdrawn from the patient's artery.
However, a clearance of 20 to 50 microns between the outside diameter of
the guidewire 30 and the packing gland 19, would allow acceptably small
particulate matter to escape from the plaque collection chamber 17 as well
as allowing the flow of some blood which is desirable.
The procedure described above could be repeated if necessary with an EPAC
tip 12 that has a larger expanded diameter. This procedure can be repeated
with successively larger diameter tips 12 until the stenotic lumen is
sufficiently enlarged to allow adequate blood flow.
When the EPAC tip 12 is rotated by means of applying torque to the
torqueing catheter 14 by means of the spinning means 28 (all shown in FIG.
1), the guidewire 30 could be allowed to spin or could remain fixed.
Furthermore, the sheathing catheter 40 might be allowed to spin or it
might remain non-rotating. However, the guiding catheter 50 preferably
would remain fixed (i.e., non-rotating relative to the arterial wall AW).
Further, it may be advantageous to spin the conical cutter 20 while
slidably connecting the plaque collection chamber 17 so that the chamber
17 does not spin.
The risk of cutting the arterial wall is highest when the conical cutter is
expanded. As shown in FIG. 3, the thickness (typically 2 to 20 mils) of
the plastic material of the shoulder 15 of the plaque collection chamber
17, prevents even the largest diameter portion of the conical cutter 20
from cutting into the arterial wall.
Although the collection chamber 17 is shown in FIG. 3 to be essentially
cylindrical in shape, it might also be conical in shape with its large
mouth opening proximally. Chamber 17 also could have a much longer,
smaller diameter distal portion 18, with only a very short proximal
section of a diameter large enough to cover the distal ring 24. Designs
having a smaller diameter of the plaque collection chamber 17 as compared
to the distal ring 24, would decrease the contact of the wall 16 with the
delicate intimal lining of the arterial wall AW. This could minimize
damage to the intima during insertion, spinning and removal of the EPAC
10.
Although the spinning mode has been discussed extensively herein, the use
of ultrasonic vibration or electrocautery cutting during pullback with or
without rotation would be another practical means for accomplishing
atherectomy. For example, if the torqueing catheter 14 were fabricated
from a thin wall metal tube, such a tube could be used to transmit
ultrasonic vibration to the cutting edges 23 and 29 during pullback thus
accomplishing the desired atherectomy. In this case, an ultrasonic
vibration generator would replace the spinning means 28.
Yet another technique would be to use a metal tube torqueing catheter 14
that is insulated on all its surfaces except at its proximal end, which is
external to the body. In this technique the conical cutter 20 would be
electrically connected to the torqueing catheter 14 and would also have
electrical insulation throughout all its surfaces except at the cutting
edges 23 and 29. One terminal of a conventional electrocautery current
generator would be connected to the conducting proximal end of the
torqueing catheter 14, with the ground connection of the generator being
connected to the patient's skin. As the assembly 10 is pulled back, the
electrocautery current emanating from the sharp edges 23 and 29 would
assist in performing the desired atherectomy. Cutting with this technique
is analogous to cutting with an electrocautery scalpel as regularly used
in surgical procedures. Such an electrocautery atherectomy would have the
additional advantage of cauterizing the cut interior surface of the
arterial wall thus reducing its tendency to form thrombi.
FIG. 4 shows the sheathing catheter 40 extended over and therefore
compressing the distal tip 12 of the EPAC 10. Although the proximal ring
26 retains its precompression size, the distal ring 24 follows the plaque
collection chamber wall 16 when deformed as shown so as to fit within the
sheathing catheter 40. The distal tip 18 and the packing gland 19 of the
plaque collection chamber 17 are not compressed by the sheathing catheter
40.
When the EPAC 10 is pushed through the stenotic lumen, the sheathing
catheter 40 might be pushed through first, or alternatively the EPAC 10
could be inserted until the sheathing catheter 40 just stops proximally
against the stenosis; then the tip 12 would be pushed through. This latter
method minimizes the diameter of that which must be pushed through the
stenotic lumen. The smaller diameter distal tip 18 of the plaque
collection chamber 17 is designed for and serves to assist in passing the
distal tip 12 through a tight stenosis with the sheathing catheter 40
stopping just proximal to that stenosis.
When the distal tip 12 is pulled back through the stenotic plaque P (FIG.
3), the sheathing catheter 40 can be pushed over the distal tip 12 to
compress the tip 12. Alternatively, the guiding catheter 50 can be used to
compress the tip 12. Using the guiding catheter 50 for this purpose during
pullback would allow the greatest volume of the compressed plaque to be
held within the collection chamber 17; this would be necessary if a large
volume of plaque was collected. If such a large volume of plaque was
collected that even the guiding catheter 50 was incapable of containing
the plaque filled chamber 17, then the proximal end of the distal ring 24
would be pulled back until it touched the mouth of the guiding catheter
50, and then the entire EPAC system including the guiding catheter 50
would be removed from the patient's body | | |
