U.S. patent application number 10/819523 was filed with the patent office on 2004-10-07 for catheter apparatus having an improved shape-memory alloy cuff and inflatable on-demand balloon for creating a bypass graft in-vivo.
Invention is credited to Kim, Ducksoo.
Application Number | 20040199177 10/819523 |
Document ID | / |
Family ID | 32045784 |
Filed Date | 2004-10-07 |
United States Patent
Application |
20040199177 |
Kind Code |
A1 |
Kim, Ducksoo |
October 7, 2004 |
Catheter apparatus having an improved shape-memory alloy cuff and
inflatable on-demand balloon for creating a bypass graft
in-vivo
Abstract
The present invention provides a catheter apparatus, an improved
introducer system, and a methodology for creating a bypass
on-demand between an unobstructed blood vessel such as the aorta
and an obstructed blood vessel such as an obstructed coronary
artery in-vivo using a prepared shape-memory alloy cuff and a graft
segment in tandem as a shunt. The invention allows the placement
and creation of single or multiple bypass grafts without use of a
heart-lung machine and without need for stopping the heart of the
patient during the coronary artery bypass surgery.
Inventors: |
Kim, Ducksoo; (Dover,
MA) |
Correspondence
Address: |
David Prashker
DAVID PRASHKER, P.C.
P.O. Box 5387
Magnolia
MA
01930
US
|
Family ID: |
32045784 |
Appl. No.: |
10/819523 |
Filed: |
April 7, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10819523 |
Apr 7, 2004 |
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09472711 |
Dec 24, 1999 |
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6719781 |
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09472711 |
Dec 24, 1999 |
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09060958 |
Apr 16, 1998 |
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6007544 |
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10819523 |
Apr 7, 2004 |
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08702068 |
Aug 23, 1996 |
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5797920 |
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08702068 |
Aug 23, 1996 |
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08664165 |
Jun 14, 1996 |
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5676670 |
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Current U.S.
Class: |
606/108 |
Current CPC
Class: |
A61F 2002/821 20130101;
A61F 2002/8486 20130101; A61B 17/3207 20130101; A61F 2/958
20130101; A61F 2/95 20130101; A61B 2017/00243 20130101; A61B
2017/00867 20130101; A61B 17/320016 20130101; A61M 2205/0266
20130101; A61B 17/00491 20130101; A61B 2017/00292 20130101; A61B
2017/1107 20130101; A61B 2017/1135 20130101; A61M 25/0032 20130101;
A61F 2/07 20130101; A61F 2210/0019 20130101; A61F 2/90 20130101;
A61M 2025/0233 20130101; A61B 2018/00392 20130101; A61B 2017/00247
20130101; A61B 17/11 20130101; A61F 2/0077 20130101; A61F 2002/061
20130101; A61F 2/064 20130101; A61B 2017/00778 20130101; A61F
2210/0014 20130101; A61F 2210/0023 20130101; A61F 2002/8483
20130101; A61B 17/3417 20130101; A61F 2002/30092 20130101 |
Class at
Publication: |
606/108 |
International
Class: |
A61M 029/00 |
Claims
What I claim is:
1. 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 invivo to a chosen site wherein an unobstructed
blood vessel is in anatomic proximity 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 (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 a thermoelastic deformable 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 central 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 central 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. (iv) and whereby the end of the graft
segment engaged by the central portion of the cuff becomes secured
to and placed in blood flow communication with the unobstructed
blood vessel and serves as a conduit means for bypassing an
obstruction and restoring blood flow from the unobstructed blood
vessel to an obstructed blood vessel.
2. 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 invivo to a chosen site wherein an unobstructed
blood vessel is in anatomic proximity 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 (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; an inflatable and deflatable on-demand balloon of
prechosen configuration disposed adjacent to said puncturing
headpiece on said elongated shaft of said 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 segment to be used as a conduit,
said thermoelastic deformable cuff having a discrete central
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 central
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 central 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, (iv) and
whereby the end of the graft segment engaged by the central portion
of the cuff becomes secured to and placed in blood flow
communication with the unobstructed blood vessel and serves as a
conduit means for bypassing an obstruction and restoring blood flow
from the unobstructed blood vessel to an obstructed blood
vessel.
3. 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 invivo to a chosen site wherein an unobstructed
blood vessel is in anatomic proximity 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 (a) a puncturing headpiece for puncture
of and entry into the lumen of an unobstructed blood vessel, (b) a
perforating end tip of 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; an inflatable and deflatable on-demand balloon of
prechosen configuration disposed adjacent to said puncturing
headpiece on said elongated shaft of said 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 a chosen extant configuration for positioning over said
elongated shaft adjacent to said puncturing headpiece of said
obturator together with a graft segment (i) wherein, prior to the
perforation of the unobstructed blood vessel in-vivo by said
puncturing headpiece of said obturator, a portion of said cuff in
the extant configuration 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 cuff portion and a plurality
of 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, at least part of said
non-engaged cuff end portion is extended into the lumen of the
unobstructed blood vessel and becomes thermoelastically deformed
in-situ into a prepared memory-shaped end configuration, and said
prepared memory-shaped end configuration of said deformed
non-engaged cuff portion becomes disposed onto an interior surface
of the unobstructed blood vessel, (iii) and whereby said cuff
engaged end of the graft segment 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.
4. The catheter apparatus as recited in claim 1, 2, or 3 wherein
said deformable cuff is comprised of a nickel-titanium alloy.
5. The catheter apparatus as recited in claim 1, 2, or 3 wherein
said deformable cuff is overlaid with a biocompatible coating.
6. The catheter apparatus as recited in claim 1, 2, or 3 wherein
said deformable cuff comprises an open meshwork.
7. The catheter apparatus as recited in claim 1, 2, or 3 wherein
said deformable cuff comprises a solid mass of material.
8. The catheter apparatus as recited in claim 1, 2, or 3 wherein
said obturator further comprises means for expansion and
contraction of said puncturing headpiece on-demand.
9. The catheter apparatus as recited in claim 1, 2, or 3 wherein
said graft segment comprises a synthetic prosthetic channel
section.
10. The catheter apparatus as recited in claim 1, 2, or 3 wherein
said graft segment comprises a previously excised blood vessel
segment.
11. The catheter apparatus as recited in claim 2 or 3 wherein said
balloon comprises means for conveying fluid.
12. The catheter apparatus as recited in claim 2 or 3 wherein said
balloon comprises an enclosing sheath.
13. The catheter apparatus as recited in claim 2 or 3 wherein said
balloon is composed of at least one material selected from the
group consisting of elastic and non-elastic substances.
Description
CROSS REFERENCE
[0001] The present application is a Continuation-In-Part of U.S.
patent application Ser. No. 702,068 filed Aug. 23, 1996, now
allowed; which was a Continuation-In-Part of U.S. patent
application Ser. No. 664,165 filed Jun. 14, 1996, now U.S. Pat. No.
5,676,670 issued Oct. 14, 1997.
FIELD OF THE INVENTION
[0002] 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 or vein
in-vivo.
BACKGROUND OF THE INVENTION
[0003] 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 oxygen supply. Sometimes it can also
completely stop the blood flow to the heart causing permanent
damage to the myocardium, the so-called "heart attack."
[0004] 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, atherectomy devices or 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.
[0005] 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.
[0006] One of the medically accepted ways to deal with coronary
arterial blockage is percutaneous transluminal coronary angioplasty
(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 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.
[0007] 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.
[0008] The most common blood vessel harvested for use as a graft is
the greater (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 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.
[0009] 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 patency 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.
[0010] 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 gallbladder 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 laparoscope. Initially, a three-inch incision is
made to the left of the breast bone through which the 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.
[0011] As a bypass graft, the left internal mammary artery (LIMA)
offers a number of advantages to the saphenous vein graft including
higher patency 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.
[0012] 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.
[0013] 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
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
[0014] 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:
[0015] 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 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;
[0016] 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
[0017] (a) a puncturing headpiece for puncture of and entry into
the lumen of an unobstructed blood vessel,
[0018] (b) a perforating end tip on said puncturing headpiece to
facilitate the perforation of a blood vessel wall at the chosen
site in-vivo,
[0019] (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
[0020] a thermoelastic deformable 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
[0021] (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,
[0022] (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,
[0023] (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.
[0024] (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.
[0025] A second aspect of the present invention 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:
[0026] 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 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;
[0027] 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
[0028] (a) a puncturing headpiece for puncture of and entry into
the lumen of an unobstructed blood vessel,
[0029] (b) a perforating end tip on said puncturing headpiece to
facilitate the perforation of a blood vessel wall at the chosen
site in-vivo,
[0030] (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;
[0031] an inflatable and deflatable on-demand balloon of prechosen
configuration disposed adjacent to said puncturing headpiece on
said elongated shaft of said 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
[0032] 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 segment to be
used as a conduit, said thermoelastic deformable cuff having a
discrete medial portion and two discrete end portions
[0033] (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 then carried by
said elongated shaft of said obturator thereby forming an engaged
medial cuff portion and two discrete non-engaged cuff end
portions,
[0034] (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,
[0035] (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,
[0036] (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 FIGS.
[0037] The present invention may be more easily and completely
understood when taken in conjunction with the accompanying drawing,
in which:
[0038] FIG. 1 is an overhead view of a conventionally known first
catheter;
[0039] FIG. 2 is an overhead view of a conventionally known second
catheter;
[0040] FIGS. 3A and 3B are perspective and cross-sectional views of
a single wall catheter tube of normal thickness;
[0041] FIGS. 4A and 4B are perspective and cross-sectional views of
a single wall catheter tube of reduced thickness;
[0042] FIGS. 5A and 5B are perspective and cross-sectional views of
a multiple-wall catheter tube of normal thickness;
[0043] FIGS. 6A and 6B are perspective and cross-sectional views of
a multiple-wall catheter tube of reduced thickness;
[0044] FIGS. 7A-7D are cross-sectional views of four different
constructions of dual-lumen catheters;
[0045] FIG. 8 is an illustration of a conventionally known
introducer catheter;
[0046] FIG. 9 is a perspective view of a preferred first
obturator;
[0047] FIG. 10 is a frontal view of the first obturator of FIG.
9;
[0048] FIG. 11 is a side view of the puncturing headpiece of the
first obturator shown in FIG. 9;
[0049] FIG. 12 is a side view of the puncturing headpiece of FIG.
11 when in a contracted state;
[0050] FIG. 13 is a side view of the puncturing headpiece of FIG.
11 when in an expanded state;
[0051] FIG. 14 is an exposed view of a mechanical assembly used for
expanding and contracting a puncturing headpiece on-demand in an
obturator;
[0052] FIG. 15 is an exposed view of a hydraulic assembly for
expanding and contracting a puncturing headpiece on-demand in an
obturator;
[0053] FIG. 16 is a perspective view of a second obturator;
[0054] FIG. 17 is a frontal view of the second obturator of FIG.
16;
[0055] FIG. 18 is a perspective view of a third obturator;
[0056] FIG. 19 is a frontal view of the third obturator of FIG.
18;
[0057] FIG. 20 is a side view of an alternative fourth puncturing
headpiece of an obturator;
[0058] FIG. 21 is a side view of an alternative fifth puncturing
headpiece of an obturator;
[0059] FIGS. 22A and 22B are side and top views of an alternative
sixth obturator;
[0060] FIGS. 23A and 23B are overhead and side views of a small-box
pattern meshwork'
[0061] FIGS. 24A and 24B are overhead and side views of a large-box
pattern meshwork;
[0062] FIGS. 25A and 25B are overhead and side views of a nets
patterns meshwork;
[0063] FIGS. 26A and 26B are overhead and side views of a brick
pattern meshwork;
[0064] FIGS. 27A and 27B are overhead and side views of a spiral
pattern meshwork;
[0065] FIGS. 28A and 28B are overhead and side views of a honeycomb
pattern meshwork;
[0066] FIG. 29 is a view of a circular and smooth cuff end
perimeter outline;
[0067] FIGS. 30A and 30B are views of large and small petaloid cuff
end perimeter outlines;
[0068] FIG. 31 is a view of a bare wire endpoint perimeter for a
cuff end;
[0069] FIGS. 32A-32C are views of a preformed first cuff embodiment
in the extant and prepared memory-shaped configurations;
[0070] FIGS. 33A-33C are views of a preformed second cuff
embodiment in the extant and prepared memory-shaped
configurations;
[0071] FIGS. 34A-34C are views of an alternative cuff end perimeter
outline for the embodiment of FIG. 33;
[0072] FIGS. 35A-35C are views of a third preformed cuff embodiment
in the extant and prepared memory-shaped configuration;
[0073] FIGS. 36A-36D are views of an alternative fourth cuff
embodiment in the extant and prepared memory-shaped
configurations;
[0074] FIGS. 37A-37B are views of an alternative fifth cuff
embodiment in the extant and prepared memory-shaped
configurations;
[0075] FIGS. 38A-38C are views of an alternative sixth cuff
embodiment in the extant and prepared memory-shaped
configurations;
[0076] FIGS. 39A and 39B are cross-sectional and side views of an
inflatable and deflatable on-demand balloon;
[0077] FIGS. 40A and 40B are overhead and side views of an
inflatable and deflatable balloon of FIG. 39 properly positioned on
an obturator;
[0078] FIGS. 41A and 41B are overhead and side views of the
positioned balloon of FIG. 40 in the inflated state;
[0079] 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;
[0080] FIG. 43 is a perspective view of the preferred first cuff
embodiment of FIG. 23A in combination with the previously excised
vascular segment as shown by FIG. 42;
[0081] FIG. 44 is a partially exposed view of the improved
introducer system as a whole;
[0082] FIGS. 45A-45F are illustrations of the modified Seldinger
technique conventionally used for percutaneous
catherterization;
[0083] FIG. 46 is a partially exposed view of the improved
introducer system in the correct position at the exterior wall of
an unobstructed blood vessel in-vivo;
[0084] FIG. 47 is a partially exposed view of the improved
introducer system penetrating the vascular wall of the unobstructed
blood vessel in-vivo;
[0085] FIG. 48 is a partially exposed view of the improved
introducer system within the internal lumen of the unobstructed
blood vessel in-vivo;
[0086] 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;
[0087] 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;
[0088] 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;
[0089] 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;
[0090] 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
[0091] 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
[0092] 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 introducer 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, some of which
include the following:
[0093] 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 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 the surgery.
[0094] 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.
[0095] 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
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, 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.
[0096] 4. The present apparatus and methodology can be employed to
create a 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. However, a bypass shunt may also be
created between any two veins (such as between the portal vein and
the inferior vena 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 vascularization or revascularization of the
local region. The sole limitation, therefore, is a means of access
for the catheter apparatus, the introducer system, and the
methodology to be performed by the skilled surgeon and
interventional radiologist.
[0097] In order to provide a complete and comprehensive
understanding of the 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 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.
[0098] I. The Component Parts of the Catheter Apparatus
[0099] 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 for 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.
[0100] A. The Catheter
[0101] The in-vivo bypass catheterization method comprising the
present invention requires that a guiding or introducer catheter be
employed as an essential part of the apparatus and manipulations.
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 lumen of a volume sufficient to allow for on-demand
controlled passage therethrough of a prepared obturator carrying a
deformable thermoelastic cuff and a bypass conduit.
[0102] 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 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 cathertization
techniques. Merely representative of the diversity of publications
publicly available are the following, each of which is expressly
incorporated by reference herein: Diagnostic and 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
et. al., editors) Little, Brown, and Company, 1995 and the
references cited therein; Abrams Angiography, third edition (H. L.
Abrams, editor), Little, Brown, and Company, 1983.
[0103] 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 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.
[0104] Catheter Construction and Design:
[0105] Presently known specific types of catheters include the
following: central venous catheters which are relatively 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 for cardiac catheterization and
angiography in any of the major vessels; coronary angiographic
catheters which include the different series of grouping including
Sones, Judkins, Amplatz, multipurpose, and bypass graft catheters;
as well as many others developed for specific purposes and medical
conditions.
[0106] Merely representative of guiding and introducer 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 is seen
having a tubular wall of fixed axial length; having two proximal
portals 4 and 6 which together generate the proximal end 8 for
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).
[0107] 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
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.
[0108] 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
multilayered 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 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.
[0109] 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 catheter. FIGS.
4A and 4B are perspective and cross-sectional views of a
thin-walled design for a single layer extruded catheter. In
comparison, FIGS. 5A and 5B 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.
[0110] 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 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 3.0.
Conversely, by traditional habit, the size of any catheter in
millimeters may be calculated by dividing its French size by a
factor of 3.0. 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 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.
1TABLE 1 External and Lumen Diameter Measurements in Standard,
Thin-Walled, and Super High-Flow Diagnostic Catheters Internal
Diameter Standard Thin-Walled Super French External Diameter (High
Torque) (High Flow) (High Flow) Size inches mm inches mm inches mm
inches mm 5 0.065 1.67 a a 0.044 1.08 0.052 1.28 6 0.078 2.00 a a
0.050 1.27 0.056 1.42 7 0.092 2.34 0.048 1.22 0.056 1.42 0.061 1.55
8 0.104 2.64 0.056 1.42 0.063 1.60 a a 9 0.118 3.00 a a a a a a a
No catheters made in this size/type.
[0111] Dual-Lumen Catheters:
[0112] 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.
[0113] 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.
[0114] 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.
[0115] 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 smaller than the volume of the adjacently positioned
internal lumen 58; and yet both of these internal lumens 56 and 58
exist in, are adjacently positioned, and are both contained within
a commonly-shared single tubular wall.
[0116] 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 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.
[0117] Introducer Catheters and Catheter Ends:
[0118] In general, an introducer catheter is straight or linear
over its 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.
[0119] 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 98 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.
[0120] B. The Obturator
[0121] 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.
[0122] 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 fixed or varied
in size. At the 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
130 serves as the sharp cutting edge for the obturator 120 as a
whole.
[0123] 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 of the
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 134 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 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.
[0124] The Fixed Size Embodiments of the Obturator
[0125] The minimalist format for the obturator does not 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.
[0126] The Variable-Size Embodiments of the Obturator
[0127] 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.
[0128] When the mechanism for contracting the puncturing headpiece
is activated, the consequence is illustrated by FIG. 12 in which
the dimensions 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 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.
[0129] 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.
[0130] 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.
[0131] Means for Contracting or Expanding the Puncturing
Headpiece
[0132] A feature and component of each preferred obturator is the
existence and availability of specific means for expanding and
contracting the puncturing 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.
[0133] 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. Each 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
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.
[0134] 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 122 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 134 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.
[0135] 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 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 on 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.
[0136] Alternative Obturator Structures
[0137] 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.
[0138] 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 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.
[0139] 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 provides a much greater area for cutting and
perforation as a specific feature of the obturator design.
[0140] 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).
[0141] 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.
[0142] 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-shaped configuration of the distal tip 284 is intended
to aid the puncturing headpiece as it is expanded and contracted
on-demand.
[0143] II. The Deformable Thermoelastic Cuff
[0144] 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.
[0145] 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-memory
alloys is that these alloys after pretreatment will change shape or
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.
[0146] 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 able to revert into a prepared memory-shaped
configuration merely by being warmed to a temperature above its
individual transition temperature.
[0147] Alloy Formulations
[0148] 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 [Design News, Jun. 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, Calif.].
In addition, surgical anchors having superelastic properties and
formed by two or more arcs of wire strands (which can withstand
strains exceeding 10%) have been developed [Mitek Surgical
Products, Inc., Norwood, Mass.]. 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, Mass.]. 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.
2TABLE 2 Conventionally Known Properties Of Shape-Memory
Alloys.sup.1 Transformation Properties Transformation Temperature
-200 to 110.degree. C. Latent Heat Of Transformation 5.78 cal/g
Transformation Strain (for polycrystaline material) for a single
cycle 8% maximum for 10.sup.2 cycles 6% for 10.sup.5 cycles 4%
Hysteresis* 30 to 50.degree. C. Physical Properties Melting point
1300.degree. C. (2370.degree. F.) Density 6.45 g/cm.sup.3 (0.0233
lb/in.sup.3) Thermal Conductivity austenite 0.18 W/cm .multidot.
.degree. C. (10.4 BTU/ft .multidot. hr .multidot. .degree. F.)
martensite 0.086 W/cm .multidot. .degree. C. (5.0 BTU/ft.
.multidot. .degree. F.) Coefficient of Thermal Expansion austenite
11.9 .times. 10.sup.-6/.degree. C. (6.11 .times. 10.sup.-6/.degree.
F.) martensite 6.6 .times. 10.sup.-6/.degree. C. (3.67 .times.
10.sup.-6/.degree. F.) Specific Heat 0.20 cal/g .multidot. .degree.
C. (0.20 BTU/lb .multidot. .degree. F.) Corrosion Performance**
excellent Electrical Properties Resistivity (p) [resistance = p
.multidot. length/cross-sectional area] austenite .about.100
.mu..OMEGA. .multidot. cm (.about.39.3 .mu..OMEGA. .multidot. in)
martensite .about.80 .mu..OMEGA. .multidot. cm (.about.31.5
.mu..OMEGA. .multidot. in) Magnetic Permeability <1.002 Magnetic
Susceptibility 3.0 .times. 10.sup.6 emu/g Mechanical Properties
Young's Modulus*** austenite .about.83 GPa (.about.12 .times.
10.sup.6 psi) martensite .about.28 to 41 GPa (.about.4 .times.
10.sup.6 to 6 .times. 10.sup.6 psi) Yield Strength austenite 195 to
690 MPa (28 to 100 ksi) martensite 70 to 140 MPa (10 to 20 ksi)
Ultimate Tensile Strength fully annealed 895 MPa (130 ksi) work
hardened 1900 MPa (275 ksi) Poisson's Ratio 0.33 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 temary alloys. **Similar to 300 series stainless
steel or titanium. ***Highly nonlinear with temperature.
.sup.1Design News. Jun. 21, 1993 issue, p. 77.
[0149] All the different specific formulations and metallic blends
comprising nickel and titanium which yield a deformable,
thermoelastic, shape-memory alloy composition are suitable for use
when practicing the present methodology. All 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).
[0150] The crystal transformation of shape-memory alloy
compositions is, by definition, thermoelastic--i.e., 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 percent of Martensite form or the strain in a
constantly stressed element, is a function of and can be plotted
against temperature (.degree. C.) directly; and the change from one
phase (and identifiable shape) to another typically occurs in a
narrow temperature range (often 5-10.degree. C.) Hysteresis takes
place before the reverse transformation occurs.
[0151] 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%.
[0152] 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.
[0153] Fixing the Memory-Shaped Configuration in the Metal
Alloy
[0154] To prepare and fix the particular (or desired) shape to be
"remembered" when the alloy undergoes a temperature phase
transition, the alloy composition must be superheated initially to
about 300-600.degree. C. for between 30 minutes-3 hours while held
in the shape and position to be memorized. During 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.degree. C., thermal motion causes the atoms to
snap back into the Austerine phase, thereby restoring the
previously fixed memory-shaped configuration of the object. 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].
[0155] 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.degree. C.; but greater than about 25.degree. C.; and
preferably be in the range from about 30-35.degree. C. This
preferred 30-35.degree. C. transition phase temperature range is
dictated by the demands of the human body which maintains a normal
temperature at about 37.degree. C. (98.6.degree. F.); and typically
shows a normal temperature range and variance of one or two degrees
Celsius above and/or below this normative temperature standard. It
is for this reason that the broad temperature range be about
25-35.degree. C. and the preferred temperature transition occur in
the range of 30-35.degree. C.; but that such transformation into
the prepared fixed memory-shaped configuration occur at least by a
temperature of 35.degree. C. to insure a safety margin of medical
usefulness.
[0156] The Alloy Cuff Structure and Embodiments
[0157] 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 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.
[0158] 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.
[0159] 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 as the cuff body is shown in
an overhead view and in a cross-sectional view. Thus, FIGS. 23A and
23B illustrate a squareline pattern for the wire meshwork while
FIGS. 24A 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.
[0160] 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
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 30B 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.
[0161] 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 all 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.
[0162] The Extant Shape and the Memory-Shaped Deformed
Configuration
[0163] 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 outline
appearing at ambient temperatures less than about 25-35.degree. 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.degree. C. The range and
variety of some useful extant shapes and memory-shaped
configurations is described in detail hereinafter.
[0164] 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 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.degree. 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.
[0165] 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.degree. C. By
definition, the memory-shaped configuration is that form 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.
[0166] 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.degree. C. range; and that the
structure of the alloy cuff need not become thermoelastically
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 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.degree. 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.degree. C. will
cause that component portion or section of the cuff
thermoelastically to deform into its prepared memory-shaped
configuration imprinted previously.
[0167] The Configurations of the Prepared Alloy Cuff at
Temperatures Less Than 25-35.degree. C. and at Temperatures Greater
than 25-35.degree. C.
[0168] The extant cuff configurations of the pretreated and
prepared thermoelastic alloy composition at temperatures less than
about 25-35.degree. 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.degree. 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.
[0169] As illustrated and embodied by FIGS. 32A, 32B, and 32C
respectively, the deformable 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.degree. C. which are
deformed at will into a memory-shaped configuration when placed at
a temperature greater than about 25-35.degree. C.
[0170] 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 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.
[0171] 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.degree. C. and
sequentially exposing different sections to a temperature
environment greater than about 25-35.degree. 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 312 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 deformable thermoelastic cuff.
[0172] 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.degree.
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.
[0173] 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; (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.degree. 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 unaltered form 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.
[0174] 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:
[0175] (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 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 more 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 thermoelastic alloy material is left solely to the
discretion of the manufacturer and the surgeon.
[0176] (b) The thermoelastic 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.
[0177] (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. Shape-memory
alloys can also be made radioactive to minimize tissue reactions. A
representative listing of biocompatible coatings deemed suitable
for use with the deformable thermoelastic cuff is provided by Table
3 below.
3TABLE 3 Biocompatible Coatings High temperature pyrongen-free
carbon; Polytetrafluoroethylene (PTFE) and other polyhalogenated
carbons; Fibronection; Collagen; Hydroxyethyl methacrylates (HEMA);
Serum albumins; Suprafilm (Genzyme Corp.); Silicone polymer;
Polyurethanes; Tetrathane (Dupont); Polytetramethylene polymers;
Dacron; Polyesther woven fabric; and Polycarbonated urethanes.
[0178] (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 not 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 maybe 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.
[0179] To illustrate some of the modest variations and differences
available and envisioned for a deformable thermoelastic cuff
intended for use with the present invention, the alternative cuff
embodiments illustrated by FIGS. 33-38 are provided. A particular
feature is shown within FIGS. 33 and 34 where the extant shape for
the 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.
[0180] 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 338 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 338 and 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.degree. C.
[0181] The result of thermal deformation in-situ of individual
sections and portions of the cuff at a temperature greater than
about 25-35.degree. 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
juncture concurrently to the internal lumen and exterior surface of
an artery or vein in-vivo.
[0182] 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.degree. 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.degree. 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.
[0183] The consequence of advancing the coiled cuff 360 in sections
into an ambient temperature greater than about 25-35.degree. C. is
shown by FIGS. 35B and 35C. It will be appreciated that the
partially-induced, memory-shaped configuration of 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 CC' 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.degree.
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.
[0184] The fourth alternative embodiment of a thermally deformable
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 25.degree. 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.degree. 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.
[0185] The consequence of placing the prepared alloy cuff 380 in
sections into temperatures greater than about the 25-35.degree. C.
range is illustrated by FIGS. 36B, 36C, and 36D. As shown by FIG.
36B, 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.degree. 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.
[0186] 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.degree. C. as an open 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.degree. 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 thermoelastically at the elevated temperature
from about the axis HH' to the other open end 394. These features
are illustrated by FIG. 37A.
[0187] The consequence of advancing the prepared alloy cuff 390 as
different sections into temperatures greater than about the
25-35.degree. 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.degree.
C. temperature zone, the other open end 394 and sidewall 398 also
thermoelastically deform and become bent outwardly such that the
bare wire pointed 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.
[0188] 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.degree. 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.degree. 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.
[0189] The consequence of advancing the prepared alloy cuff 400 as
different sections into temperatures greater than about the
25-35.degree. C. range is illustrated by FIGS. 38B and 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.degree. 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.degree. C. temperature environment.
[0190] III. The Inflatable And Deflatable On-Demand Balloon
[0191] 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.
[0192] 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 multi-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.
[0193] 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 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.
[0194] 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 426 is hollow and will
assume a substantially rounded appearance as the balloon 420
becomes inflated. At least one inflation/deflation 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.
[0195] 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 to
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.
[0196] The inflated state for the balloon is shown by FIGS. 41A and
41B 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 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.
[0197] 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.
[0198] IV. The Bypass Graft Material
[0199] 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.
[0200] 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 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 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.
[0201] A. Synthetic Conduits
[0202] 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.
[0203] The medical value of synthetic conduits as bypass grafts
in-vivo has been substantially investigated. See for example:
Foster et. al., Circulation 79 (Sup 1): 134-139 (1989); and Canver,
C. C., Chest 108: 1150-1155 (1995); and the other references cited
below. A summary review of the recent reports evaluating these
conduits thus is in order.
[0204] Historically, Sauvage and associates in 1976 [J. Thorac.
Cardiovasc. Surg. 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 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.
[0205] The initial results of CABG with expanded
polytetrafluoroethylene (PTFE) (Gore-Tex. W. L. Gore and
Associates, Elkton, Md.) 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 [J. Thorac.
Cardiovasc. Surg. 75: 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 catheterization
3 months after surgery. Also, Yokoyama and associates in 1978 [J.
Thorac. Cardiovasc. Surg. 76: 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.
[0206] 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. Cardiovasc. Surg. 81: 860-864 (1981)].
Twenty-seven coronary bypasses were constructed in 16 patients with
4.0-mm PTFE grafts. Eleven patients were restudied at 3 months
after surgery, and a 61% (11 of 18) graft patency rate was found,
in six patients who had repeat angiography 12-29 months after CABG,
six of nine PTFE grafts were open. Then, Murta and co-authors in
1985 [Ann. Thorac. Surg. 39: 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. Thorac. Cardiovasc. Surg. 94:
132-134 (1987)] long-term patency 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. Patency rates on repeat
angiography were 64% (18 of 28) at 1 year, 32% (9 of 28) at 2
years, 21% (6 of 28) at 3 years, and 14% (4 of 28) at 45
months.
[0207] 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.
[0208] B. The Excised Blood Vessel Segment
[0209] 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.
4TABLE 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.
[0210]
5TABLE 5 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). Nonautologous vein conducts. Umbilical vein
segments; Greater saphenous vein homografts. Arterial Conduits (a).
Autologous arterial conduits. Internal mammary artery segments;
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.
[0211] 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.
[0212] 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.degree. to 10.degree. C.) and 10,000 units/liter of
heparin. A valvulotome is inserted into the vein graft segment and
the valves 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.
[0213] V. The Introducer System
[0214] The introducer system comprises the catheter apparatus
including the thermoelastic deformable cuff and a bypass conduit in
combination; and it is this introducer system which is utilized by
the surgeon to perform the requisite acts and 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
comprehension, this description will intentionally limit itself to
the use of the variable-sized obturator 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 introducer
system represents and provides for the intentional placement and
carriage of the bypass conduit on the obturator, the engagement and
juncture 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.
[0215] The preferred introducer system begins with the proper
placement of a previously excised vascular segment (desirably taken
from the saphenous vein) upon the obturator 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 126 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 manner, the weight and body of
the excised vascular segment 460 is carried on the elongated shaft
134; and it is desirable that the 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.
[0216] 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 alignment and posture and in a more controlled manner of
deformation on-demand.
[0217] 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 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.
[0218] Other means for permanent engagement and juncture of the
thermally deform able 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.
[0219] One optional variation of the introducer system provides
that the open 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.
[0220] In addition, another optional variation of the introducer
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.
[0221] 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 126 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 122 serves as a front section or first stage
for the introducer system as a whole.
[0222] The complete introducer 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 introducer
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 lumen 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 introducer 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 introducer catheter. The
introducer system shown by FIG. 44 is complete; and the surgeon may
now begin the first steps for surgically delivering the introducer
system into the thoracic cavity or other appropriate body region in
order to create the bypass graft.
[0223] Maintaining the Ambient Temperature of the Internal Lumen of
the Catheter at Less than About 25-35.degree. C.
[0224] The preferred means for cooling and maintaining the
temperature of the internal lumen in a guiding catheter comprising
the introducer system at less than about 25-35.degree. C. during
the creation of a bypass graft in-vivo is via the use of cold
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 40-50.degree. F. (5-10.degree. 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 introducer system or the
patient.
[0225] 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 the
environmental temperature of the internal lumen volume of a
catheter at less than about 25-35.degree. 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.degree. C. can be safely and
properly performed in many different medical circumstances using
the present invention.
[0226] VI. The Routing and Surgical Introduction of the Controlling
Catheter into the Body of the Living Human
[0227] 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.
[0228] 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 and the critical
route of access is the introduction of catheters into the thoracic
cavity and the arterial blood circulation adjacent to the
heart.
[0229] For this reason, it is useful to briefly summarize the
technique currently in use for introduction of catheters into the
central blood 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 introducer 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.
[0230] The Modified Seldinger Technique:
[0231] 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. 45C.
Subsequently, a sheath and a dilator is placed over the guidewire
as shown by FIG. 45D. 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.
[0232] 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.
[0233] 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.
[0234] General Rules for Choosing an Appropriate Site of Body
Entry:
[0235] 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.
[0236] A Favored Approach to Introducing the Guiding Catheter into
the Thoracic Aorta:
[0237] Using the ascending aorta approach as a representative
illustration and example:
[0238] (1) Under general anesthesia, the chest of the patient is
prepared and draped in a sterile fashion.
[0239] (2) A three-inch incision is made to the left or right of
the breast bone through which the surgeon operates.
[0240] (3) Three additional one-inch incisions then are made to
insert a video camera, knife, surgical stapler, and other
instruments.
[0241] (4) The ribs are separated, the thoracic cavity is entered,
and the ascending thoracic aorta is exposed.
[0242] (5) The introducer system is then positioned at the chosen
site on the ascending thoracic aorta.
[0243] (6) The penetration can be monitored by an ultrasound
apparatus placed in the esophagus.
[0244] VI. The In-Vivo Placement of the Vascular Bypass Graft into
The Lumen of the Unobstructed Major Blood Vessel
[0245] The method of the present invention utilizes the introducer
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.
[0246] After the introducer 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. 47-54 respectively) are shown as partially exposed
views in order to show more easily the detailed placement and
orientation of the introducer system comprising an obturator with
positioned balloon carrying the improved deformable cuff and
previously excised vascular segment in combination.
[0247] As seen within FIG. 46, a major artery such as the aorta 500
is shown in 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 introducer
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 are in axial alignment 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.degree. C. (using cold saline or gaseous carbon
dioxide), and is properly placed for piercing and penetrating the
arterial wall on-demand.
[0248] When 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 obturator
(complete with thermally deformable cuff and excised blood vessel
segment in combination) can subsequently pass through the enlarged
hole in the arterial wall.
[0249] As the prepared obturator is extended further across the
thickness of the arterial wall 502 through the enlarged passage,
the penetrating headpiece 122 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 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.
[0250] 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
catheters 82 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.
[0251] 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.
[0252] 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.
[0253] 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.
[0254] 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 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.
[0255] 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
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.degree. C.,
begins to deform thermally into the memory-shaped second
configuration.
[0256] 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. 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.degree. C. of the arterial lumen thus is the choice and
judgment of the surgeon at all times. It can be monitored and also
guided by a transesphogeal ultrasound, which is commonly used
during current cardiac surgeries.
[0257] 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 300 will thermally
deform in-situ into the memory-shaped second configuration--as
shown by FIG. 50. The warm temperature environment above 35.degree.
C. of the arterial lumen has caused the upper sidewall 308 of the
cuff to deform in-situ; to become bent outwardly, and to become
flaired 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 will
become secured to the arterial wall in a permanent manner. This
consequence and result is also illustrated by FIG. 50.
[0258] 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
lumen 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.degree. 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.
[0259] 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.
[0260] 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 both 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 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.
[0261] A number of different biocompatible adhesives may be
employed to seal permanently the puncture site in the manner shown
by FIG. 53. A representative but non-exhaustive listing of such
biocompatible adhesives is provided by Table 6 below.
6TABLE 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.).
[0262] 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 juncture 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.
[0263] 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.
[0264] The entire catheterization methodology for creating a
vascular bypass graft or shunt has been shown and described in
detail via FIGS. 46-54 inclusive. Each essential manipulation or
required act has been illustrated in detail and described in 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
introducer system, and the methodology is provided hereinafter.
[0265] VI. Summary of the Preferred Surgical Procedures Using the
Catheter Apparatus and Method
[0266] 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
introducer system which internally carries a deformable cuff and a
previously excised vascular segment.
[0267] 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.degree. C. 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.
[0268] This unique procedure simplifies the complexity of the
conventional coronary artery bypass surgery and makes the surgery
less invasive. Moreover, 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.
[0269] Thoracotomy and Aorotocoronary Bypass
[0270] 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.
[0271] 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 blockers and beta-blockers, and with hypothermia.
[0272] Creation of the Proximal Anastomosis
[0273] The ascending aorta is first palpated and examined by
transesophogeal 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 6 mm outer diameter) and may be placed
in the aorta to prevent narrowing at the proximal anastomosis.
[0274] This technique involves safe and simple placement of the
proximal anastomosis of the vein graft without clamping of the
aorta and without using 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).
[0275] 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.
[0276] Exposure of the Coronary Arteries and Creation of the Distal
Anastomosis
[0277] 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.
[0278] 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 patency
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.
[0279] This procedure is repeated until all the blocked vessels to
be revascularized are bypassed. After checking for bleeding, the
surgeon closes the chest.
[0280] The present invention is not to be limited in scope nor
restricted in form except by the claims appended hereto.
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