U.S. patent number RE35,352 [Application Number 08/588,791] was granted by the patent office on 1996-10-15 for method for intraluminally inducing cardioplegic arrest and catheter for use therein.
This patent grant is currently assigned to Heartport, Inc.. Invention is credited to William S. Peters.
United States Patent |
RE35,352 |
Peters |
October 15, 1996 |
Method for intraluminally inducing cardioplegic arrest and catheter
for use therein
Abstract
A process for inducing cardioplegic arrest of a heart in situ in
a patient's body, comprising maintaining the patient's systemic
circulation by peripheral cardiopulmonary by-pass, occluding the
ascending aorta through a percutaneously placed arterial balloon
catheter, venting the left side of the heart, and introducing a
cardioplegic agent into the coronary circulation. This procedure
readies the heart for a variety of surgical procedures that can be
performed percutaneously through lumina in the catheter. An aortic
catheter for use in the process is also described.
Inventors: |
Peters; William S. (Woodside,
CA) |
Assignee: |
Heartport, Inc. (Redwood City,
CA)
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Family
ID: |
25644382 |
Appl.
No.: |
08/588,791 |
Filed: |
January 19, 1996 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
159815 |
Nov 30, 1993 |
05433700 |
Jul 18, 1995 |
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Foreign Application Priority Data
Current U.S.
Class: |
604/6.14;
604/113; 604/28 |
Current CPC
Class: |
A61M
25/0026 (20130101); A61B 2018/00232 (20130101); A61B
2018/00261 (20130101); A61M 25/0023 (20130101); A61M
25/0032 (20130101); A61M 2025/028 (20130101); A61M
2025/1052 (20130101); A61M 2202/047 (20130101); A61M
2205/3344 (20130101); A61M 2205/3355 (20130101); A61M
2210/127 (20130101) |
Current International
Class: |
A61M
25/00 (20060101); A61M 037/00 () |
Field of
Search: |
;604/4,5,28,49,51-53,96-103,113 ;606/21,192,194 ;600/18
;128/898 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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218275 |
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Apr 1987 |
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EP |
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92/17118 |
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Oct 1992 |
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WO |
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Other References
Partington, M. T. "Studies of retrograde cardioplegia: II.
Advantages of antegrade/retrograde cardioplegia to optimize
distribution in jeopardized myocardium", J. Thorac Cardiovasc
Surgery, 1989, 97(4):613-622. .
Textbook of Surgery, 10th ed. (W. B. Saunders Company,
Philadelphia, 1972) pp. 2021-2023, 2114-2121. .
Ishizaka, M. "Myocardial protection by retrograde cardiac perfusion
with cold modified krebs solution through coronary sinus during
complete ischemic arrest for 120.", Ass. Thorac Surg (Japan),
25(12):1592-1601 (1977). .
Takahashi, M. "Retrograde coronary sinus perfusion for mycardial
protection in aortic valve surgery", Jpn Assoc Thorac Surg.
30(3):306-318 (1982). .
Gundry et al. "A comparison of retrograde cardiolegia versus
antegrad cardioplegia in the presence of coronary artery
obstruction" Ann Thorac Surg, 38(2):124-127 (1984). .
Lust et al. "Improvedprotection of chronically inflow-limited
myocardium with retrograde coronary sinus cardioplegia",
Circulation 78(5pt2)III217-223 (1988). .
Crooke et al. "Biventricular Distribution of Cold Blood
Cardioplegic Solution Administered by different retrograde
techniques", J. Thorac Cardiovasc Surg. 10240:631-636 (1991). .
Razi, "The challege of cacific aortitis", J. Card Surg 8:102-107
(1993). .
Ogawa et al. "Aortic arch reconstruction without aortic
cross-clamping using separate extra corporeal circulation", J. Jpn
Assoc Thorac Surg, 41(11):2185-2190 (1993). .
Buckberg, G. D. "Strategies and ogic of Cardioplegic Delivery to
Prevent, Avoid, and Reverse Ischemic and Reperfusion Damage", J.
Thorac Cardio Vasc Surg, 93:127-129 (1987). .
Yamaguchi, A. "A Case of a Reoperation Using a Balloon Catheter
with Blocked Pars Ascendes Aortae", Kyobu Geka, 42(11):961-964
(1991). .
Rossi, F. "Long-Term Cardiopulmonary Bypass by Peripheral
Cannulation in a Model of Total Heart Failure", J. Thorac Cardio
Vasc Surg, 100:914-921 (1990). .
Sabiston, D. C. Textbook of Surgery, 10th Ed, 2021-2023, 2114-2121,
(1972). .
Uchida et al. "Percutaneous Cardiomyotomy and Valvulotomy with
Angioscopic Guidance", American Heart J 121(4, Pt 1):1221-1224
(1991). .
Uchida et al., "Percutaneous Fiberoptic Angioscopy of the Cardiac
Valves", American Heart J, 121(6, part 1):1791-98 (1991). .
"Occlusion Balloon Catheters: Instructions for Use", Medi-Tech,
Boston Scientific Corporation, Rev. Mar. 1991. .
Cosgrove, D. M. "Management of the Calcified Aorta: An Alternative
Method of Occlusion" Ann Thorac Surg. 36:718-719 (1983). .
Foster and Threlkel "Proximal Control of Aorta with a Balloon
Catheter" Surg. Gynecology & Obstetrics, pp. 693-694 (1971).
.
Erah, Jr. and Stoney, Jr. "Balloon Catheter Occlusion of the
Ascending Aorta" Ann Thorac Surg. 35:560-561 (1983)..
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Primary Examiner: Yasko; John D.
Attorney, Agent or Firm: Townsend and Townsend and Crew
LLP
Parent Case Text
.Iadd.This application is a reissue of Ser. No. 08/159,815 filed
Nov 30, 1993 now U.S. Pat. No. 5,443,700. .Iaddend.
Claims
I claim:
1. A method for inducing cardioplegic arrest of a heart in situ in
a patient's body, comprising the steps of:
(a) maintaining systemic circulation with peripheral
cardiopulmonary by-pass;
(b) occluding at least one of the patient's vena cavae with an
inflatable cuff on a distal portion of at least one percutaneously
placed venous catheter to isolate a fight atrium of the heart from
at least a portion of the patient's venous system;
(c) occluding the ascending aorta through a percutaneously placed
arterial balloon catheter;
(d) introducing a cardioplegic agent into the coronary circulation;
and
(e) venting the heart through a percutaneously placed catheter.
2. A method as claimed in claim 1 in which the ascending aorta is
occluded by an arterial balloon catheter percutaneously placed
through one of the fernoral arteries.
3. A method as claimed in claim 2 wherein the cardioplegic agent is
introduced through a lumen in the arterial balloon catheter.
4. A method as claimed in claim 1 further comprising introducing a
fluid into the right atrium through a lumen in a percutaneous
venous catheter which opens between the two cuffs.
5. A method as claimed in claim 1 in which the percutaneous venous
catheter is introduced into the heart through a femoral vein.
6. A method as claimed in claim 1 in which the systemic circulation
is maintained through a cardiopulmonary by-pass that includes an
oxygenated blood return catheter introduced into one of the femoral
arteries.
7. A method as claimed in claim 1 wherein the vena cavae arc
occluded with two inflatable cuffs, each inflatable cuff being on a
separate percutaneously placed venous catheter.
8. A method as claimed in claim 1 wherein the vena cavae are
occluded with two inflatable cuffs both disposed on a single
percutaneously placed venous catheter.
9. A method as claimed in claim 1 further comprising withdrawing
venous blood from at least one vena cava through a lumen in at
least one of the percutaneously placed venous catheters and
directing the venous blood to the cardiopulmonary by-pass.
10. A method as claimed in claim 4 wherein the fluid comprises
saline.
11. A method as claimed in claim 1 wherein oxygenated blood is
returned from the cardiopulmonary bypass to the patient's arterial
system through a lumen in the arterial balloon catheter.
12. A method as claimed in claim 1 wherein the heart is vented by
withdrawing fluid through a lumen in the arterial balloon
catheter.
13. A method as claimed in claim 1 further comprising introducing
an instrument through a lumen in the arterial balloon catheter into
the patient's heart.
14. A method as claimed in claim 13 wherein the instrument
comprises a scope, the method further comprising visualizing the
heart with the scope.
15. A method as claimed in claim 13 wherein the instrument
comprises a cannula having a lumen, the method further comprising
venting fluids from the heart through the lumen in the cannula.
16. A method for inducing cardioplegic arrest of a heart in situ in
a patient's body, comprising the steps of:
(a) positioning a percutaneously placed venous catheter in at least
a portion of both of the patient's vena cavae and in a right atrium
of the heart;
(b) occluding a superior vena cavae with a first inflatable cuff on
a distal portion of the percutaneously placed venous catheter and
occluding an inferior vena cavae with a second inflatable cuff on a
distal portion of the percutaneously placed venous catheter to
isolate the heart from at least a portion of the patient's venous
system;
(c) withdrawing blood from the venous system through a lumen in the
venous catheter;
(d) oxygenating the blood withdrawn from the venous system;
(e) returning the oxygenated blood to the patient's arterial
system;
(f) occluding the ascending aorta through a percutaneously placed
arterial balloon catheter,
(g) introducing a cardioplegic agent into the coronary circulation;
and
(h) venting the heart through a percutaneously placed catheter.
17. A method for inducing cardioplegic arrest of a heart in situ in
a patient's body, comprising the steps of:
(a) maintaining systemic circulation with peripheral
cardiopulmonary bypass;
(b) isolating a fight atrium of the patient's heart from the
patient's venous system with at least one percultaneously placed
venous catheter;
(c) isolating a coronary vasculature from the patient's arterial
system with a percutaneously placed arterial balloon catheter;,
(d) introducing a cardioplegic agent into the coronary vasculature;
and
(e) venting fluid from the heart through a percutaneously placed
catheter.
Description
This application is a reissue of Ser. No. 08/159,815 filed Nov 30,
1993 now U.S. Pat. No. 5,443,700. .Iaddend.
FIELD OF THE INVENTION
The present invention relates to a method for inducing cardioplegic
arrest in a heart and to catheters for use in that method.
1. Background Art
The use of extracorporeal cardiopulmonary by-pass for cardiac
support has become well established. This use has, however,
involved median sternotomy or less commonly thoracotomy with all of
the trauma that necessarily accompanies such a major surgical
procedure.
The present invention contemplates, at least in its preferred
embodiments, the possibility of effective ascending aortic
occlusion, cardioplegia, venting, right heart deflation and topical
cooling-in association with extracorporeal cardiopulmonary by-pass
all without necessitating a median sternotomy or other thoracic
incision.
2. Disclosure of the Invention
In a first aspect the present invention consists in a method for
inducing cardioplegic arrest of a heart in situ in a patient's
body, comprising the steps of:
(a) maintaining systemic circulation with peripheral
cardiopulmonary by-pass;
(b) occluding the ascending aorta through a percutaneously placed
arterial balloon catheter;,
(c) introducing a cardioplegie agent into the coronary circulation;
and
(d) venting the left side of the heart.
The method according to the present invention may be carried out on
humans or other mammalian animals. The method is of particular
applicability in humans as it allows an alternative approach to
open heart surgery and the development of closed cardioscopic
surgery. The method according to the invention enables a
percutaneous by-pass system to be associated with cardioplegia,
venting and cooling of the heart which subverts the need for median
sternotomy. This may, in turn, reduce the complications of the
surgery.
The maintenance of the systemic circulation involves establishing a
cardiopulmonary by-pass. The blood may be drawn into the by-pass
merely by positioning a percutaneous catheter into the right atrium
and/or into one or both of the vena cavae through which venous
blood may be drawn from the heart into an extracorporeal pump
oxygenator. In more preferred embodiments of the invention a single
catheter with two inflatable cuffs, or two separate catheters, each
with an inflatable cuff are introduced into the vena cavae to
occlude them adjacent to their right atrial inlets. This allows
isolation of the fight atrium and allows blood to be drawn from the
vena cavae into the by-pass system. There is also preferably
provision for percutaneous communication via one catheter with the
right atrium to allow infusion of saline into the right atrium.
This infusion has the advantage that it allows the heart to be
cooled and improves visual acuity within the right heart allowing
direct cardioscopic examination and/or intervention.
The catheter used to decompress the right atrium and to draw blood
into the by-pass is preferably introduced through the femoral vein
by percutaneous puncture or direct cut down. If other than simple
venous drainage is required catheters with inflatable cuffs, as
described above, are placed preferably such that an inflatable cuff
of the cannula is positioned within each of the inferior
(suprahepatic) and superior vena cavae. There is preferably a lumen
in the cannula acting as a common blood outlet from the vena cavae
leading to the pump oxygenator. A separate lumen is preferably used
to infuse saline between the two inflated cuffs into the right
atrium. If, alternatively, separate catheters are used to occlude
each of the inferior and superior vena cavae then the cannula for
the inferior vena cavae is preferably introduced percutaneously
from the fernoral vein and that for the superior vena cavae is
introduced percutaneously through the jugular or subclavian
vein.
The ascending aorta is preferably occluded by a balloon catheter
introduced percutaneously through the femoral artery. This catheter
must carry adjacent its tip an inflatable cuff or balloon of
sufficient size that upon being inflated it is able to completely
occlude the ascending aorta. The length of the balloon should
preferably not be so long as to impede the flow of blood or other
solution to the coronary arteries or to the brachiocephalic, left
carotid or left subclavian arteries. A balloon length of about 40
mm and diameter of about 35 mm is suitable in humans. The balloon
is of a cylindrical shape to fully and evenly accommodate the lumen
of the ascending aorta. This maximises, the surface area contact
with the aorta, and allows for even distribution of occlusive
pressure.
The balloon of the catheter is preferably inflated with a saline
solution to avoid the possibility of introducing into the patient
an air embolism in the event that the balloon is ruptured. The
balloon should be inflated to a pressure sufficient to prevent
regurgitation of blood into the aortic root and to prevent
migration of the balloon into the root whilst not being so high as
to cause damage or dilation to the aortic wall. An intermediate
pressure of the order of 350 mmHg has been proven effective in
trials.
The aortic catheter is preferably introduced under fluoroscopic
guidance over a suitable guidewire. Transoesophageal
echocardiography can alternatively be used for positioning as has
been described with reference to the venous catheter. The catheter
may serve a number of separate functions and the number of lumina
in the catheter will depend upon how many of those functions the
catheter is to serve. The catheter can be used to introduce the
cardioplegic agent, normally in solution, into the aortic root via
one lumen. The luminal diameter will preferably be such that a flow
of the order of 250-500 ml/min of caxdioplegic solution can be
introduced into the aortic root under positive pressure to perfuse
adequately the heart by way of the coronary arteries. The same
lumen can, by applying negative pressure to the lumen from an
outside source, effectively vent the left heart of blood or other
solutions. It may also be desirable to introduce medical
instruments and/or a cardioscope into the heart through another
lumen in the catheter. The lumen should be of a diameter suitable
to pass a fibre-optic light camera of no greater than 3 mm
diameter. It is however, preferable that the diameter and
cross-sectional design of the internal lumina is such that the
external diameter of the catheter in its entirety is small enough
to allow its introduction into the adult femoral artery by either
percutaneous puncture or direct cut-down.
The oxygenated blood returning to the body from the by-pass system
may be conveyed into the aorta from another lumen in the cannula
carrying the balloon. In this case the returning blood is
preferably discharged from the catheter in the external iliac
artery. In another embodiment of the invention, and in order to
reduce the diameter of the catheter carring the balloon, a separate
arterial catheter of known type may be used to return blood to the
patient from the by-pass system. In this case a short catheter is
positioned in the other femoral artery to provide systemic arterial
blood from the bypass system. The control end of the catheter, i.e.
that end that remains outside of the body, should have separate
ports of attachment for the lumina. The catheter length should be
approximately 900 mm for use in humans.
The cardioplegic agent may be any of the known materials previously
known to be useful, or in the future found to be useful, as
cardioplegic agents. The agent is preferably infused as a solution
into the aortic root through one of the lumina of the aortic
catheter.
In another aspect the present invention consists in a catheter for
use in occluding the ascending aorta comprising an elongate tube
having one or more continuous lumina along its length, an
inflatable cuff is disposed about the tube adjacent one end
thereof, the cuff being of such a size that upon being inflated it
is able to occlude the ascending aorta of a patient.
The catheter and method according to the present invention can be
used to induce cardioplegic arrest and may be used in a number of
surgical procedures. These include the following:
1. Coronary artery revascularisation such as:
(a) angioscopic laser introduction or angioscopic balloon
angioplasty catheter into the coronary arteries via one lumen of
the aortic catheter, or
(b) thoraco dissection of one or both of the mammary arteries with
revascularisation achieved by distal anastomoses of the internal
mammary arteries to coronary arteries via a small left anterior
thoracotomy.
2Secundum-type arterial septal defect repair such as by:
(a) "Closed" cardioscopic closure, or
(b) Closure as an "open" procedure via a mini-right
thoracotomy.
3. Sinus venosus defect repairs similar to 2 above.
4. Infundibular stenosis relief by cardioscopie techniques.
5. Pulmonary valvular stenosis relief by cardioscopic
techniques.
6. Mitral valve surgery via a small right thoracotomy.
7. Aortic stenosis relief by the introduction of instrumentation
via a lumen in the aortic catheter into the aortic root.
8. Left ventricular aneurysm repair via a small left anterior
thoracotomy.
BRIEF DESCRIPTION OF THE DRAWINGS
Hereinafter given by way of example are preferred embodiments of
the present invention described with reference to the accompanying
drawings in which:
FIG. 1 is a schematic partly cut-away representation of a patients
heart having percutaneous catheters placed therein for carrying out
the method according to the present invention;
FIG. 2 is a similar view to FIG. 1 showing the aortic catheter in
position but including an angioscope and a left ventricular venting
cannula introduced into the aortic root and left ventricle
respectively, via separate lumina within the aortic catheter;
FIG. 3 is a front elevational view of part of the vascular system
of a patient showing, inter alia, the aortic balloon catheter
positioned in the ascending aorta via the femoral artery;
FIG. 4 is a side elevational view of the control end of the aortic
catheter according to the present invention;
FIG. 5 is a partly cut away side elevational view of the balloon
end of the catheter of FIG. 4 in an inflated condition;
FIG. 6a is a cross-sectional view of the catheter of FIG. 4
intermediate the control end and the balloon end;
FIG. 6b is an alternative cross-sectional arrangement of the lumina
in the catheter of FIG. 4;
FIG. 7 is a cross-sectional view through the balloon end of the
catheter of FIG. 4;
FIGS. 8a and 8b show schematically two alternative arrangements to
the catheter shown in FIG. 4;
FIGS. 9a and 9b show schematically two alternative catheter
arrangements for the isolation of the right atrium and venous
drainage.
BEST MODE OF CARRYING OUT THE INVENTION
The heart 10 of FIGS. 1 and 2 is positioned in the living body of a
patient and is accessed percutaneously.
In order to induce cardioplegia in the heart while maintaining the
patient it is necessary to divert the patients blood circulation
through an extracorporeal cardiopulmonary by-pass system. This is
achieved by isolating the heart 10 on both the venous and arterial
sides using appropriate percutaneously inserted venous catheter 11,
aortic balloon catheter 12, and if this catheter 12 doesn't have
provision for arterial blood return, arterial catheter 39 (see FIG.
3). The venous outflow and arterial inflow lumina of the catheters
11 and 12 of the by-pass system are of sufficient cross sectional
area to achieve standard blood flows to maintain the patient's
systemic circulation during the period of extracorporeal
circulation.
In the case of the use of a single venous double-ballooned catheter
11, as is shown in FIG. 1, the catheter 11 is inserted through the
fernoral vein preferably. A suitable guide wire is initially
inserted and the catheter 11 is then introduced in known manner
under fluoroscopic guidance. The catheter 11 includes a pair of
separately inflatable balloons 14 and 15 each connected to a
balloon inflation control device (not shown) through suitable
lumina in the catheter 11. The balloon 14 is adapted to occlude the
superior vena cavae 16 while the balloon 15 is adapted to occlude
the suprahepatic inferior vena cavae I7. A blood withdrawal lumen
in the catheter 11 has an inlet orifice 18 flush with the balloon
14, to avoid venous collapse during blood flow into the catheter
11, and a series of inlet slots 19 in the inferior vena cavae.
Blood drawn into the inlets 18 and 19 enter a common single lumen.
Blood drawn into the by-pass system through the catheter 11 is
oxygenated and returned to the patient in a manner which will be
hereinafter described.
A separate lumen in the catheter 11 opens into the right atrium 22
through aperture 21 to allow evacuation of blood from the right
heart and the infusion of saline to induce topical cooling and/or
to improve visual acuity within the right heart.
In use, after the catheter 11 has been positioned the balloons may
be inflated or deflated to vary the rate of venous return to the
right atrium 22 and therefore the degree of decompression of the
left heart. Venous drainage may be effected by gravitational
drainage or by applying a degree of negative pressure to assist
flow into the pump oxygenator. It will be appreciated that the
distance between the balloons 14 and 15 will need to be correct for
a given patient and this may be assessed by X-ray examination to
allow selection of an appropriately sized catheter. Alternatively
separate catheters 11b and 11c could be used, as is shown in FIG.
9a, for the inferior and superior vena cavae. The cannula 11b being
introduced as has been described above and the cannula 11c being
introduced through the jugular or subclavian vein. It will also be
appreciated that for simple operations not requiring complete
occlusion of the right atrium it is possible to merely insert a
simple catheter 11 into the right atrium to draw blood into the
by-pass system as is seen in FIG. 2. Positioning under fluoroscopic
guidance is not essential in this case.
The catheter 12 is positioned in the manner described above with
its free end located in the ascending aorta 23. The catheter 12 is
so positioned by insertion preferably through the femoral artery 24
and via the descending aorta 25 as is seen in FIG. 3.
If desired a fluoroscopic dye may be introduced into the aortic
root 26 through the catheter 12 for accurate positioning of the tip
of the catheter 12 relative to the aortic root 26 and the coronary
ostia.
The catheter 12 carries at its free end a balloon 27. The balloon
27 is arranged to be inflated with saline from an inflation control
device 23 of known type through a lumen in the catheter 12. The
device 28 is fired with a pressure gauge 29 to allow the operator
to control the inflation of the balloon 27. The pressure of the
fully inflated balloon 27 should be of the order of 350 mmHg so as
to be sufficient to effectively occlude the aorta and to prevent
the balloon moving while not being so great as to cause damage to
the aortic wall. The balloon 27 should have a maximum diameter
sufficient to occlude the aorta and for this purpose the maximum
diameter should be about 35 mm. The balloon 27 should have a length
of about 40 mm so as not to be so long as to occlude or impede
blood flow to the coronary arteries on to the brachiocephalic,
subclavian or carotid arteries. If necessary in any given patient
the required length and diameter of the balloon may be determined
by angiographic, X-ray examination or echocardiography and an
appropriately sized catheter selected on that basis.
The balloon 27 is preferably connected to the lumen 32 through
which it is inflated at the end of the balloon 27 distal to the tip
of the catheter 12 through orifice 31 (see FIG. 5). This allows the
tip of the catheter to contain fewer lumina than the remainder of
the catheter. Accommodation of the deflated balloon around the tip
of the catheter is thus possible without adding to the diameter of
the tip as compared with the rest of the catheter 12.
The catheter 12 includes a plurality of lumina (see FIGS. 6 and 7).
In addition to the balloon inflation lumen 32 there is at least a
single venting/cardioplegia lumen 33 of circular cross-section.
There may be a separate and extra circular lumen 34 for
instrumentation. If two lumens are present the venting/cardioplegia
lumen may be circular or crescent shaped in cross-section (FIG. 6a,
6b). The diameter of the various lumina should be as small as
practicable commensurate with the intended use. In addition there
may be a continuous lumen 35 through which arterial blood is
returned from the by-pass. This may flow out of the catheter 11
through an orifice in the region of the external iliac artery. In
alternative embodiments of the invention such as shown in FIGS. 3
and 8 the arterial return lumen 35 may comprise its own catheter 39
of known type introduced into the other femoral artery or some
other suitable artery.
The control end of the catheter 12, illustrated in FIG. 4, has a
plurality of ports of attachment 40, 41, 42 for each of the lumina
32, 33, 34, respectively. Inflation control device 18 and pressure
gauge 19 may be connected to port 40 to allow the operator to
control inflation of balloon 27.
In use the catheter 11 is introduced percutaneously by puncture or
cutdown as has been described and once blood flow through the
by-pass is established (including systemic cooling) flows are
reduced and the balloon 27 is inflated. Flows are then returned to
the operating levels and a suitable cardioplegic agent is
introduced into the aortic root. Once the full volume of
cardioplegic agent has been given and cardiac arrest achieved, the
lumen is then used to vent the heart. The heart may then be
operated on or examined by insertion of instrumentation 37 such as
a cardioscope or a laser into the heart through the lumen 34 or
through atrial trocars. Alternatively, with the heart on by-pass as
described above the heart can be approached by an open method by an
incision other than median sternotomy. Venting of the left
ventricle may be effected by providing an extended cannula 38
projecting from lumen 33 into the left ventricle (see FIG. 2) or by
simply applying negative pressure to the venting lumen 33 of the
aortic catheter. To reverse cardioplegic arrest the body is
rewarmed and the balloon 17 deflated. Aortic blood is thus allowed
to perfuse the heart. Whilst the body remaim supported by
peripheral cardiopulmonary bypass, the return of the heart rhythm
is awaited. External defibrillation may be necessary. Weaning from
by-pass is then completed in a routine fashion.
* * * * *