CA1075556A - Multipurpose cardiocirculatory assist cannula and method of use thereof - Google Patents

Abstract

MULTIPURPOSE CARDIOCIRCULATORY ASSIST CANNULA AND METHOD OF
USE THEREOF

ABSTRACT OF THE DISCLOSURE

A method and device for assisting cardiocirculation includes inserting a cannula in the axillary or subclavian artery, which cannula has associated therewith a blood pump, a balloon pump which responds to EKG signals, and a heart pacer which triggers the EKG and is capable of responding to and reversing ventricular extrasystoles, and maneuvering the cannula into the aorta and left ventricle. The device functions by directly unloading surplus blood from the left-ventricle of the heart, thereby reducing the work load of the heart so that it may in time recover from a serious if not critical insult.

Description

1~75556 The present invention relates to a cardiac assisting device and, more particularly, to a multipurpose cardiocir-culatory assist cannula.
The clinical management of myocardial failure and impending cardiogenic shock following acute ~yocardial in-farction remains one of the most challenging and important problems facing clinicians. Equally as important is the vexing problem of sudden cardiac dea~h associated with cardiac arrhythmia.
The prevention of such myocardial failure and cardiogenic shock rests upon the consideration of the patho-physiologic mechanism thereof. M~tabolic derangements pro-duced by myoeardi~l ischemia result in a profound deteriora- ;
tion of myocardial performance involving dyskinesia. There is a decrease of diastolic compliance o the myocardium as well as a diminished contractile potential. ~his leads to :,.j - . .
an increase of end-diastolic and left atrial pressures and volumes. The end results of this cycle is cardiogenic shock and death.
In many instances, coronary artery disease and/or arterial sclerotic heart disease in themselves must be con-sidered somewhat distinct from the terminal state or its causal relationship to any precipitating factors. The de-generative disease is a result of a progression of perhaps many years' duration. At some point in time, the heart sustains an insult to which it is incapable of adjusting or responding, let alone reversing the process by its own mechanism and power. Cardiocirculatory support and assist-ance, for whatever period, becomes critical if the system .

*

;' . .

~075S5~

is to be alLowed to correct the effects and maintain vital homeostatic processes.
There is still another factor which has played an important, though somewhat elusive role -~ namely, the question of sudden cardiac death resulting from the effects of uncontrolled and irreversible arrhythmia. Decreased myocardial perfusion resulting from coronary occlusive diseases i9 believed to be principally responsible for those conditions leading to myocardial catabolic derange-ments. Acidosis and electrolyte imbalance crea~e a hyper~
sensitive intrinsic conductive mechanism w lnerable to erratic triggering. The Pnd result is often ventricular extrasystoles followed by fatal arrhythmia.
Thus, a heart may be found which already suffers from some degree of degenerative disease of the myocardium and of the coronary arteries including interstitial fibrosis leading to decreased levels of myocardial perfusion. Up to this point and within rather critical lim~ts this heart is capable of carrying on its normal function and responding to increased demands of stress. However, for any number of reasons, at some point in time the scales are tipped and inadequate cardiac output results from the synergistic insult o~ decreased coronary perfusion coupled with and aggravated by a decrease in the contractile force of the heart. The decreased cardiac output precipitates a vaso-motor response leading to increased peripheral resistance.
This further aggravates the problem of inadequate cardiac return and of tissue perfusion leading to severe metabolic derangement and as a consequence vasomotor collapse~ thus ~3755S~

completing the syndrome of the picture of myocardial-circulatory failure.
Whatever triggers the above sequence of events, most investigators agree that the myocardium responding to a compromised circulation (insuffifiency of myocardial per-fusion) undergoes a somewhat rapid and devolutionary course leading to myocardial failure, cardiogenic shock and death. The other sequence of events is that of cardiac arrhythmia and sudden death.
Prior art cardiac assist pumps provide an intra-aortic occlusion balloon pumping system These devices are very important for providing intra-arterial cardiac assistance but are not designed, nor do they accomplish the improvement of myocardial revascularization or the in-crease of coronary collateral circulation. Furthermore, the presently known counterpulsation devices are based on the phase relationship of the cardiac cycle to the intra-aortic occlusion balloon. Thus, these devices are prone to failure if erratic triggering or cardiac arrhythmia occurs~
It is therefor an object of the present invention to provide a mul~i-purpose cardiocirculatory assist cannula whose capability extends beyond that of existing balloon catheters, and an improved method oftreating cardiovascula-tory ailments, to augment coronary perfusion, and to in-crease tissue perfusion.
It is a further object of the present invention to pace the left ven~ricle thereby counteracting the effects of arrhythmia crises and death while at the same time 1~755S~

ensuring proper phasing of the balloon counterpulsation.
These and other objects are accomplished by the present device which involves a cannula~ preferably hav-ing three functions, which may be inserted into the axil- -lary or subclavian arteries and fed through the aorta until the tip extends into the left ventricle. This can-cula (1) acts as a blood pump which withdraws blood from the left ventricle and reinfuses it into the coronary sinuses; (2) it acts as a balloon pump in the aorta to further decrease the workload of the heart; and (3) it acts as a heart pacer wh;ch supplies direct ventricular pacing.
Since the myocardium receives most of its blood flow during diastole, the reinfusion of blood via the can-nula during this period will increase coronary flow and hence myocardial perfusion pressure. Further, inflation of the balloon at this time augments this flow pressure relationship and hence is optionally effective in assist-ing the ischemic heart thereby reversing the serious im-pending catabolic-biochemical imbalance which oftentimes heralds,if not precipitates, arrhythmia. The phase rela-tionship is extremely important to the successful operation of counterpulsation balloon devices of whatever configura--tion. The present device is capable of dealing with the question by the simple expediency of controlling heart rate and the balloon in such a fashion so as to ensure the proper phasing of each cycle.
The further nature and advantages of the present invention will be more apparent from the following detailed , , .

~ ~ S 5~ 6 description taken in conjunction with the drawings where-in:
Fig. 1 is an elevational view of the multipurpose cardiocirculatory assist cannula of the present invention;
Fig. 2 is a partly broken away perspective view of the cannula of the present invention;
Fig. 3 is a cross-sectional view through line 3-3 of Fig. 2;
Fig. 4 is a cross-sectional view of another embodi-ment at a location similar to that of Fig. 3; and --Fig. 5 is a block diagram indicating the various subsystems necessary for the complete operation of the present device.
The device consists of a cannula 10 (Figs. 1 and 2) which may be fabricated from reinforced organo-silicon polymers such as Silastic (registered trademark) or other blood compatible m~terials, or at least coated with such a material. The proximal end of the cannula 10 consists of a nozzle 11 which may advantageously be made of Teflon *
(polytetrafluoroethylene). The nozzle 11 is designed to allow for quick connection to suitable drive means and consoles (Fig. 5), the nature of which will be clear to those having knowledge of the present field.
Surrounding the base of the nozzle 11 and the hous-ing 18 of the cannula is an outer housing 19. The outer housing 19 around the area at the base of the nozzle 11 is flanged outwardly in order to define an annular chamber 17 around the cannula housing 18. An inlet valve 12 leads through the outer housing 19 for attachment to the pneumatic * - Trade ~lark ' - ~ , ~ . . . .

drive of the balloon control for the balloon section 41 of the device lO. The pneumatic chamber 17 is preferably constructed with an airtight elastic recoil-type diaphragm 20 extending between the housing 18 and outer housing 19 below the inlet opening 12.
Extending distally from the pneumatic chamber 17 is a pneumatic conduit 13 between the housing 18 and the outer housing 19. The conduit 13 may be in the form of small tubes 38 which are held in place on the outside of the hous-ing 18 by outer housing 19 as seen in Fig. 3. In this em-bodiment the rigid material of the outer housing 19 which makes upthe wall of chamber 17 is molded to a more flexible material 37 at a point below the chamber 17, which flexible material 37 is laminated to the housing 18 around tubes 38.
The flexible material 37 is still considered a part of outer housing 19.
Alternatively, the outer housing 19 can remain rigid all the way to the balloon portion 41 in order to define an annular conduit 39 as seen in Fig. 4. The con-duit 13 empties directly into the balloon 14 which has been molded onto the outer surface of the cannula at approximately the midpoint thereof.
If diaphragm 20 were omitted it is apparent that the gas (preferably a low density gas such as C02) entering opening 12 would pass through chanber 17 and directly into conduit 13 and the balloon portion 41, thereby inflating the balloon 14. In the preferred embodiment, however, a predetermined pressure is sealed into the balloon 14, con-duit 13 and chamber 17 up to the diaphragm 20. Gas coming -~)75556 through opening 12 into the chamber 17 will depress elastic diaphragm 20 forcing inflation of the balloon 14. This arrangement prevents the direct flow of gas from the drive means to the balloon 14. Consequently, in the event of accidental rupture of the balloon 14, an excessive amount of gas will not be infused into the artery.
In addition to this safety feature, the use of an elastic diaphragm 20 in the gas chamber 17 will permit al-most instantaneous loading and unloading of the balloon 14 and will prevent the balloon 14 from completely collaps~ng becsuse of the preset pressure therewithin. The balloon 14 therefore will maintain a certain configuration in its deflated mode such that streamlined blood flow around the balloon 14 is provided, thereby avoiding further turbulence to the blood flow. It should be understood that the dia-phragm may be placed at any point between the cannula and the gas pump.
Be~ween the balloon 14 and the distal end of the cannula i9 a blood pump section 51. Here are located several mul~-fenestrated unidirectional elastic recoil out-let valves 15. When properly positioned these outlet valves 15 will come to lie with the sinus of Valsalva. The outer ; valves 15 are an integral part of a recoil band 21 which is laminated to the cannula housing 18 and is preferably constructed of the same material as the cannula hous~ng 18.
, A plurality of fenestrae 22 through ~he cannula housing 18 lead to outlet valves 15.
Between the ou~let valves 15 and the distal tip of the cannula lie multi-fenestrated inlet valves 16. The , :
~-, ~07S556 valves 16 are an integral part of a band 23 laminated to the inside diameter of the cannula and cover a plurality of fenestrae 24 through the ca~nula housing 18. The inlet valves 16 permit blood to be removed from the left ventricle to be subsequently reinfused through the outlet valves 15 into the coronary ostia.
The tip 25 of the cannula 10 is an obturator to permit passage of the device beyond the aortic valves. The tip is preferably made of a methyl methacrylate-type poly-mer such as Lucite or Plexiglas, possibly coated with a blood compatible material such as Silastic. A pressure transducer 26 may be attached to tip 25 to determine the diastolic pressure within the left ventricle. Suitable electrical leads (not shown) pass through the cannula to a suitable means to translate the signals from the trans-ducer 26.
A pacing electrode 27 is encapsulated within the housing 18 of the cannula 10 in a separate cable 28. The electrode 27 may be advanced independently of the tip of the cannula within cable 28 and may be freely rotated by means of a mechanism located in the area of the inlet nozzle 11. This mechanism is provided with a handle 29 and a plunger 30 which are illustrated schematically in Fig. 2. The tip of the electrode 31 may advantageously be formed in the shape of a grappling hook which opens when the electrode 27 is being extended and closes when it is withdrawn.
Thus the electrode tip 31 may be maneuvered into the optimal position within the ventricle for its pacing ~0755S6 function and then secured there by closing the hook onto a fiber of the ventricle wall. When the electrode 27 is eventually removed the fiber may be broken with no adverse effect. Since the electrQde 27 is made to operate inde-pendently of the cannula 10, once positioned the cannula 10 may be removed from the ventricle while the electrode 27 remains behind for the purpose of pacing the heart. Of course, handle 29 would have to be removed to permit this operation.
Referring to Fig. 5, the blood pump section 51 is -provided with suitable driving means 32 located in a con-sole near the patient. Blood is removed through the inlet valves 16 and reinfused through outlet valves 15. The pump and inner lumen may be primed wqth the patient's blood to begin the pumping operation. Preferably the device should ~, be capable of removing up to 20 cc of blood from the left ventricle and reinfusing the same quantity into the sinus of Valsalva.
, The balloon pump 41 is also provided with a driving means 33 located in the console. A pneumatic system 36 is connected thereto for inflAting the balloon 14 within a period of time commensurate with the length of time of the , cardiac cycle. The actual balloon pumping will be control-led by a delayed mode triggered by the heart pacer 34. The pacer 34 is connected to an electrocardiograph which in turn controls the phases of the blood pump drive means 32 , and balloon pump drive means 33.
; In operation the cannula 10 is inserted into any accessable artery leading to aorta, preferably the axillary or subclavian arteries, through a direct incision necessi-tating only a minor surgical procedure. It is then passed retrograde so that the tip 25 and the multifenestrated inlet portion 24 as well as the paclng electrode 27 come to lie below the aortic valve within the left ventricle. In this position the outflow tract 15 of the device will be within the sinus of Valsalva thus directing flow into both the left and right coronary orifices.
The balloon 14 will then lie in the transverse aortic arch distal to the carotid outflow tract. The tip of the electrode 31 is maneuvered to the most effective region of the left ventricle and is embedded in place. The most effective place is where the pacer has the best effect as shown by the electrocardiograph 35, which is determined by trial. Once positioned the device is ready to be put into operation.
First, the device can be made simply to unload the left ventricle directly, by withdrawing up to 30 ml of blood with each stroke and reinfusing this volume into the coronary sinuses durlng the diastolic phase of the cardiac cycle (pump systole).
Secondly, if it becomes necessary to decrease the workload of the heart further and increase coronary per~u-sion, the balloon 14 through a separate pneumatic conduit ~ -can be utilized. During cardiac diastole the resistance to flow in the vessels of the heart, i.e. the coronary ar-teries, is at a minimum. Inflation of the balloon 14 at th~s time increases the flow through the coronary arteries and pumps blood along the aorta toward the neck and head and toward the kidneys, liver, stomach and other organs.
Deflation of the balloon 14 at the end of cardiac diastole aids the heart by reducing the pressure in the aorta which the heart mMst normally pump against during cardiac systole.
This permits the heart to pump a large volume of blood with each contraction and also reduces the pressure in the left ventricle at the end of cardiac diastole.
Thirdly, to avoid problems of phase relationship of the device to the cardiac cycle, direct ventricular pacing is simultaneously started by means of the pacing electrode 27 located at the tip of the device.
In summary, the device is versatile enough so that during impending left ventricular failure secondary to myo-cardial infarction, it can directly unload the left vent-ricle, perfuse the coronary arteries, reduce the afterload resistance, and pace the left ventricle. As ventricular function improves and the heart is capable of providing a more adequate cardiac output, the cannula can be with-drawn until it lies within the ascending aorta, while the electrode tip remains behind to continue pacing the heart.
The operation of the blood pump at this time will be ter- -minated. The left ventricle, once recovered from initial failure may continue to require additional support by way of increased coronary circulation while reducing the after-load resistance and hence cardiac stroke work. The balloon 14 even after partial cannula withdrawal so that the tip of the device no longer protrudes through the aortic valve, will still be positioned within the aortic transverse arch distal to the carotid outflow tract. With proper pacing m7sss6 and positioning the cannula with the balloon can be used as a counterpulsating device.
In the preferred embodiment, the device measures 50 cm end-to-end with an outside diameter of about 1.5 cm and an inside diameter of .635 cm. The nozzle portion is approximately 4.5 cm in length. The balloon portion is approximately 25 cm from the nozzle. The balloon measures about 5 cm in length and can be inflated to contain about 15 to 20 ~c of gas. The pressure is preset within the dia-phragm to approximately half that. When fully inflated the balloon should have a sufficient diameter to occlude the aorta or about 2.5 cm. The outlet valves are located some 15-18 cm beyond the balloon and measure approximately 3 cm in length. The tip of the device is about 7 cm from the outlet valves of whîch the final 3 cm contain the multi-fenestrated inlet valve. The dimensions given above are by no means limitative but are meant to provide an example of workable dimensions for the normal sized human heart and circulatory system. Any dimensions which will permit passage of the cannula through the arteries and the posi-tioning of the various par~s in their operative positions are comprehended by the present invention.
It should be understood that the present invention may be fabricated by any presently available technique.
Furthermore, the materials disclosed for the various parts of the cannula are by no means limitative but any biocom-patible materials may be used. The pump system used may be any presently available system including pulsatile, non-pulsatile or centrifugal. The other electronic and 1~75S56 pneumatic components of the device are well known in the art individually and it is well within the skill of the art to select the proper components which will operate as described herein.

.

Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A multipurpose cardiocirculatory assist device for pumping blood directly from the left ventricle into the aorta past the aortic valve, comprising:
a hollow elongated cannula having a diameter sufficiently small for insertion into a human artery leading to the aorta, said cannula having a leading tip and a trailing end;
blood pump means to pump blood from the left ventricle during cardiac systole and into the aorta during cardiac diastole, including inlet valve means associated with that portion of the leading tip of said cannula dis-posed within the left ventricle during usage, for allowing blood to pass into said blood pump means, and outlet valve means associated with that portion of the leading tip of said cannula downstream from said inlet valve means which is disposed within the aorta during usage, for allowing blood to pass out of said blood pump means; and supplementary heart pumping assist means com-prising balloon pump means including a balloon connected to said cannula disposed downstream from said outlet valve means, said balloon pump means causing inflation of said balloon during cardiac diastole and deflation of said balloon during cardiac systole.

2. A cardiocirculatory assist device in accordance with Claim 1 further including electrode means at the leading tip of said cannula for pacing the heart.

3. A cardiocirculatory assist device in accordance with Claim 2, wherein said electrode means, blood pump means and supplementary heart pumping assist means include drive means connected thereto for supplying electrical pacing pulses to said electrode means, for driving said blood pump means, and for supplying gas for inflation and deflation-of said balloon pump means.

4. A cardiocirculatory assist device in accordance with Claim 1, wherein said blood pump means and said supple-mentary heart pumping assist means include drive means connected thereto for driving said blood pump means and for supplying gas for inflation and deflation of said balloon pump means.

5. A cardiocirculatory assist device in accordance with Claim 4, further including:
a chamber connected between said drive means and said balloon; and elastic diaphragm means connected within said chamber for preventing gas from said drive means from directly entering said balloon;
wherein the balloon side of said diaphragm is air tight and has a preset pressure therein whereby inflation of said balloon is dependent upon the position of said diaphragm means.

6. A cardiocirculatory assist device in accordance with claim 5, wherein said electrode means includes:
an electrode at the leading tip of said cannula; and a cable connected to said electrode and slidably housed in said cannula such that said electrode is movable axially and rotatably independently of said cannula.

7 A cardiocirculatory assist device in accordance with Claim 6, wherein said electrode includes securing means connected thereto for securing said electrode in place when in operation.

8. A cardiocirculatory assist device in accordance with claims 3, 5 or 7, wherein said drive means further in-cludes electrocardiograph means connected thereto for determining the proper periodicity of operation of said electrode means, blood pump means and supplementary heart pumping assist means.

9. A cardiocirculatory assist device in accordance with Claim 4, wherein said drive means further includes electro-cardiograph means connected thereto for determining the proper periodicity of operation of said blood pump means and said supplementary heart pumping assist means.

10. A multipurpose cardiocirculatory assist device for pumping blood directly from the left ventricle into the aorta past the aortic valve, comprising:
a hollow elongated cannula having a diameter suffi-ciently small for insertion into a human artery leading to the aorta, said cannula having a leading tip and a trailing end;
blood pump means to pump blood from the left ventricle during cardiac systole and into the aorta during cardiac diastole, including inlet valve means associated with that portion of the leading tip of said cannula disposed within the left ventricle during usage, for allowing blood to pass into said blood pump means, and outlet valve means associated with that portion of the leading tip of said cannula downstream from said inlet valve means which is disposed within the aorta during usage, for allowing blood to pass out of said blood pump means; and electrode means at the leading tip of said cannula for pacing the heart.