IMPLANTABLE CORONARY PERFUSION PUMP

Abstract: A cardiac pump assist system to move blood from large arteries, such as the aorta (32), to small arteries (34) where additional blood flow is needed. The pump assist system includes a shunt (21) from the aorta (32) or other convenient source of oxygenated blood to the coronary artery (34, 36) which is supplemented by a pump. The pump is preferably of the type employing a trained muscle wrap (14) around a fluid chamber (16).

Description: -i- IMPLANTABLE CORONARY PERFUSION PUMP FIELD OF THE INVENTION This invention relates to devices for increasing blood flow to small arteries. BACKGROUND OF THE INVENTION The partial or total blockage of small arteries, such as the coronary arteries providing blood to the heart, may result in ischemia and permanent tissue damage. Many therapies are used to improve coronary blood flow. For example, intraaortic balloon pumps (IABP) are used, in part, to augment coronary circulation by the principle of counter-pulsation. These are commonly used for up to 72 hours. Where more permanent solution is required to the blockage of the specific arteries, surgery can be performed to put in place a "bypass" to move blood around the occluded a . rtery portion. One very commonly used procedure of this type is the coronary artery bypass. Other methods are used for opening the occlusion, such as balloon angioplasty which uses an inflatable member to expand a blocked area. Another family of devices breaks up and removes the stenosis blocking the artery. This- is commonly known as atherectomy. This is performed by mechanical means as well as lasers. In cases where the coronary artery disease is more wide spread, it is difficult to treat the disease with these prior art methods. The- more diffuse the disease, the more difficult it is to use the existing therapies. It is well known in the art to use trained skeletal muscle as an implantable pump. For example, see United States Patent No. 4,411,268 to Cox which discloses muscle training methods. Such muscle pumps are well known in the area of cardiac assist for improving blood flow in the aorta as taught by Ray C.J. Chiu, M.D. in his book "Biomechanical Cardiac Assist". The concept of providing flow from the aorta to coronary arteries by a bypass is known. A side-by-side anastomosis of this type shunt to the various arteries is demonstrated in the prior art. These attempts have not, however, recognized the need for a pump to assist in providing blood to these coronary arteries. What is needed is a therapy that can provide blood flow through the coronary arteries generally so as to treat diffuse coronary artery problems and which has a capability, when desired, to provide assisted blood flow to the heart, especially during diastole, when the heart muscle around the diseased arteries is relaxed. SUMMARY OF THE INVENTION The present invention is a pump assist to move blood from large arteries, such as the aorta, to small arteries where additional blood flow is needed. The preferred embodiment includes a shunt from the aorta or other convenient source of oxygenated blood to the coronary artery which is supplemented by a pump. The pump is preferably of the type employing a trained muscle wrap around a fluid chamber. In one embodiment, a bladder pump is installed around the shunt with a fluid path leading to a sac inside the trained muscle. A muscle stimulator is attached to the heart for sensing heartbeats to synchronize the device. When assist of the coronaries is desired, the muscle stimulator will stimulate the trained muscle which will squeeze the fluid in the reservoir which in turn will increase pressure in the bladder to pump on the shunt. In other embodiments, the shunt can further be directed into the right atrium to use the atrium as a compliance chamber to avoid over pressure. The shunt may also preferably include a flow control element with or without a valve to prevent backflow in the shunt itself. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view of a heart employing the pump of the present invention. Fig. 2 is an alternative embodiment of the device of Fig. 1 showing use of a valve, a flow control element, and a compliance chamber. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As illustrated in Fig. 1, the device 10 includes a muscle stimulator 12, muscle wrap 14, fluid reservoir 16, fluid transmission tube 18, pump 20 including bladder pump 22 and shunt 21. Muscle stimulator 12 is of the type commonly used in prior art cardiac assist devices. Stimulator 12 is connected by line 24 to the heart so that stimulator 12 is capable of sensing heartbeats. Stimulator 12 is connected by line 26 to muscle 14 so that stimulator 12 can electronically stimulate muscle 14 for contraction. Apparatus 10 is shown connected to heart 30 on which is illustrated aorta 32 and coronary arteries including the Left Anterior Descending Artery (LAD) 34, and the Right Coronary Artery (RCA) 36. In this embodiment, shunt (graft) 21 is connected to provide blood from aorta 32 to artery 34 in a manner generally known in the. prior art. In this invention, however, pump 20 is in line in shunt 21 to assist in the transfer of blood. The programming physician selects the parameters of assist, choosing to stimulate muscle 14 preferably when the heart is in diastole. As is known in the prior art, one need not provide assist with each beat of the heart. The number of beats per assist can be varied. The ratio of beats to an assist is programmed in stimulator 12. Muscle stimulator 12 will stimulate tissue 14 at the programmed ratio. Tissue 14 will contract squeezing reservoir 16 and increasing pressure in line 18 into bladder 22. Bladder 22 will contract squeezing shunt 21. This will cause blood to flow from shunt 21 into coronary artery 34 bathing the heart tissue with oxygenated blood. This system augments the coronary artery circulation in a manner much more effectively than the prior art. Prior art cardiac assist devices only affect the coronary arteries remotely indirectly since they assist circulation throughout the whole body. The entire compliance capacity of the peripheral circulation system must be overcome in order to benefit the coronary arteries. This coronary pump of the present invention perfuses the coronary arteries directly. In the present invention, much smaller quantities of blood need to be moved in order to significantly help the coronary arteries. For example, the common coronary flow is approximately 300ml per minute. In one mode where the present invention moves only 1ml of blood per cardiac cycle, this would result in 60ml per minute. This is a 20% increase in blood flow to the coronary arteries. Obviously, this is a great increase compared to the relatively small effort by the pump. Since small amounts of blood need be transported, smaller muscle wraps can be employed than are required for the large aorta systems. An additional part of this invention is that times when the pump is not activated there is a natural flow through shunt 21 so there is always a flow of blood, even in times when there is no pump cycling. The embodiment of Fig. 2 shows additional features which augment the present invention. This illustration shows heart 40 having an aorta 42, right atrium 44, LAD 46 and RCA 48. Device 60 is shown to include stimulator 62, NAMES). Device 60 is shown to include stimulator 62, sensing line 64, stimulation line 66, muscle wrap 68, reservoir 70, fluid tube 72, shunt 76, valve 78, and flow control element 80. Pump 70 generally operates in the manner shown in the previous embodiment. In this embodiment- however, shunt 76 is directed into right atriu 44. Right atrium 44 acts as a compliance chamber to prevent over pressure and keep the system regulated. Flow control element 80 is used to control pressure. One example of a flow control device which is appropriate would be a Possis Perma-Flow graft. In the illustrated embodiment, shunt 76 is attached to artery 46 by side-by-side anastomosis in a manner known in the prior art. In other embodiments, shunt 76 is attached by side anastomosis to other arteries, such as artery 48. This embodiment further preferably includes valve 78 in shunt 76 which prevents backflow. For example, a valved conduit constructed in the manner of the Medtronic Hall aortic valved conduit prosthesis may be utilized. Thus, all pumping pressure will force blood down into the coronary arteries and prevent flow back into the aorta. This device bathes multiple coronary arteries in blood from the aorta while expending a minimum amount of energy in the pumping process. The tissue which most needs the blood for survival of the patient, the coronary tissue, receives the required blood in the most efficient manner possible. This reduces the need for large muscle wraps. What is claimed is:

Claims: II . CLAIMS 1. Apparatus for perfusing coronary arteries comprising: implantable shunt means for diverting arterial blood from a body source to a coronary artery; and pump means mounted for assisting flow of arterial blood in the shunt means. 2. The apparatus of claim 1, wherein the pump means comprises a trained muscle to apply pressure for assisting the flow of blood. 3. The apparatus of claim 1 further comprising: sensor means for sensing heart beats and for generating a pump signal based upon the sensing; and control means operably connected to pump means for activating the pump means upon receiving the pump signal. 4. The apparatus of claim 3 wherein the sensor determines that the heart is in diastole. 5. Blood diversion apparatus comprising: implantable shunt means for diverting blood from a source of said blood to a desired destination within the body; muscle powered augmentation means for assisting the flow of blood, the augmentation means comprising an active body muscle wrapped around a chamber which squeezes the chamber when the muscle is stimulated, to assist in the flow of blood; control means electrically connected to the muscle for stimulating the muscle. 6. The device of claim 4 further comprising; sensor means for determining when the heart is in diastole and for generating a diastole signal: and means within the control means for receiving the diastole signal for stimulating muscle when the heart is in diastole.

Inventors: CITRON PAUL, CITRON, PAUL
Applicants: MEDTRONIC INC, MEDTRONIC, INC.
Application year: 1990
Main classification: A61M1
IPC codes: A61M1