Artificial heart pump or assist

Abstract

An implantable artificial heart pump or heart assist for providing or enhancing a controlled cyclic blood flow through an artery, the pump including a tubular section secured between adjacent ends of a severed artery forming a continuous blood flow passage, and having a plurality of axially spaced but adjacent sleeves encircling this section. The sleeves are sequentially constricted about the tubular section to provide alternately pumping and suction upon the blood flowing through the section, the sleeves being energized by high and low pressure working fluid from an external or implantable power source. Where the power source is an implantable Stirling engine, pressure variations are available from the gas working space, or from an oil pump in the crankcase, or from a compressor driven by the engine.

Description

BACKGROUND OF THE INVENTION

Existing artifical heart pumps generally comprise substitute or assist mechanisms which include one or more valves which are cyclically opened and closed, in response to either the pressure build-up of blood on the valve or to a timing device separate from the valve. In all of the heart pumps having valves there are necessarily stagnation points in the blood flow path; namely a part of the flow channel where a portion of the blood flow is halted from flowing for a prolonged period of time, and in its worst case where a portion of the blood flow is permanently halted. Blood in the vicinity of stagnation points has a tendency to coagulate, deposit, or build up on the adjacent valve surfaces, which impedes subsequent flow of blood past said surfaces. Such blood clots may eventually break loose and cause fatal injury to the patient.

A further problem area in typical heart assist devices utilizing valves is that some constituents of the blood may be damaged due to excessive pressure, velocity and shear forces occurring when a valve is being closed and the pressure drop through the reduced-size flow passage is substantially increased over normal values.

The new invention is a mechanism for use in a human or animal body to improve blood flow, the mechanism having structure and geometry which avoids or at least reduces significantly the above-mentioned problems.

SUMMARY OF THE NEW INVENTION

The invention is a heart pump that may substitute for or assist an existing human heart in its operation of pumping blood through arteries. The new device is an implantable pump in communication with the high and low pressure variations occurring, in its preferred embodiment, in a pressure source such as an implantable Stirling or Rankin engine, using the gas working space, or oil pump, or the high and low pressure variations of a compressor driven by the engine. The new device includes a tubular section that is joined to and between the severed ends of an artery, such that the blood will have a continuous and substantially uninterrupted flow path through the artery and the tube-section. At least two and preferably three sleeves axially spaced apart but adjacent, encircle this section. Each sleeve has its diameter cyclically contracted and enlarged about the tube, such that the bore or flow passage through the tube is cyclically (a) constricted to reduce or stop blood flow and then (b) enlarged to permit normal flow therethrough. When all three sleeves are subjected to the high pressure, all would be expanded, and the tube and artery continuous therewith would fill with blood. In operation the first sleeve (which would be designated as in the upstream position) is constricted; this is followed by the second sleeve being constricted while the first remains constricted, and then the third is constricted while the first and second remain constricted. This tends to force the blood from the first into the second, then into the third, and finally out of all of the sleeve areas and downstream. Still later, the two sleeves at the downstream end are kept closed to prevent backflow while the first sleeve is opened such that a new charge of blood can begin to enter the pump mechanism. Then the second is also opened, followed by the third, such that all are open again, this sequence functioning at least in part as a suction stage.

One possible sleeve configuration comprises a tubular member formed into a ring that has one end sealed and the other end connected to a source of fluid that is supplied either at a low or a high relative pressure. The ring has a normal diameter, and application of the high pressure causes the ring to uncoil and enlarge its diameter; the ring's resilience will return it to its normal diameter when pressure is reduced or discontinued. Alternatively, the sleeves (rings) could be designed to contract or reduce in diametral dimension upon the application of high fluid pressure, with their resilience returning them to a normal enlarged diameter.

A valve or timing mechanism situated between the source of fluid and the sleeves, will control the selection of sleeves to be pressurized to alter the diameter of each relative to the others. Since these sleeves contact and operate on the outer surface of the tube, they are entirely external of the actual blood flow, which overcomes numerous disadvantages in prior art devices, as discussed below. Another variation of the above invention would be to leave the artery unsevered, to omit the tube section, and position the sleeves directly upon the outer surface of the artery.

The pump mechanism of this invention has a variety of significant advantages over prior art pumps and heart assists. First, there are no stagnation points for the blood flow throughout the entire mechanism; the mechanism is in fact totally external of the artery, such that the blood flows through a substantially clear and unobstructed tubular portion of the artery that is free of valves or other obstacles found in other pumps. As mentioned above, this stagnation problem has been significant, and to avoid it is a considerable benefit and achievement. Second, the pump mechanism is extremely uncomplicated and inexpensive, in comprising simple sleeves which change dimension but otherwise do not move and do not have to mate with other parts, and do not have close tolerances, and do not have seals, bearings, and other parts which can wear out. The sleeves will merely expand and constrict, and there are numerous materials available including metals, plastics and rubber which have proven ability to flex thousands or millions of cycles without deteriorating excessively or losing their necessary characteristics. Also, the sleeves would be secured together in some manner to maintain their axial spacing, such that the constriction of one sleeve effecting the blood flow therein would not be remote and unrelated to the application of pressure upon blood in the adjacent sections of the artery. The number of sleeves can be increased to provide a smoother flow of the blood, however a minimum number of two sleeves is required, and presumably three would function reasonably well.

In order to operate a pump of this type, it is necessary to have a source of both high and low pressure gas or liquid working fluid. An implantable Stirling engine has a gas working space and also a lubricating oil pump that experience such appropriate high and low pressure differentials; this gas space or the oil pump can be connected directly to the sleeves through a valve which automatically selects the suitable pressure level for each sleeve. Alternatively a Stirling or other implantable power source can drive a compressor whose high and low pressure ducts are fed to the sleeves via a valve. Stirling engines can operate over a long, extended period of time, by using an isotope heat source, and can run maintenance-and-adjustment-free. The sleeves could be timed to operate at the same rate as the compressor and/or the engine, or could cycle at a multiple or fraction of the valve speed.

A preferred embodiment of this invention is disclosed with reference to the drawings described below.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic diagram of heart assist system including an artery pump and a Stirling engine providing high and low working gas pressure.

FIG. 2 is schematic diagram of another embodiment of a system similar to FIG. 1, wherein a Stirling engine drives a compressor which provides the high and low pressures.

FIG. 3 is a schematic diagram of another embodiment similar to FIGS. 1 and 2, with the oil pump in the crankcase providing high and low pressures.

FIG. 4 is a partial elevation view of the pump of the new invention.

FIG. 5 is a sectional view taken along line 5--5 of FIG. 4.

FIG. 6 is a sectional view taken along line 6--6 of FIG. 4.

FIG. 7 is a schematic view showing the pumping and suction cycles of the device of FIG. 4.

FIG. 8 is a pressure vs time diagram showing six periods for a complete (FIG. 7) cycle of the FIG. 4 embodiment.

FIG. 9 is a partial elevation view in section of a second embodiment of the invention with a center core.

FIG. 10 is a sectional view of another embodiment similar to FIG. 9.

FIG. 11 is an end view taken along line 11--11 in FIG. 10.

FIG. 12 is a sectional view taken along line 12--12 in FIG. 10.

FIG. 13 is a diagrammatic view of a rotary control valve to selectively provide high and low pressure to the three sleeves in selective sequence of the device in FIGS. 4, 9 and 10.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention as a whole implantable system is shown in FIG. 1 where a Stirling engine 1 has a working or compression space that experiences high and low pressures available at ports 2 and 3 respectively, which are connected via ducts and corresponding high and low pressure buffer tanks h.sub.1 and h.sub.2 to a valve 4; one embodiment of this valve is shown in detail in FIG. 13. The valve selectively feeds high and low pressure to sleeves 5, 6, and 7 which encircle tube 8 connected between the severed ends 9 and 9' of an artery as a continuous blood flow duct, the valve being controlled by a connection 4' with engine. The sleeves and tube 8 together form the pump component 10 which pumps blood in the direction of the arrows. the operation of the pump and valve components will be described in detail below, while the operation of a Stirling engine is known and described in numerous publications such as U.S. Pat. Nos. 3,443,079, 2,885,855, 3,318,089 and 3,318,100.

FIG. 2 shows schematically a variation from FIG. 1 with similar components given the same reference numerals but modified, for example, from 1 to 1a. Accordingly a Stirling engine 1a has a mechanical or hydraulic power output 1b that drives compressor 1c which has a low pressure connection 3a feeding a buffer tank 3b to valve 4a, and a high pressure connection 2a which also feeds valve 4a via a buffer tank 1d for storing high pressure working fluid. The valve 4a automatically feeds the appropriate high and low pressure fluid to sleeves 5a, 6a and 7a about tube 8a of pump 10a.

FIG. 3 shows a third variation wherein the heart assist system comprises the lubricating oil pump 1e in the crankcase 1f of Stirling engine 1g. High pressure oil is fed to a high pressure buffer tank 3c and then to the control valve 4b for sleeves 5b, 6b, and 7b. A spring bellows expander may be situated inside of the buffer tank (see FIG. 3a) will help maintain a generally constant tank pressure when valve 4a opens and draws fluid from the tank. The spring-loaded or gas-pressure biased bellows in the tank would maintain an oil supply pressure substantially constant. Where a Stirling engine is utilized to provide directly, or indirectly the high and low pressure fluid, a radioactive isotope capsule is suggested to supply heat for long-term operation of the engine.

The pump 10 of FIG. 1 is shown in FIG. 4 where a section of tubing 10c is surrounded by three sleeves 11, 12 and 13. The direction of flow is from left to right as indicated by arrow 14, and the tube has a nominal undisturbed diameter d.sub. 1, as compared to a constricted diameter d.sub. 2 resulting from reducing the diameter of the sleeves. FIG. 5 shows the tube 10c and sleeve 11 in an expanded state, and FIG. 6 shows the tube and sleeve 13 or 12 in a contracted state. Each sleeve is normally constricted as in FIG. 6 and is expanded when a fluid pressure is applied to the internal chamber of the hollow sleeve causing it to expand as indicated in FIG. 5.

The operation of the above pumping device is shown in six stages symbolically in FIG. 7 and diagrammatically in FIG. 8. In stage 1 of FIG. 7 the first sleeve is expanded while the second and third sleeves are constricted; this corresponds to the chart of FIG. 8 which shows sleeve 1 at high pressure, namely that it is expanded and blood can fill the space it encloses, in contrast to sleeves 2 and 3 which are indicated to be energized with low fluid pressure or that they are constricted resulting in greater resistance to the blood flow. Stage 2 of FIG. 7 shows that the first two sleeves are expanded while the third remains constricted; FIG. 8 in stage 2, corresponds by showing sleeves 1 and 2 energized with high fluid pressure while sleeve 3 is still at low pressure. Stage 3 in FIG. 6 shows all three sections to be expanded such that all three sleeves are being energized with high pressure fluid, and this corresponds to FIG. 8 stage 3 where all three sleeves are indicated to be at high pressure. Stage 4 in FIG. 7 shows the first section to be constricted by corresponding action of sleeve 1; FIG. 8 shows the corresponding diagram whereby only sleeve 1 is constricted, whereas sleeves 2 and 3 remain expanded, that is, subjected to high energizing fluid pressure. Stage 5 shows that the first sleeve has remained constricted and the second is constricted thus forcing net flow in the direction of the arrow to the right out through section 3. And, stage 6 shows all sleeves to be constricted thus forcing the net flow from section 3 further outward, while the first two closed sections prevent to some extent the fluid from moving backward. As the cycle beings again, we return to stage 1 where section 1 is opened while sections 2 and 3 remain closed. This permits fluid to enter section 1 while it substantially prevents fluid from flowing backwards into sections 2 and 3. Next, section 2 is opened which allows more net fluid flow to move to the right into the pump and in fact draws the fluid in because resilience of the section causes it to open creating a partial vacuum therein. And, finally, all three sections are opened in stage 3. Again in stage 4 the first section is closed which forces net fluid flow toward the right in the direction of the arrows in FIG. 7.

FIGS. 7 and 8 demonstrate a pumping action comprising a suction or priming cycle in stages 1, 2 and 3, and a pumping forcing cycle in stages 4, 5, and 6. It would be possible to use only two sleeves but the efficiency of the pump would be considerably reduced.

FIG. 9 shows another embodiment of the invention which is similar to but modified from that in FIG. 4. The pumping device 15 is in a housing 16 with a section of tubing 17 axially disposed in a housing. The entire pumping device is to be attached to the severed ends 18, 19 of an artery along junction lines 18' and 19'. The three sleeves for producing the pumping action are shown as 20, 21 and 22 with each being connected to a fluid port 20', 21' and 22' which feeds energizing fluid under pressure to the sleeves for expanding same according to the method earlier described.

Significantly different in the FIG. 9 embodiment from FIG. 4, is center core 23 which is fixedly positioned in the center or thereabouts of the tube section 17; FIG. 11 shows streamlined webs 29 at the entrance and exit of the tube for supporting the core element. Sleeve 20 as shown constricts the flexible tube 17, until it closes substantially or completely about core 23; subsequent closing of sleeve 21 would force fluid flow in the direction to the right, past sleeve 22. It should be obvious that the presence of the core allows the constricted tube to nearly completely close off flow in contrast to the prior embodiment where there is no core and the constriction of the first sleeve would only tend to restrict flow, but obviously there would be considerable leakage backward because the passage within the tube remains open. It is contemplated that this pump device of FIG. 9 would be embedded as a unit within the body while the two ends thereof are attached to the severed artery at 19 and 18, and the fluid ports 20', 21' and 22' would be attached to pressurized fluid means to be discussed later.

FIG. 10 shows a more detailed view of an embodiment similar to that of FIG. 9. The sleeves 24, 25 and 26 are indicated as coil sections of hollow tubing each connected to a port through which pressurized fluid is directed. It is necessary to support the center core 27 centrally of tubing 28, and this is done by webs 29 shown in FIG. 11 which is a right end view of FIG. 10. The webs are thin and streamlined and represent minimum obstruction to the flow of blood in the annular space 29' about the center core and within tube section 28. FIG. 12 includes a sectional view of the port 30 for energizing a sleeve 24.

With any of the above-described pump components it is necessary to provide both high and low pressure fluid to the different sleeves in a proper sequence. This may be accomplished with a compressor or other means to develop high and low pressure in a liquid or a gas, and a valve such as rotary valve means according to FIG. 13 which directs fluid flow to appropriate sleeves. This valve has outlets P.sub.1, P.sub.2, P.sub.3, connected respectively to sleeves 24, 25, and 26 of FIG. 10, or to three sleeves of any other embodiment; it also has a low pressure inlet P.sub.L, and a high pressure inlet P.sub.H. During stage 1 for example, with FIG. 10, we will need a high pressure at sleeve 24 and low pressure at sleeves 25 and 26. The inner rotor permits communication of high pressure inlet P.sub.H with outlet P.sub.1, and low pressure inlet P.sub.L with outlets P.sub.2 and P.sub.3.

The exit ports are positioned around the housing of the valve such that rotation of the rotor exposes appropriate exit ports at the correct timing to provide a cyclic pressure variation for the three sleeves, or any number that is chosen, according to FIGS. 7 and 8.

It should be noted that the section of tubing i.e. 17 in FIG. 9, used in any of the pumps, preferably should have resiliency, such that it tends to hold its open shape; this eliminates direct outward radial pulling contact between the sleeve and section of the tube. Furthermore, each sleeve is resilient member which tends to hold its constricted shape at low energizing pressure. Thus, when a sleeve is energized by having a pressure applied to its hollow inner chamber, and said sleeve expands, the portion of the tube adjacent to the sleeve will expand on its own due to its own resiliency. Obviously, it would be possible to reverse these features such that the sleeve would have a normal expanded condition and that the application of fluid pressure would cause it to contract; then the tubular section within the sleeves would also have a normal open position with its resilience tending to maintain it that way; when pressure to the sleeve was reduced or relaxed, the sleeve and tube therein would automatically open to full diameter.

The opening of the first and second sections of the tube while the third section remains closed, acts as a suction or priming phase of the device, as the sleeve creates a greater volume and a partial vacuum such that blood will flow into these open sections mainly in the pumping direction; and during later phases of the cycle the blood will be pumped out mainly in the same direction.

If a gas rather than a liquid, is used to pressurize the sleeves, then dry friction seals (made from a plastic sold under the trademark Rulon) might be necessary in the valve mechanism. However, if a liquid such as oil is used as the energizing fluid, then the sealing requirements are greatly reduced, and metal surfaces moving in close proximity could fulfill the sealing function satisfactorily. The valve shown in FIG. 13 can be designed to control the flow to as many sleeves as desired, except that the diameter of the valve would increase as the number of flow connections increased. In general, if the pump has "N" number of sleeves, then it would have to have "N" number of flow outlets, and the angle ".THETA." in the valve according to FIG. 13 would be .pi./N radians. When one or more sleeves constrict the central tube, wrinkles in the constricted portion can be avoided by axially fixing the opposite ends of the tube; then the constricted part of the tube is also stretched lengthwise, and will not experience compression on bending.

The structures shown in these drawings are merely preferred embodiments for practising the invention, these structures being merely representative of the invention with no intention that the scope of the invention be limited to their configurations.

Claims

What is claimed is:

1. An implantable heart pump for pumping and controlling the flow of blood through an artery which is severable to expose two adjacent ends to accommodate the pump therebetween, this pump being operable with first and second sources of high and low pressure fluid respectively, the pump comprising a tube securable between said severed ends of said artery to form a continuous blood flow passage, at least two sleeves each having a generally cylindrical bore at least partially surrounding and contacting said tube, the sleeves being axially spaced apart but adjacent to each other, a core element formed as a rod fixedly positioned generally centrally within the bore of said tube and adjacent the inner surface thereof, the tube having a bore diameter that is variable between large and small, each sleeve being responsive to a pressure change whereby its diameter is variable between large and small corresponding to said tube bore diameters, and valve means for communicating selectively said high and low pressure sources to said sleeves, whereby each sleeve periodically has

a. a small diameter for constricting the tube to have a small bore diameter at the area of the tube adjacent said sleeve, and

b. a large diameter permitting a corresponding large bore diameter of said tube with the tubes inner surface at that area being urged closely against said core to prevent blood flow in that area, the valve providing a predetermined sequence of constrictions and expansions of the sleeves and therefor of the tube to produce a pumping action in one direction on the blood flow therein, said apparatus further comprising an implantable Stirling engine including a heat source for operating the engine, the engine having a working space wherein working gas experiences a cyclic pressure variation between high and low, the apparatus further comprising duct means communicating said high and low pressure gas to said valve means.

2. An implantable heart pump for pumping and controlling the flow of blood through an artery which is severable to expose two adjacent ends to accomodate the pump therebetween, this pump being operable with first and second sources of high and low pressure fluid respectively, the pump comprising a tube securable between said severed ends of said artery to form a continuous blood flow passage, at least two sleeves each at least partially surrounding said tube, the sleeves being axially spaced apart but adjacent to each other, the tube having a bore diameter that is variable between large and small, each sleeve being responsive to a pressure change whereby its diameter is variable between large and small corresponding to said tube bore diameters, valve means for communicating selectively said high and low pressure sources to said sleeves, whereby each sleeve periodically has a small diameter for constricting the tube to have a small bore diameter adjacent said sleeve, and a large diameter permitting a corresponding large bore diameter of said tube, the valve providing a predetermined sequence of constrictions and expansions of the sleeves and therefore of the tube to produce a pumping action in one direction on the blood flow therein, the pump further comprising an implantable Stirling engine including a heat source for operating the engine and a lubricating oil pump in the crankcase of the engine for providing oil under pressure, with crankcase interior being at a pressure lower than said oil pump pressure, the apparatus further comprising means communicating a portion of said oil under pressure to said valve means as said source of high pressure fluid, and means communicating the crankcase interior to said valve means as said source of low pressure fluid.

3. An implantable heart pump for pumping and controlling the flow of blood through an artery which is severable to expose two adjacent ends to accommodate the pump therebetween, this pump being operable with first and second sources of high and low pressure fluid respectively, the pump comprising an implantable Stirling engine including a heat source for operating the engine and a mechanical power output of the engine a compressor driven by said power output, the compressor having a high pressure output port and a low pressure inlet port which constitute said high and low pressure sources of fluid, duct means communicating said ports to a valve means, and corresponding high and low pressure buffer chambers respectively intermediate said valve and said ports, a tube securable between said severed ends of said artery to form a continuous blood flow passage, at least two sleeves each at least partially surrounding said tube, the sleeves being axially spaced apart but adjacent to each other, the tube having a bore diameter that is variable between large and small, each sleeve being responsive to a pressure change whereby its diameter is variable between large and small corresponding to said tube bore diameters, said valve means for communicating selectively said high and low pressure sources to said sleeves, whereby each sleeve periodically has

a. a small diameter for constricting the tube to have a small bore diameter adjacent said sleeve, and

b. a large diameter permitting a corresponding large bore diameter of said tube, the valve providing a predetermined sequence of constrictions and expansions of the sleeves and therefor of the tube to produce a pumping action in one direction on the blood flow therein.

4. An implantable heart pump for pumping and controlling the flow of blood through an artery which is severable to expose two adjacent ends to accommodate the pump therebetween, this pump being operable with first and second sources of high and low pressure fluid respectively, the pump comprising a tube securable between said severed ends of said artery to form a continuous blood flow passage, at least two sleeves each at least partially surrounding said tube, the sleeves being axially spaced apart but adjacent to each other, the tube having a bore diameter that is variable between large and small, each sleeve being responsive to a pressure change whereby its diameter is variable between large and small corresponding to said tube bore diameters, valve means for communicating selectively said high and low pressure sources to said sleeves, and wherein each sleeve comprises a tubular element defining a ringshaped hollow chamber with only one inlet-outlet port, each ring having a normal small diameter that is expandable to a large diameter when high pressure fluid is communicated to said inlet-outlet port, each ring having resilience to return to its normal small diameter when in communication with low pressure fluid whereby each sleeve periodically has a small diameter for constricting the tube to have a small bore diameter adjacent said sleeve, and a large diameter permitting a corresponding large bore diameter of said tube, the valve providing a predetermined sequence of constrictions and expansions of the sleeves and therefor of the tube to produce a pumping action in one direction on the blood flow therein.

5. An implantable heart pump for pumping and controlling the flow of blood through an artery which is severable to expose two adjacent ends to accommodate the pump therebetween, this pump being operable with first and second sources of high and low pressure fluid respectively, the pump comprising a tube securable between said severed ends of said artery to form a continuous blood flow passage, a core element formed as a rod fixedly positioned generally centrally within the bore of said tube and adjacent the inner surface thereof, at least two sleeves each at least partially surrounding said tube, the sleeves being axially spaced apart but adjacent to each other, the tube having a bore diameter that is variable between large and small, each sleeve being responsive to a pressure change whereby its diameter is variable between large and small corresponding to said tube bore diameter, valve means for communicating selectively said high and low pressure sources to said sleeves, the pump further comprising an implantable Stirling engine including a heat source for operating the engine, the engine having a working space wherein working gas experiences a cyclic pressure variation between high and low, the apparatus further comprising duct means communicating said high and low pressure gas to said valve means whereby each sleeve periodically has a small diameter for constricting the tube to have a small bore diameter adjacent said sleeve, and a large diameter permitting a corresponding large bore diameter of said tube, and constriction of each sleeve constricts the adjacent part of said tube, with the inner surface of said part urged closely against said core to prevent blood flow past said part, the valve providing a predetermined sequence of constrictions and expansions of the sleeves and therefor of the tube to produce a pumping action in one direction on the blood flow therein.

6. Apparatus according to claim 5 wherein said sleeves define an axial length between them and said core has length approximately equal to said axial length, the apparatus further comprising web means for fixedly positioning each end of said core relative to said tube.

7. A heart pump for attachment between the severed ends of a severed artery, comprising an implantable Stirling engine including a fluid therein that is cyclically under high and low pressure, a tube securable between said severed ends to form a continuous blood flow path, three sleeves axially spaced and having generally cylindrical bores positioned about and in contact with said tube, a core element formed as a rod fixedly positioned generally centrally within the bore of said tube and adjacent the inner surface thereof, valve means for cyclically and sequentially communicating said high and low pressure fluid to said sleeves, a buffer tank between said valve and each of said high and low pressure sources, means interconnecting said engine and said valve for cyclically controlling said valve according to the operation cycle of the engine, said sleeves designated first, second and third moving downstream of the flow, each having its diameter reduced when said high pressure is communicated thereto and expanded when said low pressure is communicated thereto and the tube in the areas surrounded by the sleeves having corresponding diameter constrictions and expansions with the tubes inner surface at each of said areas being urged closely against said core to prevent blood flow in said areas respectively, whereby the tube diameter adjacent the sleeves is as follows:

8. An implantable heart pump for pumping and controlling the flow of blood through an artery which is severable to expose two adjacent ends to accommodate the pump therebetween, this pump being operable with first and second sources of high and low pressure fluid respectively, the pump comprising a tube securable between said severed ends of said artery to form a continuous blood flow passage, at least two sleeves each having a generally cylindrical bore at least partially surrounding and contacting said tube, the sleeves being axially spaced apart but adjacent to each other, a core element formed as a rod fixedly positioned generally centrally within the bore of said tube and adjacent the inner surface thereof, the tube having a bore diameter that is variable between large and small, each sleeve being responsive to a pressure change whereby its diameter is variable between large and small corresponding to said tube bore diameters, and valve means for communicating selectively said high and low pressure sources to said sleeves, whereby each sleeve periodically has

a. a small diameter for constricting the tube to have a small bore diameter at the area of the tube adjacent said sleeve with the tubes's inner surface at the area being urged closely against said core to prevent blood flow in that area, and

b. a large diameter permitting a corresponding large bore diameter of said tube, and thereby permitting blood flow, the valve providing a predetermined sequence of constrictions and expansions of the sleeves and therefor of the tube to produce a pumping action in one direction on the blood flow therein.