WO2000003754A1

WO2000003754A1 - Double-tube heart-assistance system

Info

Publication number: WO2000003754A1
Application number: PCT/IL1998/000338
Authority: WO
Inventors: Dan Rottenberg
Original assignee: H.D.S. Systems, Ltd.
Priority date: 1998-07-19
Filing date: 1998-07-19
Publication date: 2000-01-27
Also published as: EP1098671A1; AU8355098A

Abstract

A heart-assistance pump system is described wherein the blood path is circulating. The system comprises (a) a variable-volume reservoir having an inlet port and an outlet port; and (b) a single cannula. The single cannula has (i) at least one internal lumen formed therein, (ii) a proximal end that is in communication with both the inlet and outlet ports and (iii) a distal end. Blood is drawn from the at least one lumen into the reservoir substantially only via the inlet port and wherein blood is expelled from the reservoir into the at least one lumen substantially only via the outlet port.

Description

DOUBLE-TUBE HEART-ASSISTANCE SYSTEM

FIELD OF INVENTION

The present invention relates generally to devices and systems for augmenting cardiac output, such as intra-ventricular, intra aortic and intra-atrium heart-assistance pumps, and in particular to heart-assistance pumps wherein the blood path is circulating.

BACKGROUND OF INVENTION Intra-ventricular, intra-aortic and intra-atrium heart-assistance devices are well known in the art. These devices are generally used to reduce the heart's work load during or after insult or surgery. They may also be used to increase blood flow from the left or right ventricle of the heart into the aorta or pulmonary artery in cases of insufficient cardiac output due, for example, to acute or chronic heart ailments or to interference with normal cardiac function during surgery.

PCT publication WO 97/02850, which is incorporated^' herein by reference, describes a heart-assistance pump comprising a cannula which has a distal end, a proximal end and an outer sheath that defines and encloses a lumen therein. The cannula is inserted through the aorta of a subject so that the distal end is inside a ventricle of the heart of said subject. The pump includes at least one inlet valve, adjacent to the distal end of the cannula, through which blood enters the lumen from the ventricle and at least one outlet valve, disposed radially along the sheath of the cannula, though which blood exits the lumen into the aorta. A fluid reservoir, having a variable volume, is connected to the proximal end of the cannula, so that blood may flow between the lumen and the reservoir. A pump drive, coupled to the fluid reservoir, controls the fluid volume in the reservoir. The pump drive alternately increases and decreases the fluid volume in the reservoir to produce a pulsatile pumping action of blood through the cannula. Similarly, PCT application PCT LL97/00386, which is incorporated herein by reference, describes a method of augmenting blood flow from a ventricle of a heart to an artery exiting the ventricle. The method comprises inserting a cannula having a distal end and a proximal end into the heart and the artery such that the distal end of the cannula is in the artery and a more proximal portion of the cannula is in the ventricle and transferring blood from the ventricle to the artery via a lumen of the cannula. Alternatively, the heart-assistance pump comprises a cannula having a distal end, an outlet valve communicating with an opening at or adjacent to the distal end of the cannula and an inlet valve communicating with an opening more proximate than the opening with which the outlet valve communicates. Similarly, PCT application PCT/IL98/00142, which is incorporated herein by reference, describes a heart-assistance pump system comprising a cannula having a distal end, an inlet valve associated with the cannula, an outlet valve associated with the cannula and an extensible protrusion, such as an inflatable balloon, adjacent to the distal end of the cannula. Additionally, a heart-assistance pump system comprising a cannula having a distal end and including an inlet valve, an outlet valve and a guide is described. The guide has a distal end and serves for positioning the cannula. The guide comprises an extensible protrusion, such as an inflatable balloon, adjacent to its distal end. Alternatively or additionally, the pump is suitable for pumping blood directly from an atrium such as the right atrium or a vein associated with the atrium, such as the vena cava, to an artery associated with the same side of the heart as the atrium, such as the pulmonary artery.

Similarly, U.S. patent 3,955,617, which is incorporated herein by reference, describes a single-lumen cannula wherein blood is directly sucked from^' the left ventricle, while blocking flow to the aorta and wherein upon the reverse cycle, the blood removed is forced into the aorta, while blocking flow back into the left ventricle.

All the heart-assistance pump systems described above are single-lumen pumps, where the blood travels in one direction, then in the other direction within the same lumen. In single- lumen pumps, all the blood in the pump is not expelled during a pumping cycle. In other words, some blood is stagnant within the pump. This may lead to clot formation. Another possible problem with such pumps is a long exposure of some of the blood components to artificial materials, wherein the possibility of stagnation can aggravate the problem and may lead to clot formation.

Still another possible problem is that cyclic changes in flow direction increase mixing, hence turbulence, in the blood. Turbulent flow in itself can cause damage to blood cells, as they hit against one another and suffer mechanical stresses.

SUMMARY OF THE INVENTION It is an object of some aspects of the present invention to provide a heart-assistance pump system wherein stagnation in the blood flow is avoided, the period of contact between the blood components and any mechanical parts is minimized, and turbulence is reduced to a minimum.

One aspect of some preferred embodiments of the invention provides a heart-assistance pump system with a blood path that is completely or partially circulating. Instead of blood traveling in one direction, then in the other direction, within a single lumen, it travels in direction of the pump in one lumen and away from same pump in another. A double-lumen heart-assistance pump system will prevent stagnation in blood flow, reduce turbulence in blood flow and minimize mechanical stresses to blood components.

In some preferred embodiments of the present invention, a heart-assistance pump comprises a hydraulic pump, a cannula of at least one lumen and a pulsatile drive unit.

In accordance with these preferred embodiments, the pump is preferably made up of a reservoir of variable volume, an inlet tube having an inlet lumen formed therein and an outlet tube having an outlet lumen formed therein, with each tube having a distal end and a proximal end. Preferably, the tubes are connected to the reservoir at their proximal ends via two fluid ports, an inlet port and an outlet port. Preferably, an inlet valve, situated within the inlet tube or in the inlet port and preferably, an outlet valve, situated within the outlet tube or in the outlet port, allow substantially only one-way flow in the tubes, from the cannula to the reservoir in the inlet tube and from the reservoir to the cannula in the outlet tube.

Preferably, the cannula comprises a distal end, a proximal end and a single lumen formed therein. Preferably, the proximal end of the cannula is connected to the distal ends of the inlet and outlet tubes, preferably, via a 3-port fitting.

Preferably, the cannula includes an inlet-outlet valve unit at its distal end and preferably, the distal end of the cannula is inserted into a heart in accordance with a particular configuration, so as to draw blood from a ventricle or an atrium or a vein of a heart, as required and to expel blood to an artery of the same side of the heart, while the 3-port fitting at the proximal end of the cannula remains outside the body, except in the case of an open-heart surgery where the cannula is inserted directly into the left or right ventricle or atrium. The 3- port fitting is then outside the heart.

In accordance with these preferred embodiments, variations in the volume of the reservoir cause the pumping action. As the reservoir volume is increased, the inlet valves (at the distal end of the cannula and within the inlet tube or the inlet port) open, while all outlet valves are shut: blood flows from a ventricle or an atrium or a vein of a heart, as required, into the cannula. Thence, via the 3-port fitting to the inlet tube and from it to the reservoir. The reservoir volume is then decreased, causing all inlet valves to shut, causing the outlet valves (at the distal end of the cannula and within the outlet tube or the outlet port) to open and pushing the blood through the outlet tube, via the 3-port fitting to the cannula and through the cannula's outlet valve (or valves) to the artery of the same side of the heart. In accordance with these preferred embodiments, pump drive 96 is preferably driven by a servo mechanism 94, under the control of an internal computer 92. Internal computer 92 regulates the rate and stroke volume of a piston in pump drive 96. Preferably, internal computer 92 receives physiological signal inputs, such as EKG and blood pressure signals, and uses these signals to optimally control pump drive 96. Preferably, pump drive 96 operates at the rate of the heart beat.

In some preferred embodiments of the present invention, the system is a ventricle-to-artery system, configured to pump blood from a ventricle to an artery of the same side of a heart. Alternatively, the system is an atrium-to-artery system, configured to pump blood from an atrium to an artery of the same side of a heart. Alternatively, the system is a by-pass system, configured to pump blood from a vein to an artery of the right side of a heart.

However, the invention is not limited to pumps using the 3-port fitting as a connector between the cannula and the inlet and outlet tubes. In other preferred embodiments of the present invention, an appropriate connector as known in the art may be advantageously used in place of the 3-port fitting. Alternatively, the cannula and the inlet and outlet tubes can be manufactured as a single unit.

In some preferred embodiments of the present invention, an alternative cannula design is used. The cannula has a single lumen at its distal end and a double lumen at its proximal end, wherein the double lumen constitutes an inlet lumen and an outlet lumen and wherein the proximal end of the double-lumen portion of the cannula is connected to the reservoir via the two fluid ports. Preferably, the inlet lumen is in communication with the inlet port and the outlet lumen is in communication with the outlet port. Preferably, an inlet valve, situated within the inlet lumen or in the inlet port and preferably, an outlet valve, situated within the outlet lumen or in the outlet port, allow only one-way flow in the double-lumen portion of the cannula, into the reservoir via the inlet lumen and out of the reservoir via the outlet lumen.

Preferably, the single-lumen portion of the cannula and the double-lumen portion of the cannula share a common sheathing. However, the invention is not limited to pumps using a common sheathing to connect the two portions. In other preferred embodiments of the present invention, an appropriate connector as known in the art may be advantageously used or the lumens may be attached to each other without a sheath.

Preferably, the cannula includes an inlet-outlet valve unit at the distal end of the single- lumen portion and preferably, the single-lumen portion of the cannula is inserted into a heart in accordance with a particular configuration, so as to draw blood from a ventricle or an atrium or a vein of a heart, as required and to expel blood to an artery of the same side of the heart. The point of connection between the single-lumen portion of the cannula and the double-lumen portion of the cannula remains outside the body, except in the case of an open-heart surgery in which the single-lumen portion of the cannula is inserted directly into the left ventricle. The point of connection is then outside the heart.

In some preferred embodiments of the present invention, a still alternative design may be used. The cannula comprises a double lumen throughout its length and preferably, the two lumens are separated by a flexible dividing wall which acts as a thin diaphragm to provide greater volume to either lumen when blood flows through it. Preferably, the double lumen constitutes an inlet lumen and an outlet lumen and preferably, the proximal end of the cannula is connected to the reservoir via the two fluid ports: the inlet lumen is in communication with the inlet port and the outlet lumen is in communication with the outlet port.

Preferably, an inlet valve, situated preferably in the inlet port and preferably, an outlet valve, situated preferably in the outlet port, allow only one-way flow in the double-lumen cannula, into the reservoir via the inlet lumen and out of the reservoir via the outlet lumen. Blood flow in this cannula is completely circular.

Preferably, the double-lumen cannula includes two distal one-way valves at its distal end, one being a distal inlet valve and the other being a distal outlet valve. Preferably, the valves are radially disposed; therefore, unaffected by the changes in the size of the lumen. Preferably, the distal end of the carmula is inserted into a heart in accordance with a particular configuration, so as to draw blood from a ventricle or an atrium or a vein of a heart, as required and to expel blood to an artery of the same side of the heart. The distal inlet and outlet valves are within the heart. Blood flow in this cannula is completely circular.

In some preferred embodiments of the present invention, a further alternative design may be used. The cannula comprises a double lumen throughout its length and preferably, the two lumens are separated by a wall of the same material as the cannula. Preferably, the double lumen constitutes an inlet lumen and an outlet lumen. Preferably, the proximal end of the cannula is connected to the reservoir via the two fluid ports, the inlet lumen being in communication with the inlet port and the outlet lumen being in communication with the outlet port.

Preferably, an inlet valve, situated preferably within the inlet lumen or in the inlet port and preferably, an outlet valve, situated preferably within the outlet lumen or in the outlet port, allow only one-way flow in the double-lumen cannula, into the reservoir in the inlet lumen and out of the reservoir in the outlet lumen.

Preferably, this cannula has only one set of inlet and outlet valves, associated with the inlet and outlet ports of the reservoir and blood flow in this system is completely circular. Preferably, the two lumens are not of equal length, as described by the examples below:

In preferred embodiments of the present invention where the system is a ventricle-to-artery system and the point of incision is at the apex of the left ventricle, the double-lumen cannula is inserted into the left ventricle, but only the outlet lumen extends downstream past the aortic valve to the aorta. In preferred embodiments of the present invention where the system is a ventricle-to-artery system and the point of insertion is at an artery, the double-lumen cannula is inserted via an artery to the aorta, but only the inlet lumen extends upstream past the aortic valve to the left ventricle.

In preferred embodiments of the present invention where the system is a by-pass system and the point of incision is a vein, such as the vena cava, the double-lumen cannula is inserted into the vena cava, but only the outlet lumen extends past the right atrium and the right ventricle to the pulmonary artery.

In preferred embodiments of the present invention, where the cannula is inserted in the direction of the blood flow, such as from the vena cava to the right atrium to the pulmonary artery, an attached extensible protrusion, such as an inflatable balloon, may be provided as a guide for positioning the cannula' s distal end. This guiding system is described in patent application PCT/IL98/00142.

In preferred embodiments of the present invention, the single-lumen cannula, the inlet tube, the outlet tube and the double-lumen cannula are made of a flexible, resilient material. The overall diameter (or width) of the cannula is preferably in the range of 12-45 French (4-15 mm), but it may be larger. The 3-port fitting is preferably made of polycabonate or some other suitable material.

In preferred embodiments of the present invention, the cannula' s inlet and outlet valves are those described in one or more of the following patents and patent applications: PCT IL96/00044, PCT/IL97/00201, WO 97/02850, PCT/IL97/00386 and PCT/TL98/00142.

However, the invention is not limited to pumps using these valves and other valves, as known in the art, may be advantageously utilized. In preferred embodiments of the present invention, the inlet-tube valve and the outlet-tube valve are those described in patent application PCT/IL96/00044. However, the invention is not limited to pumps using these valves and other valves, as known in the art, may be advantageously utilized. In preferred embodiments of the present invention, the pulsatile drive unit and the variable- volume reservoir are those described in the following patent applications: WO 97/02850, PCT/IL97/00386 and PCT/IL98/00142. However, the invention is not limited to pumps using these units and other pulsatile drive units and other types of variable-volume reservoirs as known in the art, may be advantageously utilized. A heart-assistance pump according to some aspects of the invention differs from prior-art pumps in the use of a blood path that is completely or partially circulating, thereby eliminating the possibility of blood stagnation at low blood flow rates and reducing the extent of turbulence at higher blood flow rates, thus reducing the risk of clot formation and reducing the risk of damage to blood components. There is thus provided, in accordance with a preferred embodiment of the invention, a heart- assistance pump system comprising:

(a) a variable-volume reservoir having an inlet port and an outlet port; and

(b) a single cannula having: i. at least one internal lumen formed therein, ii. a proximal end that is in communication with both the ihlet and outlet ports and iii. a distal end, wherein blood is drawn .from the at least one lumen into the reservoir substantially only via the inlet port and wherein blood is expelled from the reservoir into the at least one lumen substantially only via the outlet port. Preferably, the pump includes a blood inlet adjacent to the distal end of the cannula, through which blood is drawn into the at least one lumen; and a blood outlet proximate to the blood inlet, through which blood is expelled from the at least one lumen. Preferably, the pump includes a blood outlet adjacent to the distal end of the cannula, through which blood is expelled from the at least one lumen; a blood inlet proximate to the blood outlet, through which blood is drawn into the at least one lumen.

Preferably, the at least one lumen communicates with the inlet port of the reservoir via an inlet lumen and wherein the at least one lumen communicates with the outlet port of the reservoir via an outlet lumen.

In a preferred embodiment of the invention, the pump system comprises a one-way" valve associated with the inlet port which limits blood flow substantially to one direction, from the inlet lumen into the reservoir. In a preferred embodiment of the invention, the one-way valve associated with the inlet port is situated within the inlet lumen. Alternatively, the one- way valve associated with the inlet port is situated at the inlet port.

In a preferred embodiment of the invention the pump system comprises a one-way valve associated with the outlet port which limits blood flow substantially to one direction, from the reservoir into the outlet lumen. In a preferred embodiment of the invention, the oneway valve associated with the outlet port is situated within the outlet lumen. Alternatively, the one-way valve associated with the outlet port is situated at the outlet port. Preferably, the pump system comprises an inlet tube having a proximal end and a distal end and having said inlet lumen formed therein; and an outlet tube having a proximal end and a distal end and having said outlet lumen formed therein; wherein the proximal end of the inlet tube is connected to the inlet port of the reservoir and wherein the proximal end of the outlet tube is connected to the outlet port of the reservoir.

Preferably, the at least one lumen is a single axial lumen and wherein the proximal end of the single axial lumen is connected to the distal ends of the inlet and outlet tubes. In a preferred embodiment of the invention, the at least one lumen is a single axial lumen at the distal end of the cannula and a double axial lumen at the proximal end of the cannula and wherein said double lumen forms at least a portion of the inlet and outlet lumens. Preferably, the single-lumen portion of the cannula and the double-lumen portion of the cannula share a common sheathing. In a preferred embodiment of the invention, the at least one lumen comprises a double lumen throughout a portion of its length and wherein one lumen of the double lumen ends in one of the blood inlet or the blood outlet at a distal end of said one lumen and wherein the other lumen of the double lumen ends in the other blood inlet or the blood outlet at a distal end of said other lumen, wherein the distal end of said other lumen is more distal than the distal end of said one lumen.

Preferably, the two lumens of the double lumen are separated by a flexible dividing wall which acts as a thin diaphragm to provide greater volume to either lumen when blood flows through it.

Preferably, the two lumens of the double-lumen portion of the cannula communicate at their proximal ends to the inlet and outlet ports of the reservoir respectively.

In a preferred embodiment of the invention, the system comprises a one-way valve situated at the blood inlet which limits blood flow substantially to one direction, into the at least one lumen of the cannula.

In a preferred embodiment of the invention, the system comprises a one-way valve situated at the blood outlet which limits blood flow substantially to one direction, out of the at least one lumen of the cannula.

In some preferred embodiments of the invention the blood inlet has no one-way valve associated with it. In some preferred embodiments of the invention, the blood outlet has no one-way valve associated with it.

There is further provided, in accordance with a preferred embodiment of the invention method for use of the heart-assistance pump system in accordance with some of the preferred embodiments thereof for augmenting the blood output of the heart, where that method comprises:

(a) inserting the cannula into the cardiovascular system via an artery to the aorta and to the left ventricle;

(b) drawing blood from the left ventricle, through the blood inlet of the cannula and into the reservoir, by increasing the volume of the reservoir; and (c) expelling blood from the reservoir through the blood outlet of the cannula and into the aorta, by reducing the volume of the reservoir.

(a) inserting the cannula to the cardiovascular system inserted via an artery to the left atrium and through the left ventricle to the aorta; (b) drawing blood from the left ventricle, through the blood inlet of the cannula and into the reservoir, by increasing the volume of the reservoir; and

(c) expelling blood from the reservoir through the blood outlet of the cannula and into the aorta, by reducing the volume of the reservoir. There is further provided, in accordance with a preferred embodiment of the invention method for use of the heart-assistance pump system in accordance with some of the preferred embodiments thereof for augmenting the blood output of the heart, where that method comprises:

(a) inserting the cannula to the cardiovascular system via an incision in the left ventricle and to the aorta;

(b) drawing blood from the left ventricle, through the blood inlet of the cannula and into the reservoir, by increasing the volume of the reservoir; and

(a) inserting the cannula to the cardiovascular system via the vena cava to the right atrium and through the right ventricle to the pulmonary artery;

(b) drawing blood from the vena cava, through the blood inlet of the cannula and into the reservoir, by increasing the volume of the reservoir; and

(c) expelling blood from the reservoir through the blood outlet of the cannula and into the pulmonary artery, by reducing the volume of the reservoir. There is further provided, in accordance with a preferred embodiment of the invention method for use of the heart-assistance pump system in accordance with some of the preferred embodiments thereof for augmenting the blood output of the heart, where that method comprises:

(b) drawing blood from the right atrium, through the blood inlet of the cannula and into the reservoir, by increasing the volume of the reservoir; and (c) expelling blood from the reservoir through the blood outlet of the cannula and into the pulmonary artery by reducing the volume of the reservoir.

(a) inserting the cannula to the cardiovascular system inserted via the vena cava to the right atrium and through the right ventricle to the pulmonary artery;

(b) drawing blood from the right ventricle, through the blood inlet of the cannula and into the reservoir, by increasing the volume of the reservoir; and

(c) expelling blood from the reservoir through the blood outlet of the cannula and into the pulmonary artery, by reducing the volume of the reservoir.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more clearly understood with reference to the following detailed descriptions of non- limiting preferred embodiments of the invention in which:

Fig. 1 is a schematic, partially sectional representation of a heart-assistance pump, in accordance with a preferred embodiment of the present invention, illustrating a cannula with a 3-port fitting from which two tubes extend to the blood reservoir;

Fig. 2 is a schematic representation of a heart-assistance pump, in accordance with a preferred embodiment of the present invention, illustrating the percutaneous insertion of a cannula thereof into the heart through the apex of the left ventricle;

Fig. 3 is a schematic representation of a heart-assistance pump, in accordance with a preferred embodiment of the present invention, illustrating the percutaneous insertion of a cannula thereof through a peripheral artery (such as the femoral artery), via the aorta and into the left ventricle;

Fig. 4 is a schematic representation of a heart-assistance pump, in accordance with a preferred embodiment of the present invention, illustrating the percutaneous insertion of a cannula thereof through the vena cava, via the right atrium, to the pulmonary artery. The figure also illustrates a balloon system that can be used for positioning the cannula; Fig. 5 is a schematic, partially sectional representation of a heart-assistance pump, in accordance with a preferred embodiment of the present invention, illustrating a cannula having a double-lumen portion at its proximal end and a single-lumen portion at its distal end; Fig. 6 is a partially schematic, sectional representation of a heart-assistance pump, in accordance with still another preferred embodiment of the present invention, having a double- lumen cannula and no inlet-outlet valve unit at the distal end of the cannula; and

Fig. 7 is a schematic representation of a heart-assistance pump, in accordance with a preferred embodiment of the present invention, illustrating the percutaneous insertion of a double-lumen cannula thereof into the heart through the apex of the left ventricle. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Reference is now made to Fig. 1 , which schematically illustrates a sectional representation of a heart-assistance pump system 10, in accordance with a preferred embodiment of the invention. Preferably, heart-assistance pump system 10 comprises a pump 20, a cannula 40 and a pulsatile drive unit 90.

Preferably, pump 20 comprises a reservoir of variable volume 60, an inlet tube 22 and an outlet tube 32. Preferably, inlet tube 22, having a proximal end 23 and a distal end 25, is connected to reservoir 60, at its proximal end 23, via an inlet port 24 and to cannula 40, at its distal end 25, via one port of a 3-port fitting 50. Preferably, inlet tube 22 contains a one-way, axially disposed inlet valve 26, preferably a three-leaflet valve described in patent application

PCT/LL96/00044, which allows only one-way flow, from cannula 40 to reservoir 60. However, in other preferred embodiments of the invention, other valves, as known in the art, may be advantageously utilized. Preferably, outlet tube 32, having a proximal end 33 and a distal end 35, is connected to reservoir 60, at its proximal end 33, via an outlet port 34 and to cannula 40, at its distal end 35, via a second port of 3-port fitting 50. Preferably, outlet tube 32 contains a one-way, axially disposed outlet valve 36, preferably a three-leaflet valve described in patent application

PCT/LL96/00044, which allows only one-way flow, from reservoir 60 to cannula 40. However, in other preferred embodiments of the invention, other valves, as known in the art, may be advantageously utilized.

Preferably, cannula 40, having a proximal end 41 and a distal end 43, is connected to the third port of 3-port fitting 50 at its proximal end 41. Preferably, cannula 40 includes an inlet- outlet valve unit 42 at its distal end 43. Preferably, valve unit 42 contains several radially disposed inlet valves 44 and an axially disposed outlet valve 46. Preferably, inlet valves 44 and outlet valve 46 are one or more of those described in the following patent applications: PCT/IL96/00044, PCT/IL/97/00201, WO 97/02850, PCT/IL98/00142 and PCT/IL97/00386. However, in other preferred embodiments of the invention, other valves, as known in the art, may be advantageously utilized. In some preferred embodiments of the invention valve 44 is constructed to be an outlet valve and valve 46 is constructed to be an inlet valve.

Reference is now additionally made to Fig. 2 to illustrate the operation of the pump system in one use thereof. Fig. 2 schematically illustrates a ventricle-to-artery system, involving a heart 70, a left ventricle 72, an aortic valve 74 and an aorta 76, in accordance with a preferred embodiment of the present invention. Preferably, distal end 43 of cannula 40 is inserted into heart 70 through an incision in the apex of left ventricle 72 and is passed downstream through aortic valve 74 into aorta 76. Preferably, the length of cannula 40 is such that when distal end 43 is positioned in aorta 76, 3-port fitting 50 remains outside heart 70, close to the point of incision in the apex. Preferably, valve unit 42 of cannula 40 is positioned so as to draw blood from ventricle 72 and expel blood to aorta 76.

In accordance with this preferred embodiment of the present invention, variations in the volume of reservoir 60 provide the pumping action in the following manner. Preferably, as the volume of reservoir 60 is increased, inlet valves 44 of cannula 40 and inlet valve 26 of inlet tube 22 open, while all outlet valves are shut. Blood flows from ventricle 72 into cannula 40, via 3-port fitting 50 to the inlet tube 22 and from it to reservoir 60. Preferably, the volume of reservoir 60 is then decreased, causing all inlet valves to shut, causing outlet valve 46 of cannula 40 and outlet valve 36 of outlet tube 32 to open and pushing the blood through outlet tube 32, via the 3-port fitting 50, to cannula 40 and through outlet valve 46 to aorta 76. Referring back to Fig. 1, preferably, reservoir 60 is made up of two chambers, a blood reservoir 62 and a secondary-fluid reservoir 64. Preferably, the secondary fluid reservoir is filled with a saline solution or another suitable liquid. Preferably, a flexible diaphragm 65 separates the two chambers so that they are of equal pressure, yet, there is no mingling of fluids. Preferably, blood reservoir 62 communicates with cannula 40 via inlet port 24 and inlet tube 22 and via outlet port 34 and outlet tube 32. Preferably, secondary-fluid reservoir 64 communicates with pulsatile drive unit 90 via a secondary-fluid port 66 and a secondary fluid tube 68.

Preferably, pulsatile drive unit 90 includes an internal computer 92 in communication with a servo mechamsm 94. Preferably, the servo mechanism is in communication with piston- cylinder stroke mechanism 96. Preferably, the pulsatile drive unit is of the type described in patent applications, WO 97/02850, PCT/IL98/00142 and PCT/IL97/00386. However, in other preferred embodiments of the invention, other pumping systems, as known in the art, may be advantageously utilized. Preferably, pulsatile drive unit 90, responsive to EKG, pressure or other signals, effects the changes in the pumping rate and volume of reservoir 60, hence, the pumping action.

Reference is now made to Fig. 3 to illustrate the operation of the pump system in another ventricle-to-artery use thereof, in accordance with another preferred embodiment of the present invention. Preferably, distal end 43 of cannula 40 is inserted into heart 70 through an incision, in a peripheral artery (such as the femoral artery) and upstream, via aorta 76, into left ventricle 72. Preferably, the length of cannula 40 is such that when distal end 43 is positioned in left ventricle 72, 3-port fitting 50 remains outside the body, close to the point of incision. Preferably, valve unit 42 of cannula 40 is positioned so as to draw blood from ventricle 72 and expel blood to aorta 76.

Reference is now made to Fig. 4 to illustrate the operation of the pump system in an atrium-to-artery use thereof, involving a vena cava 77, right atrium 78, a right ventricle 79, a pulmonary valve 80 and a pulmonary artery 81, in accordance with another preferred embodiment of the present invention. Preferably, distal end 43 of cannula 40 is inserted into heart 70 through vena cava 77 and downstream to right atrium 78, to right ventricle 79 and, via pulmonary valve 80, to pulmonary artery 81. Preferably, the length of cannula 40 is such that when distal end 43 is positioned in pulmonary artery 81, 3-port fitting 50 remains outside the body, close to the point of incision. Preferably, valve unit 42 of cannula 40 is positioned so as to draw blood from right atrium 78 and expel blood to pulmonary artery 81. Fig.4 also illustrates a balloon 82 at distal end 43, as a positioning guide, in accordance with patent application PCT/LL98/00142.

In preferred embodiments of the present invention, cannula 40, inlet tube 22 and outlet tube 32 are made of a flexible, resilient material. The overall diameter of cannula 40 is preferably in the range of 12-45 French (4-15 mm), but it may be larger. Three-port fitting 50 is preferably made of polycabonate or some other suitable material.

Reference is now made to Fig. 5, which schematically illustrates a sectional representation of a heart-assistance pump system 100, in accordance with a preferred embodiment of the invention. Preferably, heart-assistance pump system 100 comprises a pump 102, a pulsatile drive unit 90 and a cannula 98 having a double-lumen portion 105 and a single-lumen portion 107.

Preferably, cannula 98 comprises a proximal end 101 and a distal end 103. Preferably, double-lumen portion 105 constitutes an inlet lumen 106 and an outlet lumen 108. Preferably, double-lumen portion 105 is in connected to fluid ports 24 and 34, so that inlet lumen 106 is in communication with inlet port 24 and outlet lumen 108 is in communication with outlet port 34. Preferably, an inlet valve 26, situated in inlet port 24 and preferably, an outlet valve 36, situated in the outlet port 34, allow substantially only one-way flow in the double-lumen portion of the cannula, into reservoir 60 from inlet lumen 106 and out of reservoir 60 into outlet lumen 108.

Preferably, single-lumen portion 107 and double-lumen portion 105 share a common sheathing 104 and are connected at point 99. However, the invention is not limited to pumps using a common sheathing to connect the two portions. In other preferred embodiments of the present invention, an appropriate connector as known in the art may be advantageously used or the lumens may be attached to each other without a sheath.

Preferably, cannula 98 includes an inlet-outlet valve unit adjacent to distal end 103 and preferably, only single-lumen portion 107 is inserted into a heart in accordance with a particular configuration. Thus, blood is drawn from a ventricle or an atrium or a vein of a heart, as required and is expelled to an artery of the same side of the heart. Generally, point of connection 99 remains outside the body, except in the case of an open-heart surgery in which single-lumen portion 107 is inserted directly into the left ventricle. Point of connection 99 is then outside the heart.

Reference is now made to Fig. 6, which schematically illustrates a sectional representation of a heart-assistance pump system 110, in accordance with another preferred embodiment of the invention, including a double-lumen cannula 120, which is preferably produced as a single extrusion of two tubes having a common wall. The double-lumen cannula provides an inlet lumen 122 and an outlet lumen 132. Preferably, this cannula does not utilize inlet-outlet valve unit 42 and the blood flow in this cannula is completely circular. Preferably, the two lumens have a common proximal end 123. Preferably, inlet lumen 122 connects to reservoir 60 at proximal end 123 via inlet port 24 and includes inlet valve 26. Outlet lumen 132 preferably connects to reservoir 60 at proximal end 123 via outlet port 34 and includes outlet valve 36.

Preferably, inlet valve 26 and outlet valve 36 are near proximal end 123. Preferably, the two lumens are not of equal length, inlet lumen 122 having a distal end 125 and outlet lumen 132 having a distal end 135, as illustrated by the preferred embodiment in Figs. 6 and 7. Reference is now made to Fig. 7 to illustrate the operation of pump system 110 in one use thereof. Fig. 7 schematically illustrates a ventricle-to-artery system, using double-lumen system

110, in accordance with a preferred embodiment of the present invention. Preferably, cannula

120 is inserted into heart 70 through an incision in the apex of left ventricle 72, so that distal end 125 of inlet lumen 122 is positioned in left ventricle 72, while distal end 135 of outlet lumen 132 extends downstream through aortic valve 74 into aorta 76. In this way, the cannula draws blood from ventricle 72 and expels it to aorta 76.

This type of pump may also advantageously be used for ventricle-to-artery systems inserted via the arteries and for right side of heart, heart-assistance systems.

In preferred embodiments of the present invention, double-lumen cannula 120 is made of a flexible, resilient material. The overall diameter of double-lumen cannula 120 is preferably in the range of 12-45 French (4-15 mm), but it may be larger.

The present invention has been described using non-limiting detailed descriptions of preferred embodiments thereof that are provided by way of examples and are not intended to limit the scope of the invention. Variations of embodiments described will occur to persons of the art. The scope of the invention is limited only by the following claims:

Claims

1. A heart-assistance pump system comprising:

(a) a variable- volume reservoir having an inlet port and an outlet port; and (b) a single cannula having: i. at least one internal lumen formed therein, ii. a proximal end that is in communication with both the inlet and outlet ports and iii. a distal end, wherein blood is drawn from the at least one lumen into the reservoir substantially only via the inlet port and wherein blood is expelled from the reservoir into the at least one lumen substantially only via the outlet port.

2. A heart-assistance pump system according to claim 1 comprising:

(a) a blood inlet adjacent to the distal end of the cannula, through which blood is drawn into the at least one lumen;

(b) a blood outlet proximate to the blood inlet, through which blood is expelled from the at least one lumen.

3. A heart-assistance pump system according to claim 1 , comprising: (a) a blood outlet adjacent to the distal end of the cannula, through which blood is expelled from the at least one lumen; (b) a blood inlet proximate to the blood outlet, through which blood is drawn into the at least one lumen.

4. A heart-assistance pump system according to claim 2 or claim 3 wherein the at least one lumen communicates with the inlet port of the reservoir via an inlet lumen and wherein the at least one lumen communicates with the outlet port of the reservoir via an outlet lumen.

5. A heart-assistance pump system according to claim 4, comprising a one-way valve associated with the inlet port which limits blood flow substantially to one direction, from the inlet lumen into the reservoir.

6. A heart-assistance pump system according to claim 5 wherein the one-way valve associated with the inlet port is situated within the inlet lumen.

7. A heart-assistance pump system according to claim 5 wherein the one-way valve associated with the inlet port is situated at the inlet port.

8. A heart-assistance pump system according to any of claims 4 - 7 comprising a one-way valve associated with the outlet port which limits blood flow substantially to one direction, from the reservoir into the outlet lumen.

9. A heart-assistance pump system according to claim 8 wherein the one-way valve associated with the outlet port is situated within the outlet lumen.

10. A heart-assistance pump system according to claim 8 wherein the one-way valve associated with the outlet port is situated at the outlet port.

11. A heart-assistance pump system according to any of claims 4 - 10 comprising:

(a) an inlet tube having a proximal end and a distal end and having said inlet lumen formed therein; (b) an outlet tube having a proximal end and a distal end and having said outlet lumen formed therein; wherein the proximal end of the inlet tube is connected to the inlet port of the reservoir and wherein the proximal end of the outlet tube is connected to the outlet port of the reservoir.

12. A heart-assistance pump system according to claim 11 wherein the at least one lumen is a single axial lumen and wherein the proximal end of the single axial lumen is connected to the distal ends of the inlet and outlet tubes.

13. A heart-assistance pump system according to any of claims 4 - 10 wherein the at least one lumen is a single axial lumen at the distal end of the cannula and a double axial lumen at the proximal end of the cannula and wherein said double lumen forms at least a portion of the inlet and outlet lumens.

14. A heart-assistance pump system according to claims 13 wherein the single- lumen portion of the cannula and the double-lumen portion of the cannula share a common sheathing.

15. A heart-assistance pump system according to any of claims 4 - 10 wherein the at least one lumen comprises a double lumen throughout a portion of its length and wherein one lumen of the double lumen ends in one of the blood inlet or the blood outlet at a distal end of said one lumen and wherein the other lumen of the double lumen ends in the other blood inlet or the blood outlet at a distal end of said other lumen, wherein the distal end of said other lumen is more distal than the distal end of said one lumen.

16. A heart-assistance pump system according to any of claims 13 - 15 wherein the two lumens of the double lumen are separated by a flexible dividing wall which acts as a thin diaphragm to provide greater volume to either lumen when blood flows through it.

17. A heart-assistance pump system according to any of claims 13 - 16 wherein the two lumens of the double-lumen portion of the cannula communicate at their proximal ends to the inlet and outlet ports of the reservoir respectively.

18. A heart-assistance pump system according to any of claims 2 - 17 comprising a one-way valve situated at the blood inlet which limits blood flow substantially to one direction, into the at least one lumen of the cannula.

19. A heart-assistance pump system according to any of claims 2 - 18 comprising a one-way valve situated at the blood outlet which limits blood flow substantially to one direction, out of the at least one lumen of the cannula.

20. A heart-assistance pump system according to claim 15 wherein the blood inlet has no oneway valve associated with it.

21. A heart-assistance pump system according to claim 15 or claim 20 wherein the blood outlet has no one-way valve associated with it.

2. A method for use of the heart-assistance pump system in accordance with any of claims 2- 21, for augmenting the blood output of the heart, where that method comprises: (a) inserting the cannula into the cardiovascular system via an artery to the aorta and to the left ventricle; (b) drawing blood from the left ventricle, through the blood inlet of the cannula and into the reservoir, by increasing the volume of the reservoir; and (c) expelling blood from the reservoir through the blood outlet of the cannula and into the aorta, by reducing the volume of the reservoir.

23. A method for use of the heart- assistance pump system in accordance with any of claims 2- 21, for augmenting the blood output of the heart, where that method comprises:

(a) inserting the cannula to the cardiovascular system inserted via an artery to the left atrium and through the left ventricle to the aorta;

(c) expelling blood from the reservoir through the blood outlet of the cannula and into the aorta, by reducing the volume of the reservoir.

24. A method for use of the heart-assistance pump system in accordance with any of claims 2- 21, for augmenting the blood output of the heart, where that method comprises:

25. A method for use of the heart-assistance pump system in accordance with any of claims 2- 21, for augmenting the blood output of the heart, where that method comprises: (a) inserting the cannula to the cardiovascular system via the vena cava to the right atrium and through the right ventricle to the pulmonary artery; (b) drawing blood from the vena cava, through the blood inlet of the cannula and into the reservoir, by increasing the volume of the reservoir; and (c) expelling blood from the reservoir through the blood outlet of the cannula and into the pulmonary artery, by reducing the volume of the reservoir.

26. A method for use of the heart-assistance pump system in accordance with any of claims 2- 21, for augmenting the blood output of the heart, where that method comprises:

27. A method for use of the heart-assistance pump system in accordance with any of claims 2- 21, for augmenting the blood output of the heart, where that method comprises: (a) inserting the cannula to the cardiovascular system inserted via the vena cava to the right atrium and through the right ventricle to the pulmonary artery;