CA2226491A1

CA2226491A1 - Heart assist system

Info

Publication number: CA2226491A1
Application number: CA002226491A
Authority: CA
Inventors: Dan Rottenberg; Dudu Haimovich
Original assignee: Individual
Current assignee: Medicard Ltd
Priority date: 1995-07-10
Filing date: 1996-07-08
Publication date: 1997-01-30
Also published as: WO1997002850A1; IL114517A0; JPH11514251A; AU6317596A; EP0837704A1

Abstract

A cardiac assist pump, including: a cannula, including an outer sheath, which defines and encloses a lumen therein, the cannula having a distal end and a proximal end. 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 intake valve, adjacent to the distal end of the cannula, through which blood enters the lumen from the ventricle; at least one outlet valve, disposed radially along the sheath of the cannula, through which blood exits the lumen into the aorta; a fluid reservoir having a variable fluid volume, connected to the proximal end of the cannula, such that blood may flow between the lumen and the reservoir; and a pump drive, coupled to the fluid reservoir and controlling 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.

Description

W O 97/028S0 PCT~196/00045 HEART ASSIST SYSTEM
FIELD OF T~IE INVENTION
The present invention relates generally to devices and systems for ~u~ ;lID cardiac output, and specifically to intra-ventricular cardiac assist pumps.
BACKGROUND OF TE{E INVENTION
Intra-aortic and intra-ventricular cardiac assist devices are well known in the art. These devices are ~enerally used to reduce the heart's work load a~cer insult or surgery. They may also be used to increase blood flow from the le~ ventricle of the heart into the aorta in cases of insufficient cardiac output due, for example, to acute or chronic heart ~ilmçnt5 or to interference with normal cardiac function during surgery.
One of the best-known and most widely-used intra-aortic pump systems is the Intra-Aortic Balloon Pump (IABP), comprisino a catheter, having an inflatable balloon at its distal end, which is inserted throuoh an arterv into the aorta. The balloon is then alternately inflated and deflated by an external pump drive, so as to alternately block and unblock blood flow through the aorta, in synchrony with the beating of the heart, in order to assist the left ventricle in propelling blood into the arterial system. The IABP, however, provides only limited ~t-c,m~nt~tion ofthe heart's natural, unassisted output, and is not adequate for o~el~o~ g heart failure.
U.S. patent 4,014,317, which is incorporated herein by reference, describes a

2 0 cardiocirculato}v assist cannula with a balloon pump and cardiac pacing electrode. The cannula is inserted percutaneously through the aorta so that its distal end is inside the left vemricle of the heart. L~uring systole, inlet valves on the cannula inside the left ventricle open, and the contraction of the ventricle forces blood to flow into the c~nn~ Then, during diastole, the blood flows out, into the aorta, throu(Jh one or more outlet valves along the cannula do~,l~Ll~al" from the inlet valve. A gas-filled balloon, similar in function to the IABP
described above, is connected to the cannula downstream of the outlet valves. The balloon is typically inflated durin, diastole and deflated during systole, to assist in perfusion of the coronary arteries. The cannula has a small stroke volume, however, and relies on the contractile force of the heart to pump the blood. It is therefore of limited us~.fi-lnPss in

3 0 ~lom~ntino the blood output of a weakened or failin2 heart.
U.S. patent 4,906,2''9, which is also incorporated herein by reference, describes a high-frequency transvalvular axisymmetric blood pump. The pump includes a small internal volume, s which may be alternately expanded and reduced by pneumatic or hydraulic pressure which is exerted via a flexible membrane radially surrounding the volume. The volume has intake and 3 5 outlet ends, with one-way axial valves at both of the ends, so that blood can flow only from the heart into the aorta. The pump is connected via the one-way intake valve to a c~nnlll~ which is W 097/02850 PCTnL96/00045 inserted into the left ventricle of the heart through the aortic valve. When the internal vo1ume is e~p~n(le(l~ blood flows into the pump from the ventricle. The volume is then reduced, and the blood is ejected into the aorta through the outlet end. This pump is d~ci~ned to operate at a frequency of 600 to l,000 cycles per minute. Since the stroke volume of the pump is typically 5 only about 3-5 cc, these high cycie rates are needed in order to provide adequate perfusion.
In the Hemopump Cardiac Assist System, distributed by Johnson & Johnson Interventional Systems, a cannula cont~ining a special, minialure rotor pump me~l~A..;.~ is inserted into the aorta. The pump is driven by a drive unit outside the body, to pump blood continuously from the aorta into the rest of the arterial system, thereby suppl~omPntin~ the 10 heart's natural output rate. A system of this type is similarly described in U.S. patent 5,092,844, which is incorporated herein by reference. While continuous-flow devices are useful for short-term au~mentation or' cardiac output, it is believed that pulsatile pumps provide more effective long-term support. since they approximate more closely the natural pump action of the heart.

W O 97/02850 PCT~L96/00045 SUMMARY OF TEIE INVENTION
It is an object of the present invention to provide an intraventricular cardiac assist pump having a sufficiently large internal volume and improved valve structure, so that a~leqll~te pulsatile perfusion ofthe body may be dependably m~int~inPcl '' 5 In one aspect of the present invention, wherein the pump comprises a ~nmll~ one-way valve structures are provided in the sides of the cannula so as to reliablv control the alternate inflow and outflow of blood therefrom.
In plerel.~:d embodiments of the present invention, an intraventricular cardiac assist pump comprises a cannula, whose distal end is inserted through the aorta in~o the left ventricle, and a pulsatile drive unit, coupled to the cannula at the proximal end thereof. The cannula col..~lises an outer sheath, defining and enclosing an internal lumen, ha~ing at least one intake valve, adj~ct~nt to the cannula's distal end, and one or more outlet valves~ disposed radially along the length of the cannula. downstream from the intake valve. The pulsatile drive unit alternately reduces and increases the fluid pressure in the t~nn~ 'hen the pressure is 15 reduced, the at least one intal;e valve opens, while the one or more outlet vaives are closed, and blood flows through the intake valve into the lumen of the c:~nn~ The pressure in the cannula is then increased, causing the intake valve to close and the outlet valves to open, so that blood flows out of the lumen into the aorta.
In some preferred embodiments of the present invention, the pulsa~ile drive unit in~ es 2 0 a fluid reservoir, comprising first and second chambers, separated by a fle~ible diaphragm, each chamber havin, a fluid port. The fluid port of the first chamber is connected to the p-o~imal end of the c~nn~ , so that blood may flow between the chamber and the cannula. The fluid port of the second chamber is connected to a hydraulic drive, which alternately increases and decreases the pressure, and hence the volume, of a control fluid in the second chamber. The ?5 flexible diaphragm couples pressure changes from the second to the first chamber, without direct contact between the fluid in the second chamber and the blood in the first chamber, thereby controlling the flow of blood into and out of the lumen of the cannula, as described above. The use of the hydraulic drive enables substantially greater volumes of blood to be pumped, with greater efficienc~, than pneumatic pump drive mech~nismc that are commonly 3 0 used in other cardiac assist pumps known in the art.
It will be appreciated that in preferred embodiments of the present invention, as described above, the blood being pumped remains entirely inside the cannula and in the first chamber of the fluid reservoir connected thereto, without circulating substantially outside the body. Preferably, the cannula and fluid reservoir are disposable, intended for a single use, so as to reduce the likelihood of infection.
In p- efe. I t:d embodiments of the present invention, the cannula is capable of pumping at - least 50 cc, and preferably up to g0 cc of blood, in each stroke of the pulsatile drive unit. It will be appreciaLed, however, that depending on clinical requirements, the cardiac assist pump may - -W O 97/02850 PCT~LS.~ 4' be adjusted to pump a smaller volume in each stroke, for example 20 cc. The pulsatile dri-~e unit is preferably operated substantially at the rate of the human heart beat, and adjusted so that adequate perfusion of the arterial system is m~int~ine~ The drive is preferably syllclllolli~ed with the heart beat, so as to draw blood into the lumen of the cannula during systole and eject the blood into the aorta during diastole.
Alternatively, the drive may be counter-synchronized, so as to draw blood into the lumen during diastole and eject it during systole, or the drive may be operated asvnchronously, independent of the heart beat.
In preferred embodiments of the present invention, the cannula comprises a flexible, resilient tube having a rii~met~r in the range of l5-~0 French (5-lO mm). It is preferably inserted percutaneously throuoh the femoral artery, into the aorta. and then through the aortic valve into the left ventricle of the heart. Alternatively~ the cannula may be inserted elsewhere into the arterial system through a suitable surgical incision.
In some preferred embodiments of the present invenfion the at least one intake valve of the internal lumen ofthe cannula comprises a one-wa~ mechanic.~l flap valve or leatlet valve, as are known in the art. The at least one intake valve may comprise either an axial opening or one or more radial openin~s.
In some preferred embodiments of the present invention the one or more outlet valves similarly comprise mechanical flap valves, which open radialbt outward when tne pressure 2 0 inside the lumen of the cannula increases~ and close substan~iall- flush with the outer surface of the cannula when the pressure inside the lumen is reduced.
In other preferred embodiments of the present in- ention, the cannula contains arotatable inner sleeve, inside the outer sheath and radially enciosing the lumen. Preferably the sleeve extends along at least the portion of the len~th of the cannula along which the outlet valves are disposed. E.~ch of the one or more outlet valves comprises a first opening in the inner sleeve and a corresponding second openin, in the outer sheath. To open the outlet valve, the first and second openings are aligned, by suitably rotating the sleeve relative to the sheath.
To close the valve. the sleeve is counter-rotated, so as to disalign the first and second openings.
Preferably, the sleeve is constructed so that blood flo-vin(~ into the lumen causes a torque to be exerted on the sleeve, so that the sleeve rotates and the outlet valves are closed.
When the direction of flow of the blood in the lumen is reversed. the sleeve rotates back to its previous orientation, in which the outlet valves are open, and the blood can flow out.
Preferably the sleeve includes small wings or rotor blades fixed to its inner surface, for the purpose of converting the force of the blood flow into the torque e~certed on the sleeve.
Alternatively, an externally-driven mechanical rotation device is coupled to the sleeve and/or the sheath so as to effect the desired relative rotation to open and close the one or more outlet valves.

CA 0222649l l998-0l-07 W O 97/02850 PCTALg5/~C~1' In preferred embodiments of the present invention in which the cannula includes the rotatable inner sleeve, the at least one intake valve may comprise a merh~rlical flap or leaflet valve, as described above. Alternatively, the intake valve may comprise first and second openings, similar in function to the first and second openings of the outlet valves, except that 5 when the first and second openings of the outlet valves are aligned, those of the inlet valve are disaligned, and vice-versa.
In other preferred embodiments of the present invention, the cannula contains a sliding element, held inside the lumen, ~jacent to the distal end thereof, in such a manner that the sliding element can slide axially along the lumen but cannot rotate therein. The sliding element 0 inc~ 5 radial and axial openings through which blood can flow. The cannula further includes an axial opening, serving as an intake valve into the lumen, ~ Cçnt to the cannula's distal end, and one or more radial openings, serving as outlet valves from the lumen, along the length of the cannula proximal to the intake valve.
When the pressure inside the lumen is increased, the sliding element slides in Ihe distal 15 direction, therebv ~ng~(Sin(g and substan~ially closing the a~cial (intake) opening. When the sliding element is in this position, the radial openings of the sliding element are aligned with the ràdial openings in the (~nn~ , SO that blood may flow out of the lumen.
When the pressure inside the lumen is reversed, i.e., reduced to a negative plCS:iUlC
relative to the blood pressure outside the lumen, the sliding element slides proximally, away 2 o from the distal end of the cannula. so that blood may flow into the lumen through the reopened axial openings of the cannula and the sliding element. In the proximal position, the radial openings of the sliding element are disaligned with the radial openings in the c~nn~ so that the outlet valves are effectively closed.
Alternatively, in other preferred embodiments of the present invention, which operate 25 similarly tO those just described. the cannula includes one or more radial intake openings, to serve as intake valves in place of the axial opening described above. The sliding element similarly includes radial intake openings, in place of the axial openings described above. When the pressure inside the lumen is reversed, i.e., reduced to a negative pressure relative to the blood pressure outside the lumen, the radial intake openings in the sliding element align with 30 the radial intake openings in the lumen, so that blood may flow into the lumen. When the pressure inside the lumen is increased, the intake vah/es close, and the outlet valves open, as described above.
In still other preferred embodiments of the present invention, the outlet valves of the cannula comprise radial openings along the length thereof, which are covered and closed by a 3 5 flexible, elastic outer sheath, preferably made of biocompatible rubber. The sheath is preferably held in place bv a squeeze ring along a portion of its length. The at least one intake valve may comprise a mechanical flap, leaflet or other valve type described above or otherwise known in the art.

W O 97/02850 PCT~L9~/~CC'5 Alternatively, the at least one intake valve may similarly comprise a flexible, elastic inner sheath and operate in a manner similar to the outlet valves, as will be described below.
Normally, the elasticity of the outer sheath covering the outlet valves causes it to cling radially to the outer surface of the c~nn~ thereby closing the outlet valves. When the 5 pressure inside the lumen of the cannula is increased, however, the pressure of the blood exerts an outward force on the sheath through the radial openin~,s. This force causes the sheath to stretch out~ards, allo-~ing the blood to flow out ofthe lumen.
There is therefore provided, in accordance with a preferred embodiment of the present invention, a cardiac assist pump, including:
a ç~nn~ including an outer sheath, which defines and encloses a lumen therein, the cannula having a distal end and a proximal end, wherein the cannula is inserted through the aorta of a subject so that the distal end is inside a ventricle of the heart of the subject;
at least one intalie valve~ adjacent to the distal end of the cannula, through which blood enters the lumen from fne ventricle:
at least one o~let valve disposed radially alon~g, the sheath of the c~nn~ through which blood e.Yits the lumen into the aorta:
a fluid reservoir. having a ~ariable fluid volume, connected to the proximal end of the c~nn~ such that blood mav flow between the lumen and the rese~voir; and a pump drive. c;)upled to the fluid reservoir and controllino the fluid volume in said 2 O reservoir, wherein the pump drive alternatelv increases and decreases the fluid volume in the reservoir to produce a pulsatile pumping"~ction of blood through the cannula.
Preferablv, the reservoir has a minimum and a ma~imum volume, the difference therebetween defining a reser~oir stroi;e volume, wherein the cardiac assist pump has a stroke 25 volume substantially derined b~ the stroke volume of the fluid reservoir. Preferably, the pump has a maximum stroiie volume or' a~ least ~0 cc, and more preferablv, appro~cimately 80 cc.
Preferablv, the pump drive is hydraulically coupled to the fluid reservoir and is synchronized with the beating ot'the heart.
Preferably, the intal;e and outle~ valves include at least one one-way valve. Additionally 30 or alternatively, the intaiie and outlet valves include at least one mechanical flap valve, and/or the intake valve includes a leaflet valve.
Additionallv or alternativelv, the pump includes a rotatable inner sleeve, situated within the lumen, ~vherein rotation of the inner sleeve relative to the sheath opens and shuts at least one of the intake and outlet valves. Preferably, at least one of the intake and outlet valves 35 includes a first radial openin<J, in the sheath and a second, correspondino, radial opening in the inner sleeve, wherein rotation of the inner sleeve relative to the sheath causes the at least one valve to open by bringing the respective first and second radial openings substantially into mutual alignment. Preferabiy, a torque-coupling device is coupled to the inner sleeve, which -W O 97/02850 PCT~L96/00045 device preferably includes winglets fi~ced to the sleeve and causes the inner sleeve to rotate in response to blood flow in the lumen.
Alternatively or additionallv, the pump inf~lud~-s an inner sliding e!ement, situated within the lumen, which moves axially inside the lumen to alternately open and close the intake and 5 outlet valves. Preferably, at least one of the intake and outlet valves includes a first radial opening in the sheath and a second~ corresponding radial opening in the inner sliding element, ~ and axial movement of the sliding element in the lumen causes the at least one valve to open by bringing the respective first and second radial openings thereof s~ t~nti~lly into mutual ~lionmtont Alternatively or additionallv, the at least one intake valve includes an axial opening in the ç~nnul~ and the inner slidino element moves axially away from the axial opening in the cannula to open the intake valve.
Further alternatively or additionally, the pump includes an elasric outer sleeve, which clings elastically to an outer, radial surface of the cannula to ciose the outlet valves, wherein the ; 5 elastic outer sleeve st}etches outw-ard in response to a pressure of the blood inside the c~nn thereby opening the outlet valves.
Moreover, alternativelv or additionally, the pump includes an elaslic inner sleeve, which clings elastically to an inner, radial surface of the cannula to close the intake valves, wherein when pressure of the blood inside the cannula is reduced, the elastic inner sleeve deforms inward in response to pressure of the blood outside the c~nn~ there~v opening the intake valves.
There is further provided~ in accordance with a preferred embodiment of the present invention, a method for augmentino the blood output of the heart, includino:
connecting a cannula, having distal and proximal ends and having intake and outlet valves, to a fluid reservoir at the pro~cimal end of the cannula;
inserting the cannula throuoh an artery, so that the distal end of rhe cannula is inside the left ventricle of the heart;
drawing blood from the ventricle, through the intake valve of the cannula and into the fluid reservoir, by reducing a fluid pressure in the reservoir; and ejecting the blood from the reservoir through the outlet valve or the cannula and into the artery, by increasin, the fluid pressure in the reservoir.
Preferably, drawing blood and ejecting blood are performed repeatedly, in alternation, wherein in each alternation, between 20 and 80 cc of blood are drawn and ejected. Preferably drawing and ejectin~3 blood include applying hydraulic forces to the reservoir.
Preferably, the method includes sensing a heart beat signal, wherein drawing blood and ejecting blood comprise drawing and injecting blood in synchrony with the heart beat, wherein blood is drawn either during systole or during diastole.
Preferably, this method is carried out using a cardiac assist pump as described above.

W O 97/02850 PCT~L96/00045 There is further provided, in accordance with a preferred embodiment of tke present invention, a one-way valve for use in a heart-assist device, which valve incl~ldes:
an outer sheath, defining an enclosing a lumen therein, and inclu-iinv a first radial opening;
an inner sleeve, rotatably held inside the outer sheath, and incl~ltling a second radial opening, which is alignable with the first radial opening by rotation of the sleeve, such that when the first and second radial openings are mutually aligned, the valve is open; and a torque coupling device, coupled to the inner sleeve, wherein in response to flow of a fluid in the lumen in a first flow direction, the torque lC coupling device causes the sleeve to rotate in a first rotational direction, therebv altering the alignment ofthe first and second radial openings.
Preferably, in response to flow of the fluid in the lumen in a second flow direction, generally opposite to the first flow direction, the torque couplin~r device causes the sleeve to rota~e in a direction opposite to the first rotational direction. Preterablv rotation of the sleeve in the firs~ rotational direction causes the valve to open. and rotation of the sleeve in the opposite direction causes the valve to close.
Preferably, the torque coupling device includes winglets. ~i~ed to the sleeve.
There is also provided, in accordance with a preferred embodiment of the presentinvention, a one-way valve assemblv. including an inta};e ~alve and an outlet valve. for use in a 2 0 heart-assist device, w-hich assemblv includes:
an outer sheath~ defining and enclosing a lumen therein. and includin~ a first intake opening and a first outlet opening; and an inner sliding element, held inside the lumen and a.Yially movable therein, and including a second intaL;e opening and a second outlet opening. respectivelv alignable with the first intake opening and the frst outlet opening by axial movemen~ of the sliding element, such that when the slidina element is in a first aYial position, the first and second intake openings are aligned, so that the intal;e valve is open, and when the sliding element is in a second axial position, the first and second outlet openings are aligned, so that the outlet valve is open, wherein in response to changes of a fluid pressure inside the lumen, the inner sliding 3 0 element moves a.Yially in the sheath between the first and second axial positions.
Preferably, for any position of the sliding element intermedi~e the first and second axial positions, no more than one of the intake and outlet valves is open.
Preferably, in response to an increase of the fluid pressure inside the lumen, the inner sliding element moves to the second axial position, thereby opening the outlet valve, and in 3 5 response to a decrease of the fluid pressure inside the lumen, the inner sliding element moves to the first aYi~l position, thereby opening the intake valve.
There is additionally provided. in accordance with a preferred embodiment of thepresent invention, a one-wav valve for use in a heart-assist device, w hich valve includes:

-W O 97/02850 PCT~196/00045 an outer sheath, defininsg and enclosing a lumen therein, and including a radial opening;
and an elastic outer sleeve, which clings elastically to an outer, radial surface of the sheath to cover the radial opening, thereby closing the valve, wherein in response to an increase of a fluid pressure inside the lumen, the outer sleeve stretches outward, thereby openin~3 the valve.
Moreover, in accordance with another preferred embodiment of the present invention, there is provided a one-way valve for use in a heart-assist device, said valve including:
an outer sheath, defining and enclosing a lumen therein, and including a radial opening;
l 0 and an elastic inner sleeve, which clings elastically to an inner, radial surface of the sheath to cover the radial opening, thereby closing the valve, wherein in response to a decrease of a fluid pressure inside the lumen, the inner sleeve deforms inward. thereby opening the valve.
Preferabiy, such one-way valves including an elastic sleeve also include a retaining rin_, circull~r~ Liallv engaging a portion of the sleeve, which ring holds the sleeve in place relative to the sheath.
The present invention will be more fully understood from the following detailed description of ~he preferred embodiments thereof. taken together with the drawings in which:

CA 0222649l l998-0l-07 W O 97t02850 PCT~L~5/~

BRIEF DESCR~PTION OF THE DRAWINGS
Fig. 1 is a schematic, sectional repl~senLalion of a cardiac assist pump, in accordance with a preferred embodiment of the present invention;
Fig. 2A is a schematic representation of a cannula in accordance with a ~I~Çe;ll~d embodiment of the present invention, illustrating the insertion of the cannula into the heart;
Fig. 2B is a schematic representation of a cannula in accordance with another pl~rc:lled embodimen~ of the present invention, illustrating the insertion of the cannula into the heart;
Fig. ~ is a schematic~ sectionah isometric 1 ep~ ese,ltaLion of a valve assembly in accordance with a preferred embodiment of the present invention;
Fig. 4A is a sectional representation of a valve assemblv in accordance with a preferred embodiment of the present invention, including intake and outlet valves, shown in a first position in which the intal;e ~alves are open and the outlet valves are closed;
Fig. ~B is a sectional representation of the valve assemblv of Fig. ~A. shown in a second posilion in which the inta~;e valves are closed and the outlet valves are open;
Fig SA is a sectional representation of a valve assembly in accordance with another preferred embodiment ot' the present invention, including intake and outlet valves, shown in a first position in which the intal;e v alves are open and the outlet valves are closed;
Fig. SB is a sectional re?resentation of the valve assembly of Fig. 5.~, shown in a second 2 0 position in which the intalie v alves are closed and the outlet vaives are open;
Fig. 6A is a schema~ic~ partlv sectional representation of a valve assembly in accordance with a preferred embodiment ot' the present invention, shown in a first position in which the valves are closed;
Fig. 6B is a schematic. partlv sectional representation of the valve assembly of Fig. 6A, 2 5 shown in a second position in ~vhich the valves are open;
Fig. 7A is a schematic. sectional representation of another valve assembly in accordance with a preferred embodiment of the present invention~ shown in a first position in which the valves are closed; and Fig. 7B is a schematic~ sectional representation of the valve assemblv of Fig. 7A, shown in a second position in tvhich the valves are open.

W O 97/02850 rCT~ .'C_15 DETAILED DESCR~PTION OF PREFERRED EMBOD~ENTS
Reference is now made to Fig. 1, which is a schematic, sectional ~ s~ nn of a cardiac assist pump system lg, in accordance with a preferred embodiment of the present invention. The system comprises an intra-aortic cannula 20, having an outer sheath 22, which defines and encloses an inner lumen 24. Preferably cannula 20 has a r7i~m~rer in the range of 15-30 French (5-10 mm) and is made of flexible, resilient material, for example, polyurethane reinforced with stainless steel wire, so that it may be inserted into and passed through major arteries of the human body. Cannula 20 further inciudes an intake valve '6, preferably axially disposed, ~(ijacr nt to its distal end 28, and one or more outlet valves 30, radially disposed along sheath 22 of the cannula. The intake and outlet valves are preferably made of stainless steel or stiffplastic material, such as polycarbonate, or other suitable materials l;no~n in the art.
Intake valve 76 and outlet valves 30 are preferably one-way valves. so that blood may flow into and out of cannula 20 substantially only in a sin~le direction: ente7ing through intake valve 6 and exiting through ou71et valves 30 (corresponding to the direction of blood flow in the body, as will be described below). In the preferred embodiment of the present invention shown in Fig. 1, the intake and outlet valves comprise mechanical flap ~aives, which rotate about respective hin~es ~4 and 36 to open and shut as desired. A though hinge 34 of intake valve ~6 is shown to be located along a central axis of the valve, it mav similarly be located at one side of the valve, like hinges ~6 of outlet valves 30.
Alternatively, intake val~,e 26 may comprise any other suitable tvpe of one-way valve, for example a leaflet valve. Such leaflet valves are known in the art for use in heart-assist devices, as described, for example~ in a PCT patent application entitled. "~lethod for Producing Heart Valves and Heart Valves Produced by the Method," filed on even d~te with the present application, which is assigned to the assignee of the present invention and ~~hose disclosure is ? 5 incorporated herein by reference.
In other preferred embodiments of the present invention, as w,ill be described below, other types of intake and outlet valves may similarly be used.
Fig. ~A shows, schematically, the use of cannula 20 in a human heart ~0. Preferably the cannula is inserted percutaneously~ through an incision into a peripheral arterv ~2, for example the femoral artery, and passed upstream through aorta 44 into left ventricle '6 of heart 40. The method of insertion is substantially similar to methods for insertion of other types of cardiac cz7nnl71~e known in the art. T7ne len~th of cannula 20 is preferably approximately 60 cm, which is generallv sufficient so that when distal tip 28 is positioned in ventricle d.6~ proximal end 32 remains outside the body, adjacent to the incision. Alternatively, the cannula may be inserted 3 5 surgically through a suitable incision elsewhere in the arterial system, and in such cases may be shorter than 60 cm, depending on the distance from the incision to the heart.
~ Once cannula 20 is in place. intake valve 26 is opened, and blood flows from ventricle 46 into lumen 24. Preferably outlet valves 30 are kept closed while the blood fills the lumen.

W O 97/02850 PCTAIS6.~
Proximal end 32 may be temporarily opened, to vent out air or fluid that was inside cannula 20 before its insertion. Then intake valve 26 is closed and outlet valves 30 are opened, so that the blood may flow out of the lumen and into aorta 44.
As illustrated in Fig. 1, intake valve 26 and outlet valves 30 preferably open and shut in 5 response to pressure exerted through pump system 18 to cannula ~0, in the following manner.
Proximal end 32 of cannula 20 is connected to a first chamber 50 of a fluid reservoir 52 through a first fluid port 54. Fluid reservoir 5~ further includes a second chamber 56, which is separated from first chamber 50 by a flexible diaphragm ~8. Diaphragm 58, which is preferably made of flexible pol,vurethane, deforms to alter the respective volumes of chambers 50 and 56, 10 so as to substantially equalize the fluid pressures in the t~vo chambers, but prevents minolino of the fluids in the first and second chambers.
Second chamber ~6 preferably contains a substantiall- incompressible liquid, such as water or, alternatively. anv other suitable fluid, such as normal saline solution. Chamber 56 is coupled via a second fluid port 60 throucJh a tube 6~ to a pump drive 64. .~ piston 66 in pump 15 drive 64 moves alternately up and do-vn to correspondingly increase and decrease the fluid pressure in reservoir 5~. thereby pumping blood out of and into lumen ~4.
~ It will be appreciated that the maximum volume of blood that may be pumped in a single stroke of piston 66 is roughly determined by the volume of reser~oir ~0. Preferably this maximum single strol;e pumping volume is at least 50 cc~ and more preferablv up to 80 cc, 20 although piston 66 ma!- also be operated with a shorter stro~e to pump a smaller volume of blood if desired. Preferably, the stroke is adjusted so that when pump drive 64 is operated at or about the heart's natural rate~ sufficient blood can be pumped to perfuse substantially all of the person's body.
It will further be appreciated that blood mav enter cannula ~0 and flow into first 25 chamber 50 only up to diaphragm ~ ~rO blood flo~s through tubing 6~ or into pump drive 64. Preferablv, cannula ~0 and reservoir 5'' are disposable and made for single use only, to prevent transfer of infections and contamination.
Pump drive 64 is driven by a servo mechanism 6~ under the control of an internalcomputer 70~ which regulates the rate and stroke volume of piston 66. Preferably, computer 70 30 receives physiological si_nal inputs, such as ECG and blood pressure signals, and uses these signals in optimally controlling pump drive 64, preferably to dri~e piston 66 at the rate of the heart beat.
Preferably, computer 70 adjusts the delay of the piston stroke relative to the systolic stroke of the heart. This delay may be adjusted so that c~nnula 0 pumps blood out 3 5 synchronously with the heart's systole; countersynchronously, during diastole; or at any suitable phase therebetween. Alternatively, the rate of piston 66 may be set to be independent of the heart rate, for example in order to rn~int~in steady perfusion during arrhythmia or fibrillation.

O 97102850 PCTnL96/00045 Fig. 2B illustrates, srh~m~tically, an alternative preferred embodiment of the present invention, in which cannula 20, shown inserted into human heart 40, has a plurality of intake valves 26, radially disposed along the length of the cannula. Radial intake valves 26 may be flap valves, like valves 30 shown in Fig. 1 but opening inward, or one-way valves of other types described below or otherwise known in the art. It will be appreciated that the cannula shown in Fig. 2B functions in a substantially identical manner to that described above and illustrated in Figs. 1 and 2A.
Fig. 3 illustrates sch~ tically an alternative construction of outlet valves 30, in accordance with another preferred embodiment of the present invention. As shown in Fig. 3, cannula 20 contains an inner sleeve 72, rotatably mounted inside outer sheath 22 and enclosing lumen 24. Inner sleeve 72 extends axially along at least the portion of cannula 20 in~ ling outlet valves 30. Each outlet valve 30 comprises an outer opening 74 in outer sheath 22 and an inner openin_ 76 in inner sleeve 7'7. To open outlet valves 30, inner sleeve 72 is rotated so that inner openings 76 are aligned with outer openings 74. When the inner and outer openings are disaligned, the valves are closed.
Preferably, a plurality of winglets ~0 are fixed to the inner surface of sleeve 7Z and cause the sleeve ~o rotate in response to blood flow through the lumen. When piston 66 is drawn back in pump drive 64, as shown in Fig. 1, blood will flow through lumen 24 substantially in the direction indicated in Fig. 3 by an arrow S2. The force of this flow against winglets 80 exerts a torque on sleeve 72, causing it to rotate in a clockwise direction, as indicated in the figure bv an arrow 84. thus closing outlet valves 30. When a desired volume of blood has been drawn into reservoir 50, piston 66 is pushed forward, so that blood flows in the lumen in the direction opposite to arrow 82. Sleeve 7~ then rotates in the counterclockwise direction, so that outlet valves 30 open.
Alternatively, sleeve 7~ or sheath 22 may be coupled proximally to a me~h~nic~l rotation drive, of any suitable type known in the art, so as to effect the desired relative rotation to open and close outlet valves 30 In the preferred embodiment of the present invention utilizing the outlet valves shown in Fig. 3, intake valve ''6 (not shown in the figure) may be a mechanical flap valve or leaflet valve, as described above. Alternatively, the intake valve may comprise a pair of alignable openings in sheath 22 and sleeve 7'', which open and shut by the rotation of the sleeve relative to the sheath, in a manner similar to the operation of openings 74 and 76. The sheath and sleeve are constructed, however, so that when the pair of intake valve openings are aligned, to open intake valve 26, openings 74 and 76 are rlic~ligne~l, to close outlet valves 30. Similarly, when the outlet valve openings are aligned, the intake valve openings are ~liC~ligne~l, and thus shut.
Figs. 4A and 4B show still another preferred embodiment of the present invention, in which a sliding element 90 inside lumen 24 alternately opens and shuts intake valve 26 and outlet valves 30. Preferably, at least one axial tongue 91, fixed on the inner surface of cannula WO 97/02850 PCT~lg6/00045 sheath 2, engages a m~chino groove 93 on the outer surface of sliding element 90, so that the sliding element may move up and down inside the lumen, but may not rotate about its axis.
In Fig. 4A, the pressure in lumen 24 has been reduced below the blood pressure at the proximal end of cannula 20, preferably by means of pump drive 64, as described above with 5 reference to Fig. 1. The relatively greater pressure of the blood at the distal end of cannula 20, inside the left ventricle of the heart, forces sliding element 90 upward, opening intake valve 26.
Blood flows into lumen 24 through valve 26, via sliding element front openings 92.
Disalignment of sliding element side openings 94 with cannula radial openings 96 closes outlet valves 30.
In Fig. 4B, the pressure in lumen 24 is increased, forcing sliding element 90 downward and closing intake valve ~6. Openings 94 and 96 are now mutually ali2ned, thus opening outlet valves 30, through which blood flows out into the aorta.
Figs. 5A and SB illustrate another preferred embodiment of the present invention, substantially similar in operation to that shown in Figs. 4A and 4B. In Figs. SA and SB, however, intake valves 26 are radiall~v disposed along sheath ~'' of cannula ~0, like outlet valves 30. A sliuing stopper element 97 inside lumen '74 comprises at least two sets of radial openings: intake openin~Js ~ and ou~let openings 99. In Fig. 5A, increased pressure inside lumen 24 causes sliding element 97 to move downward, so that outlet openings 99 are aligned to open outlet valves i0. In Fig. ~B, reduced pressure in the lumen causes the sliding element to move upward, ali~ning intal;e openings 98 with intake valves 26. A slot 100 in sliding element 97 engages a pin 101 ~i~ed in sheath ''2~ so as to prevent rotation of the sliding element. Other methods of preventing rotation, as are known in the art, may also be used.
Figs. 6A and 6B illustrate still another preferred embodiment of the present invention, in which a fle~ible, elastic outer sleeve 102 covers and closes radial openings 104 in sheath 22 of cannula ''0. which openings serve as outlet valves 30. Intake valve ~6 (not shown in these figures) mav comprise a mechanical ~lap valve or leaflet valve or any other suitable type described herein and/or l;no-~n in the art. Sleeve 102, which is preferably made of latex, silicone, or other biocompatible rubber, is preferably held in place by squeeze ring 106.
Alternatively, sleeve 10'' mav be glued in place or otherwise secured.
In Fig. 6A, the pressure in lumen ''4 has been reduced so that blood may be drawn in through the intake valve, as described above with reference to Fig. 1 The elasticity of sleeve 102 causes it to clin~7 radially to the outer surface of cannula '~0, so that outlet valves 30 remain closed.
In Fig. 6B, however, the pressure of the blood inside lumen 24 has been increased. This pressure exerts an outward force on sleeve 10'7 through openings 104, causing the sleeve to stretch outward, and thus opening outlet valves 30.
As illustrated in Figs. 7A and 7B, in a further preferred embodiment of the present invemion, a flexible, resilient inner sleeve 110 covers and closes radial openings 112 in sheath W O 97/02850 PCT~196/00045 22 of cannula 20, which openings servé as intake valves 26. Sleeve 110 preferably co,.,~u,ises biocompatible rubber, as described above, and is preferably held in place by a substantially rigid expander ring 114. Alternatively, sleeve 110 may be glued in place or otherwise secured.
When the pressure inside lumen ~4 is greater than the blood pressure outside cannula 20, sleeve 110 is pressed outwards, closing valves 26, as shown in Fig. 7A. When the pressure inside the lumen is reduced, the pressure of the blood outside cannula 20, exerted through openings 112, causes sleeve 110 to deform inward, as shown in Fig. 7B, opening valves ~6.
It will be appreciated that the preferred embodiments described above are cited by way of example, and the full scope of the invention is limited only by the claims.

Claims

1. A cardiac assist pump, comprising:
a cannula, comprising an outer sheath, which defines and encloses a lumen therein, said cannula having a distal end and a proximal end, wherein 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;
at least one intake valve, adjacent to the distal end of the cannula, through which blood enters the lumen from the ventricle;
at least one outlet valve, disposed radially along the sheath of the cannula, through which blood exists the lumen into the aorta;
a fluid reservoir having a variable fluid volume, connected to the proximal end of the cannula, such that blood may flow between the lumen and the reservoir; and a hydraulic pump, coupled to the fluid reservoir and controlling the fluid volume in said reservoir, wherein the pump alternately increases and decreases the fluid volume in the reservoir to produce a pulsatile pumping action of blood through the cannula.

2. A cardiac assist pump in accordance with claim 1, wherein the fluid reservoir has a minimum and a maximum fluid volume, the difference therebetween defining a reservoir stroke volume, and wherein the cardiac assist pump has a stroke volume substantially defined by the reservoir stroke volume.

3. A cardiac assist pump in accordance with claim 2, having a maximum stroke volume of at least 50 cc.

4. A cardiac assist pump in accordance with claim 3, having a maximum stroke volume of approximately 80 cc.

5. A cardiac assist pump in accordance with any of the preceding claims, wherein the pump mechanism is synchronized with the beating of the heart.

6. A cardiac assist pump in accordance with any of the preceding claims, wherein the intake and outlet valves comprise at least one one-way valve.

7. A cardiac assist pump in accordance with any of claims 1-5, wherein the intake and outlet valves comprise at least one mechanical flap valve.

8. A cardiac assist pump in accordance with any of claims 1-5, wherein the intake valve comprises a leaflet valve.

9. A cardiac assist pump in accordance with any of claims 1-5, and comprising a rotatable inner sleeve, wherein rotation of the inner sleeve relative to the shear opens and shuts at least one of the intake and outlet valves.

10. A cardiac assist pump in accordance with claim 9, wherein the at least one of the intake and outlet valves comprises a first radial opening in the sheath and a second, corresponding radial opening in the inner sleeve, and wherein rotation of the inner sleeve relative to the sheath causes the at least one valve to open by bringing the respective first and second radial openings thereof substantially into mutual alignment.

11. A cardiac assist pump in accordance with claim 9 or claim 10, and comprising a torque-coupling device, coupled to the inner sleeve, which device causes the inner sleeve to rotate in response to blood flow in the lumen.

12. A cardiac assist pump in accordance with claim 11, wherein the torque coupling device comprises winglets fixed to the sleeve.

13. A cardiac assist pump in accordance any of claims 1-5, and comprising an inner sliding element situated within the lumen, which element moves axially inside the lumen to alternatively open and close the intake and outlet valves.

14. A cardiac assist pump in accordance with claim 13, wherein at least one of the intake and outlet valves comprises first radial opening in the sheath and a corresponding radial opening in the inner sliding element, and wherein the axial movement of the sliding element in the lumen causes the at lest one valve to open by bringing the respective first and second radial openings thereof substantially mutual alignment.

15. A cardiac assist pump in accordance with claim 13 or claim 14, wherein the at least one intake valve comprises an axial opening in the cannula, and wherein the inner sliding element moves axially away from the axial opening in the cannula to open the intake valve.

16. A cardiac assist pump in accordance with any of claims 1-5, and comprising an elastic inner sleeve, which clings elastically to an inner, radial surface of the cannula to close the intake valves.

17. A cardiac assist pump in accordance with claim 16, wherein the elastic inner sleeve deforms inward in response to a pressure of the blood outside the cannula, thereby opening the intake valves.

18. A cardiac assist pump in accordance with any of claims 1-5, 16 or 17, and comprising an elastic outer sleeve, which clings elastically to an outer, radial surface of the cannula to close the outlet valves.

19. A cardiac assist pump in accordance with claim 18, wherein the elastic outer sleeve stretches outward in response to a pressure of the blood inside the cannula, thereby opening the outlet valves.

20. A cardiac assist pump in accordance with any of the preceding claims wherein the reservoir comprises an movable wall and wherein the hydraulic pump is operative to cause the wall to move such that the volume of the reservoir is changed.

21. A cardiac assist pump in accordance with claim 21 wherein the movable wall is a elastic wall.

22. A method for augmenting the blood output of the heart, comprising:
connecting a cannula, having distal and proximal ends and having intake and outlet valves, to a fluid reservoir at the proximal end of the cannula;
inserting the cannula through an artery, so that the distal end of the cannula is inside the left ventricle of the heart;
applying hydraulic forces to the reservoir such that:

blood is drawn from the ventricle, through the intake valve of the cannula and into the fluid reservoir, by reducing a fluid pressure in said reservoir; and blood is elected from the reservoir through the outlet valve of the cannula and into the artery.

23. A method in accordance with claim 22, wherein drawing blood and ejecting blood are performed repeatedly, in alternation.

24. A method in accordance with claim 23 wherein in each alternation, between 20 and 80 cc of blood are drawn and ejected.

25. A method in accordance with any of claims 22-24, and comprising sensing a heart beat signal, wherein drawing blood and ejecting blood comprise drawing and injecting blood in response to the heart beat signal.

26 A method in accordance with claim 25, wherein drawing blood into the cannula comprises drawing blood during systole.

27. A method in accordance with claim 25, wherein blood into the cannula comprises drawing blood during diastole.

28. A method in accordance with any of claims 22-27, wherein the reservoir comprises an movable wall and wherein applying hydraulic forces causes the movable wall to move such that the volume of the reservoir is changed.

29. A method in accordance with any of claim 22-28, wherein the reservoir comprises an elastic wall and wherein applying hydraulic forces causes the elastic wall to move such that the volume of the reservoir is changed.

30. A one-way valve for use in a heart-assist device, said valve comprising:
an outer sheath, defining an enclosing a lumen therein, and comprising a first radial opening;

an inner sleeve, rotatably held inside the outer sheath, and comprising a second radial opening, which is alignable with the first radial opening by rotation of the sleeve, such that when the first and second radial openings are mutually aligned, the valve is open; and a torque coupling device, coupled to the inner sleeve, wherein, in response to flow of a fluid in the lumen in a first flow direction, the torque coupling device causes the sleeve to rotate in a first rotational direction, thereby altering the alignment of the first and second radial openings.

31. A one-way valve in accordance with claim 30, wherein in response to flow of the fluid in the lumen in a second flow direction, generally opposite to the first flow direction, the torque coupling device causes the sleeve to rotate in a direction opposite to the first rotational direction.

32. A one way valve in accordance with claim 30 or claim 31, wherein rotation of the sleeve in the first rotational direction causes the valve to open and rotation of the sleeve in the opposite direction causes the sleeve to rotate in a direction opposite to the first rotational direction.

33. A one-way valve in accordance with any of claims 30-32, wherein the torque coupling device comprises winglets, fixed to the sleeve.

31. A one-way valve assembly, including an intake valve and an outlet valve, for use in a heart-assist device, said assembly comprising:
an outer sheath, defining and enclosing a lumen therein, and comprising a first intake opening and a first outlet opening; and an inner sliding element, held inside the lumen so as to be axially movable therein, and comprising a second intake opening and a second outlet opening, respectively alignable with the first intake opening and the first outlet opening by axial movement of the sliding element, such that when the sliding element is in a first axial position, the first and second intake openings are aligned, the intake valve is open, and when the sliding element is in a second axial position, the first and second outlet openings are aligned, the outlet valve is open, wherein in response to a change of a fluid pressure inside the lumen, the inner sliding element moves axially in the sheath, between the first and second axial positions.

35. An assembly in accordance with claim 34, wherein for any position of the inner sliding element intermediate the first and second axial positions, no more that one of the intake and outlet valves is open.

36. An assembly in accordance with claim 34 or 35, wherein in response to an increase of the fluid pressure inside the lumen, the inner sliding element moves to the second axial position, opening the outlet valve.

37. An assembly in accordance with claim 36, wherein in response to a decrease of the fluid pressure inside the lumen, the inner sliding element moves to the first axial position, opening the intake valve.