GB2545750A

GB2545750A - An implantable blood pump

Info

Publication number: GB2545750A
Application number: GB1522944.6A
Authority: GB
Inventors: Nair Sukumaran; Husein Harji Bashir
Original assignee: Cambridge Reactor Design Ltd
Current assignee: Cambridge Reactor Design Ltd
Priority date: 2015-12-25
Filing date: 2015-12-25
Publication date: 2017-06-28
Also published as: GB201522944D0

Abstract

A blood pump 1 suitable for implantation within a conduit, arranged to be mounted to and extend through either an aperture of the aortic or pulmonary annulus. The pump 1 has a casing 2, 3 defining an inlet 1A and outlet 1B, a pump element 6 and a driving mechanism 8; a support for supporting the pump to wall of a conduit; and an electrical lead that passes out of the casing through the support or through the casing at an inlet side of the support. This allows the electrical lead to extend out through the blood vessel without contacting blood. The support may comprise apertures 3C for a suture fastener, and may comprise a protrusion or collar 3B which extends laterally to the direction of flow. The pump element may be an impeller 6 with magnets 7, driven by the coil winding 8. The driving mechanism may be isolated from the fluid. A method of implanting the blood pump is also provided.

Description

An Implantable Blood Pump

The present invention relates to a pump, and in particularly but not exclusively an implantable blood pump. It also relates to a heart pump forming part of a ventricular assist device and to a method of implanting a heart pump forming part of a ventricular assist device.

Ventricular assist devices (VADs) are used to support heart function in patients with poor functional capacity. The VAD draws blood from either the left or right ventricle of the heart and pumps it into either the aorta or pulmonary artery.

Figure 4 of US4957504 illustrates a typical arrangement of known VAD systems in which a hole is made through the apex of the left ventricle wall for insertion of a tube into the ventricular cavity. Blood is pumped out of the ventricle, through an extra-vascular conduit to the aorta. VAD shave also been used for the right ventricle; however, because of the differing shape of the right ventricle, there is a tendency for the interventricular septum, which separates the left and right ventricles, to be drawn against and obstruct the inlet of the pump. This may lead to a low output / flow state with frequent malfunctioning of the VAD. This phenomenon could also increase the risk of thrombosis at the either the VAD pump inlet or within the pump itself. A solution is to implant a blood pump intraventricularly to draw blood from the ventricle and though the ventricle opening, which is usually guarded by either the aortic or pulmonary valve, into the aorta or pulmonary artery. KR20140139861, US2013066421, US2014128967, US2006195004 & US2010249489 relate to blood pumps that sit at least in part in the exit of the ventricle, adjacent to or occupying the position of the pulmonary or aortic valve. A problem with the pumps disclosed in these documents is that when implanted, the electrical lead that supplies power to the pump is in contact with the blood within the artery giving rise to a perceived clotting risk and an increased risk of infection.

For the above reasons, there is currently no known commercially available ventricular assist device that is suitable for long term use, i.e. several years, to assist the right ventricle in clinical practice.

The present invention was conceived to provide a VAD that can be used for long term use in either the left or right ventricle whilst minimising the risk of clotting.

Although initially conceived for a very specific use as a blood pump forming part of a VAD, it is foreseen that the invention is more broadly applicable to any pump adapted to be located within the conduit carrying the fluid to be pumped.

According to a first aspect of the invention there is provided a pump adapted for operation within a fluid carrying conduit to impel fluid through the conduit, the pump having: a casing defining an inlet and an outlet, the casing housing a pump element and a driving mechanism to drive the pump element to impel fluid through the conduit; a support for supporting the pump to a wall of the conduit; and further comprising an electrical lead that passes out either through the support or through an outer wall of the casing at an inlet side of the support, for passage through the conduit wall to a power source to supply power to the drive mechanism.

Preferably the electrical lead passes through the support for passage through the conduit wall to a power source to supply power to the drive mechanism.

The invention thereby allows the electrical lead to pass out of the conduit without making contact with the fluid being carried within the conduit. Where the pump is used as a blood pump, the invention provides the benefit that the electrical lead need not come into contact with blood.

Where used as part of an intraventricular assist device, the support may be arranged for supporting the pump against an aortic annulus or pulmonary annulus; the electrical lead passing through the aortic or pulmonary annulus. By forming a liquid tight interface between the annulus and the support and/or the outer wall of the casing at the inlet side of the support, the electrical lead avoids coming into contact with blood flow.

To form a fluid free path for the electrical lead out of the cavity, it is preferred that the support defines a supporting surface, possibly an outwardly radially facing supporting surface, which when the pump is operated within the conduit, sits against, and preferably to form a liquid tight seal with, an inner surface of the conduit wall; the electrical lead passing through the supporting surface.

It is preferred that the supporting surface provides substantially continuous circumferential contact, and more favourably a substantially continuous circumferential liquid tight seal against the inner surface of the conduit wall around the casing. As well as securely anchoring the pump to the cavity, this also inhibits back flow of fluid from the outlet back towards the inlet.

To this end it may be preferable that the support comprises a protrusion that extends radially away from the axis of fluid flow through the conduit, i.e. so as to extend towards the wall of the conduit, and more preferably comprises a substantially circumferentially continuous protrusion e g. taking the form of a collar or flange.

Preferably, but not necessarily always, the support is positioned substantially towards an end of the casing that defines the outlet. When used as a heart pump, this arrangement reduces the length of the casing that extends into the aorta or pulmonary artery. This improves blood flow properties within the artery, especially flow to the coronary arteries, and also makes the pump easier to implant.

It is preferred that the support comprises apertures through which a fastener can be passed to retain the pump to the conduit wall. The protrusion may take the form of a solid body which may be formed as an integral part of the outer casing. Alternatively, the support may include of a woven fabric, e.g. a sewing ring arrangement as commonly used to fit replacement heart valves.

In one variation, where the pump is used as a heart pump, a lateral facing surface of the protruding support is arranged to sit against a downstream side of the aortic/pulmonary valve annulus to form a seal there between. A liquid tight seal may also be formed between a radially outward facing surface of a portion of the outer wall of casing adjacent and on the inlet side of the protrusion, and a radially inward facing surface of the aortic/pulmonary valve annulus. In this arrangement, the electrical lead may pass out through the outer casing adjacent and on the inlet side of the protrusion.

In an alternative variation, the protrusion is arranged to sit within the aperture of the aortic/pulmonary valve annulus so that a seal is formed between the radially outward facing surface of the, preferably projecting, support and the radially inward facing surface of the annulus

It is preferred that the driving mechanism is arranged to rotate the pump element to impel fluid through the conduit, the pump element being rotatably mounted within a path for fluid flow defined by the cavity.

The casing preferably carries the driving means so that the driving means can to be held within the conduit without coming into contact with the fluid flowing there through. Preferably the casing defines a fluid tight cavity in which the driving means, and further preferably a portion of the electrical lead, are housed.

The case may comprise a hollow inner housing that defines the fluid flow path and an outer housing. The driving mechanism is favourably housed between the inner and outer housings.

It may be preferred for the pump to include a one way valve to regulate flow of fluid through the pump. It is favourable that the one way valve is positioned towards the outlet of fluid flow. Preferably the axial separation between the support and the outlet end of the casing of less or equal to about two centimetres.

It is favourable that the casing resembles a straight tube arranged such that fluid flow through the inlet is substantially coaxial with fluid flow through the outlet. This allows the pump to be conveniently positioned within a straight portion of the conduit. In the case of a heart pump, it allows the pump to be located at the exit of either ventricle while minimising the likelihood of interference with the interventricular septum or other intraventricular structures like valves, chords etc.

It is preferred that the pump element comprises a magnet and the driving mechanism comprises a coiled elongate electrical conductor. In this way the pump element or impeller also functions as a rotor and the coil a stator, simplifying the design of the pump.

In a preferred embodiment, the pump is suitable for intravascular implantation within a human to pump blood. The support may be arranged for supporting the pump against an aortic annulus or pulmonary annulus; and the electrical lead arranged to pass through the support for passage through the aortic or pulmonary annulus.

The support is preferably adapted to allow a suture to be passed therethrough in order to retain the support, and thus the blood pump, against the aortic annulus or pulmonary annulus.

Preferably the electrical lead comprises an elongate electrically conducting element sheathed with an electrical insulator. The sheath preferably comprises a biocompatible material.

The invention will now be described by example with reference to the following figures in which:

Figure 1 is a view of a blood pump shown with the casing partly cut away to reveal the a rotor and a stator therein;

Figure 2illustrates the blood pump of Figure 1 ready for insertion into the pulmonary artery for mounting against the pulmonary valve annulus;

Figure 3 illustrates the blood pump mounted against the pulmonary valve annulus to draw blood from the right ventricle into the pulmonary artery;

Figure 4 is a side view of the blood pump as shown in Fig 3; and

Figure 5 illustrates a variant design of pump mounted against the pulmonary valve annulus to draw blood from the right ventricle into the pulmonary artery.

Referring to Figures 1-4 there is shown a blood pump 1 that forms part of a ventricular assist device.

In use, the blood pump 1 is arranged to sit at the exit of either ventricle V of a human heart extending through and anchored to the aortic valve annulus or pulmonary valve annulus A; the valve cusps having been excised.

The pump 1 comprises a casing having an inner housing2 and an outer housing 3. The inner and outer housings 2, 3 are spaced apart to define betwixt a, typically annular, cavity 4. An inward extending flange 3A provided by the outer housing 3 and a cap 5 close the opposing ends of the cavity 4 so that the cavity 4 is sealed from ingress of blood.

The inner housing 2 is hollow to define a straight pathway for blood flow through the pump 1. A first end of the housing defines an inlet lAof the pathway and a second end defines an outlet IB of the pathway. The inlet 1A and outlet IB are arranged to provide a substantially coaxial inflow and outflow of blood represented by dashed arrowed line X.

As shown in Fig 1, within the pathway, between the inlet 1A and outlet IB, is housed an auger type impeller 6 having helical flights 6A. The impeller 6 is supported by bearings (not shown) at either end for rotation within the pathway to move blood along the impeller’s 6 axis of rotation towards the outlet IB. Mounted within the flights 6A, towards the outlet end of the impeller 6, are permanent magnets 7.

Mounted within the annular cavity 4, for isolation from blood within or outside of the pump 1 is a driving means comprising a coil winding 8 and laminated core 8A.The coil winding and laminated core 8 8A surround the portion of the impeller 6 that houses the magnets 7.

With this arrangement, the impeller 6 may act akin to a rotor of an electrical motor with the laminated core 8A with coil 8 akin to a stator. Rotation of the impeller 6 is effected by control of an electrical current through the coil 8. More details of this arrangement together with the additionally preferred features of a flow straightener 9A and a diffuser 9B (see Fig 2) are described in more detail within US patent 5,692,882 and so will not be detailed further.

The outer housing 3 comprises a circumferential collar 3B that extends radially away from the axis of blood flow X through the pump 1.

It is preferred that the outer housing 3 including collar 3B formed from a single integral piece, e.g. of titanium or other bio-compatible material, defining pairs of apertures 3C that extend between lateral sides of the collar 3B that are circumferentially spaced around the collar 3B.

Figures 1-4 illustrate the collar 3B positioned towards the axial centre of the pump 1 in order to suit patients suffering from forms of restrictive cardiomyopathy like hypertrophic cardiomyopathy and other forms of infiltrative cardiomyopathy where the intraventricular cavity size is relatively small, where it is desirous to reduce the extent that the pump protrudes into the ventricular cavity to, preferably, no more than three centimetres. Nevertheless, for most other patients, it is preferred that the collar 3B is positioned towards the outlet of the pump 1, with an axial separation of about two centimetres or less, and possibly none at all, in order to ease implantation onto the annulus, and when mounted in the aorta, to ensure antegrade flow into the coronary arteries.

The ends of the coil 8 are connected to sheathed elongate electrical conductors 10 that extend through the cavity 4, passing radially through the collar 3B and out through a radially outward facing surface 3Dof the outer casing 3 adjacent to and on an inlet side of the collar 3B. A portion 10A of the electrical conductors 10 that extend beyond the surface 3D are long enough to pass through the annulus A into the body cavity for connection to a power supply (not shown) to provide current to the coil 8.

To implant the pump 1 as part of aright ventricular assist device, a lateral incision is made in the pulmonary artery P (see Figure 4) above the pulmonary valve. Preferably the incision does not completely sever/ transect the artery. The pulmonary valve may be removed in a manner identical to that used in valve replacement surgery to leave the pulmonary valve annulus A. A series, e g. twenty though it may be more or less, sutures S are passed at various circumferentially spaced points around the pulmonary valve annulus A to extend through upstream A1 and downstream A2 facing surfaces of the pulmonary valve annulus A.

If not already posited, the portions of suture S extending from the downstream side A1 of the annulus A are passed through one of each pair of apertures 3C that corresponds with circumferential position of the suture relative the annulus. The ends of the sutures that extends beyond the upstream facing surface are either passed back through the annulus and up through the other aperture 3C of the pair that the other end of the suture S extends through.

The portions of elongate conductors 10A are fed via the lateral incision into the pulmonary artery P and through a radial hole formed within the pulmonary valve annulus A so that the free ends of the electrical connectors 10A sit outside of the pulmonary artery P.

The pump 1 is also passed through the lateral incision into the pulmonary artery P until the collar 3B is seated on the downstream face A2 of the pulmonary valve annulus A. During this process the free ends of the sutures S may be pulled through the collar 3B.

Once seated, the ends of sutures are tied to hold the downstream face of the annulus against the inlet facing surface of the collar 3B and draw to hold the radially inward facing surface of annulus A against, to form a liquid tight interface with, radially outward facing surface 3D of outer casing 3.

The electrical connectors 10A are connected to a remote power source/controller which for example, may be positioned subcutaneously, adjacent a pectoral muscle as is known in the art. Once implanted, the pump 1 is supported about and sits within the aperture of the pulmonary valve annulus A, extends into the ventricle V, to draw blood from within the ventricle and convey it through the pulmonary valve annulus into the pulmonary artery. A substantially identical procedure may be used to implant the pump 1 to assist the left ventricle that involves partly severing the aorta, removing the flaps of the aortic valve, and anchoring the pump 1 to the aortic valve annulus A with the electrical connectors 10A passing through said aortic valve annulus A. A pump Γ of a variant design is illustrated in Fig 5 in which the electrical conductors 10A’ pass out of the casing 3’ through the radially outwardly face 3E’of the collar 3B\ Further, the collar 3B’ has circumferentially spaced apertures 3C’ rather than pairs thereof.

The pump Γ is implanted such that the collar 3B’ sits within the aperture of the annulus A with the radially inward facing surface of annulus facing, and when the sutures S are tied, abutting to seal against the radially outward face 3E’ of the collar 3B’. During implantation, the sutures S are passed through the annulus as before and the free end extending from the upstream face of the annulus A brought through the central aperture of the annulus A and aperture 3C’ corresponding to the circumferential position within the collar 3B\ Once the pump 1’ is in position, the free ends of the suture S are tied to draw the annulus A against radially outward face 3E’ to form a liquid tight seal.

The collar 3B, 3B’ may take other forms, for example it may be formed by a number of discrete radial protrusions that are circumferentially spaced.

The pump 1 may further include a one way valve, preferably positioned towards the outlet of the pump 1 to further regulate flow of fluid through the pump 1.

It is possible for the pump 1 to have a different shaped housing and have different mechanism and impeller forms.

Typically the pump is of a straight tubular form with a circular cross section though variations of this shape are possible.

In alternative embodiments the collar 3B may comprise may be formed or comprise a fabric or other penetrable material to resemble a conventional sewing ring used with replacement heart valves and the like.

Sutures are a common and accepted means of fastening implantable devices into the body. However, where the pump is used for purposes other than implantation into the body, it may be arranged to be fastened to the inner wall of the conduit by other fasteners that are well known in the art.

Claims

1. A pump adapted for operation within a fluid carrying conduit to compel fluid through the conduit, the pump having: a casing defining an inlet and an outlet, the casing housing a pump element and a driving mechanism to drive the pump element to compel fluid through the conduit; a support for supporting the pump to a wall of the conduit; and further comprising an electrical lead that passes out of the casing either through the support or through an outer wall of the casing at an inlet side of the support, for passage through the conduit wall to a power source to supply power to the drive mechanism.

2. A pump according to claim 1 wherein the electrical lead passes through the support for passage through the conduit wall to a power source to supply power to the drive mechanism.

3. A pump according to claim 1 wherein the electrical lead passes out through an outer wall of the casing at an inlet side of the support, for passage through the conduit wall to a power source to supply power to the drive mechanism.

4. A pump according to claim 2 or 3 wherein the support defines a supporting surface, which when the pump is operated within the conduit, sits against an inner surface of the conduit wall; the electrical lead passing through the supporting surface.

5. A pump according to any previous claim comprising a substantially continuous circumferential supporting surface to provide, when the pump is mounted within the conduit, a substantially continuous circumferential liquid tight interface with the inner surface of the conduit wall.

6. A pump according to any previous claim wherein the support is positioned substantially towards an end of the casing that defines the outlet.

7. A pump according to any previous claim wherein the support comprises apertures through which a fastener can be passed to retain the pump to the conduit wall.

8. A pump according to any previous claim wherein the support comprises a protrusion that extends laterally away from the direction of fluid flow through the conduit.

9. A pump according to claim 8 wherein the protrusion is substantially circumferentially continuous.

10. A pump according to any previous claim wherein the driving mechanism is arranged to rotate the pump element to compel fluid through the conduit.

11. A pump according to claim 10 wherein the casing defines a path for fluid flow through the pump, the pump element is rotatably mounted within the path for fluid flow and the driving means is outside of path for fluid flow, isolated from the fluid within the conduit.

12. A pump according to claim 11 wherein the case comprises an inner housing that defines the fluid flow path, and an outer housing, and wherein the driving mechanism is housed between the inner and outer housings.

13. A pump according to claiml2 wherein the protrusion is formed as an integral part of the outer casing.

14. A pump according to any claim 10 to 13 wherein the pump element comprises a magnet and the driving mechanism comprises a coiled elongate electrical conductor.

15. A pump according to any previous claim comprising a one way valve to regulate flow of fluid through the pump.

16. A pump according to claim 15 wherein the one way valve is positioned towards the outlet of the casing.

17. A pump according to any previous claim wherein the axial separation between the support and the outlet end of the casing is less or equal to about two centimetres.

18. A pump according to any previous claim wherein the casing defines a substantially straight fluid flow path between the inlet and the outlet and in which the inlet and outlet are arranged such that fluid flow through the inlet is substantially aligned with fluid flow through the outlet.

19. A pump according to any previous claim that is suitable for intravascular implantation to pump blood,

20. A pump according to claim 19 wherein the support is arranged for supporting the pump against an aortic annulus or pulmonary annulus; and the electrical lead arranged to pass through or adjacent the support for passage through the aortic or pulmonary annulus.

21. A pump according to claim 18 or 19 wherein the support is adapted to allow a suture to be passed therethrough in order to retain the support against the aortic annulus or pulmonary annulus.

22. A method of implanting a heart pump comprising: providing a blood pump having a casing housing a pump element and defining a pathway for blood flow between an inlet to the pump and outlet of the pump; and implanting the blood pump intravascularly, proximate a heart, so as to have an inlet lying within either a ventricle of the heart to compel blood flow out of the heart; the pump being implanted such that it either: extends through an aperture of the aortic annulus so as to have an inlet within a left ventricle and an outlet into an aorta; or extends through an aperture of the pulmonary annulus to have the inlet in a right ventricle and the outlet in a pulmonary artery.

23. A method according to claim 22wherein an electrical lead of the pump that extends away from the casing to provide an electrical connection to a power supply located remote from the pump, is passed through the aortic or pulmonary annulus and out of the intravascular system.

24. A method according to claim 22 wherein the lead is passed through the annulus before the pump is seated in the annulus aperture.

25. A method according to claim 21, 22 or 23 wherein cusps supported by the annulus are excised before the pump is seated.

26. A method according to any claim 21-24 of implanting a heart pump into a human body.

27. A method according to any claim 22-26 of implanting a heart pump into a non-human mammalian body.

28. A blood pump suitable for intravascular implantation so as to have an inlet lying within either the left ventricle or right ventricle of the heart, to compel blood flow, when implanted with inlet in said left ventricle, through an aperture of the aortic annulus into the aorta, or when implanted to have inlet in said right ventricle, through an aperture of the pulmonary annulus into pulmonary artery.

29. An intravascularly implanted heart pump mounted to and extending through either: an aperture of the aortic annulus so as to have an inlet within a left ventricle and an outlet into an aorta to pump blood from the left ventricle through the aperture of the aortic annulus into the aorta, or an aperture of the pulmonary valve annulus to have the inlet in a right ventricle and the outlet in a pulmonary artery to pump blood from the right ventricle through the aperture of the pulmonary valve annulus into the pulmonary artery; and wherein the heart pump comprising an electrical lead that extends through: when mounted to and extending through an aperture of the aortic annulus, the aortic annulus; or when mounted to and extending through an aperture of the pulmonary valve annulus, the pulmonary valve annulus.

30. A pump adapted for operation within a fluid carrying conduit to compel fluid through the conduit, the pump having: a casing defining an inlet and a outlet, the casing housing a pump element and a driving mechanism to drive the pump element to compel fluid through the conduit; a support for supporting the pump to a wall of the conduit; and further comprising an electrical lead that passes through the support, for passage through the conduit wall to a power source to supply power to the drive mechanism.