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Title:
PULSATILE BLOOD PUMP
Document Type and Number:
WIPO Patent Application WO/2011/117566
Kind Code:
A1
Abstract:
There is described a pulsatile blood pump for implantation into a patient. The blood pump comprises a flexible, substantially tubular body for disposal coaxially within a blood vessel of the patient. The tubular body has first and second ends with a blood passageway extending therebetween for the passage of blood, and the tubular body has a collapsed state for use during delivery and an expanded state for use during pumping. The blood pump further comprises deformable elements coupled to the tubular body and arranged to retain the tubular body in the expanded state following delivery. The blood pump further comprises a flexible membrane attached to the tubular body so as to form a fluid chamber within the tubular body. The flexible membrane separates the fluid chamber from the blood passageway. In the expanded state of the tubular body, the blood pump is arranged such that fluid is able to flow into and out of the fluid chamber whereby the volume of the fluid chamber increases and the volume of the blood passageway decreases when fluid flows into the fluid chamber, and whereby the volume of the fluid chamber decreases and the volume of the blood passageway increases when fluid flows out of the fluid chamber, thereby enabling the blood pump to pump blood along the blood passageway. There is also described a blood pump system comprising the present blood pump, a method for the treatment of heart failure in a patient using the present blood pump, and a method for augmenting peripheral blood circulation in a patient using the present blood pump.

Inventors:
TANSLEY, Geoffrey, Douglas (2 Langley Drive, Kegworth, Derbyshire DE74 2DN, GB)
RICHENS, David (145 Musters Road, West BridgfordNottingham, Nottinghamshire NG2 7AF, GB)
Application Number:
GB2011/000354
Publication Date:
September 29, 2011
Filing Date:
March 11, 2011
Export Citation:
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Assignee:
ASTON UNIVERSITY (Business Partnership Unit, Aston Triangle, Birmingham B4 7ET, GB)
NOTTINGHAM UNIVERSITY HOSPITALS NHS TRUST (City Hospital Campus, Hucknall RoadNottingham, Nottinghamshire NG5 1PB, GB)
TANSLEY, Geoffrey, Douglas (2 Langley Drive, Kegworth, Derbyshire DE74 2DN, GB)
RICHENS, David (145 Musters Road, West BridgfordNottingham, Nottinghamshire NG2 7AF, GB)
International Classes:
A61M1/10
Domestic Patent References:
2000-06-22
2009-04-02
2009-04-02
Foreign References:
EP2016961A12009-01-21
US6210318B12001-04-03
EP0192574A11986-08-27
EP1318848A12003-06-18
EP1560614A12005-08-10
US4733652A1988-03-29
US6030355A2000-02-29
US4195623A1980-04-01
US4015590A1977-04-05
Attorney, Agent or Firm:
MCLEISH, Nicholas Alistair Maxwell (BOULT WADE TENNANT, Verulam Gardens70 Gray's Inn Road, London WC1X 8BT, GB)
Download PDF:
Claims:
CLAIMS:

1. A pulsatile blood pump for implantation into a patient, the blood pump comprising:

a flexible, substantially tubular body for disposal coaxially within a blood vessel of the patient, wherein the tubular body has first and second ends with a blood passageway extending therebetween for the passage of blood, and wherein the tubular body has a collapsed state for use during delivery and an expanded state for use during pumping;

deformable elements coupled to the tubular body and arranged to retain the tubular body in the expanded state following delivery; and

a flexible membrane attached to the tubular body so as to form a fluid chamber within the tubular body, the flexible membrane separating the fluid chamber from the blood passageway;

wherein, in the expanded state of the tubular body, the blood pump is arranged such that fluid is able to flow into and out of the fluid chamber whereby the volume of the fluid chamber increases and the volume of the blood passageway decreases when fluid flows into the fluid chamber, and whereby the volume of the fluid chamber decreases and the volume of the blood passageway increases when fluid flows out of the fluid chamber, thereby enabling the blood pump to pump blood along the blood passageway.

2. The blood pump of claim 1 wherein the flexible membrane is attached to the tubular body so as to form the fluid chamber between the flexible membrane and an inner surface of the tubular body.

3. The blood pump of claim 2 wherein the flexible membrane is formed as a sheet and is attached across a chord of the tubular body such that the fluid chamber and the blood passageway are disposed side by side within the tubular body.

420268

4. The blood pump of claim 2 wherein the flexible membrane is formed as a tube and is attached at or near each end of the tubular body such that the blood passageway is disposed concentrically within the fluid chamber. 5 The blood pump of claim 1 wherein the flexible membrane is attached to the tubular body such that the formed fluid chamber is entirely bounded by the flexible membrane.

6. The blood pump of any preceding claim further comprising one or more baffles in the fluid chamber to channel fluid in a direction from the first end towards the second end as it enters the fluid chamber, thereby enabling the blood pump to preferentially pump blood along the blood passageway from the first end towards the second end. 7. The blood pump of claim 6 wherein the baffles comprise a spiral configuration.

8. The blood pump of any preceding claim wherein the flexible membrane has elastic properties.

9. The blood pump of any preceding claim further comprising a check valve arranged to allow fluid to flow through the blood passageway in one direction only. 10. The blood pump of any preceding claim wherein the tubular body comprises one or more non-stretch elements for preventing the tubular body from distending significantly from its expanded state when fluid flows into the fluid chamber. 1 1. The blood pump of claim 10 wherein the non-stretch elements are non- stretch filaments having an axial configuration with respect to the tubular body.

420268

12. The blood pump of any preceding claim wherein the tubular body and the deformable elements together form a stent graft.

13. The blood pump of any preceding claim wherein the deformable elements comprise a superelastic shape memory alloy.

14. The blood pump of any of claims 1 to 13 wherein the deformable elements are coupled to an external surface of the tubular body. 15. The blood pump of any of claims 1 to 13 wherein the deformable elements are coupled to an internal surface of the tubular body.

16. The blood pump of any preceding claim wherein the deformable elements comprise wires formed into one of a cylindrical diamond mesh coaxial with the tubular body and a cylindrical zig-zag configuration coaxial with the tubular body.

17. The blood pump of any preceding claim wherein a wall of the tubular body is puncturable from outside to enable insertion of one end of a fluid conduit into the fluid chamber such that the fluid chamber is in fluid communication with the fluid conduit.

18. The blood pump of any preceding claim wherein the blood pump is deliverable by catheter when the tubular body is in its collapsed state. 19. The blood pump of any preceding claim further comprising a securing device arranged to secure the blood pump within the blood vessel of the patient.

20. A blood pump system comprising:

a blood pump according to any preceding claim;

a fluid conduit connected to the tubular body of the blood pump to allow fluid to flow into and out of the fluid chamber; and

420268 a drive unit coupled to the fluid conduit and operable to drive fluid alternately into and out of the fluid chamber via the fluid conduit.

21 . The blood pump system of claim 20 further comprising a pressure sensor operable to measure pressure in the fluid conduit, wherein the drive unit is responsive to the measured pressure.

22. The blood pump system of claim 20 or claim 21 further comprising a pressure sensor operable to measure pressure in the fluid chamber, wherein the drive unit is responsive to the measured pressure.

23. The blood pump system of any of claims 20 to 22 further comprising an electrocardiograph, wherein the drive unit is responsive to electrocardiographic data.

24. The blood pump system of any of claims 20 to 23 wherein the drive unit is operable to drive the blood pump in counter-pulsation with the patient's heart.

25. The blood pump system of any of claims 20 to 24 wherein a first end of the fluid conduit is connected to the tubular body of the blood pump, and a second end of the fluid conduit comprises a connector, wherein the connector is self- sealing.

26. A method for the treatment of heart failure in a patient, the method comprising:

providing a blood pump according to any one of claims 1 to 19;

using a catheter to deliver the blood pump to a blood vessel of the patient, the tubular body of the blood pump being in its collapsed state during delivery; expanding the tubular body into its expanded state following delivery of the blood pump to the blood vessel;

420268 inserting a first end of a fluid conduit through walls of both the blood vessel and the tubular body to allow fluid to flow into and out of the fluid chamber via the fluid conduit; and

driving fluid along the fluid conduit alternately into and out of the fluid chamber of the blood pump, thereby enabling the blood pump to pump blood along the blood passageway.

27. The method of claim 26 wherein the fluid conduit is a percutaneous drive line with a second end extending out of the patient.

28. The method of claim 26 or 27 wherein the blood vessel is the ascending aorta.

29. The method of any of claims 26 to 28 further comprising measuring a pressure within the fluid conduit, the driving of fluid along the fluid conduit being responsive to the measured pressure.

30. The method of any of claims 26 to 29 further comprising measuring a pressure within the fluid chamber, the driving of fluid along the fluid conduit being responsive to the measured pressure.

31. The method of any of claims 26 to 30 further comprising measuring electrocardigraphic data of the patient, the driving of fluid along the fluid conduit being responsive to the measured electrocardigraphic data.

32. The method of any of claims 26 to 31 wherein the blood pump is driven in counter-pulsation with the patient's heart.

33. The method of any of claims 26 to 32 further comprising correcting the underlying cardiac defect leading to the patient's heart failure.

420268

34. The method of any of claims 26 to 33 further comprising one of partial thoracotomy, thoracotomy, partial sternotomy, sternotomy, minimally invasive surgical approaches and arterial access to enable the delivery of the blood pump to the blood vessel.

35. The method of any of claims 26 to 34 wherein the outer diameter of the tubular body matches the inner diameter of the blood vessel.

36. A method for augmenting peripheral blood circulation in a patient, the method comprising:

providing a blood pump according to any one of claims 1 to 19;

using a catheter to deliver the blood pump to a peripheral blood vessel of the patient, the tubular body of the blood pump being in its collapsed state during delivery;

expanding the tubular body into its expanded state following delivery of the blood pump in the blood vessel;

inserting a first end of a fluid conduit through walls of both the blood vessel and the tubular body to allow fluid to flow into and out of the fluid chamber via the fluid conduit; and

driving fluid along the fluid conduit alternately into and out of the fluid chamber of the blood pump, thereby enabling the blood pump to pump blood along the blood passageway.

420268

Description:
PULSATILE BLOOD PUMP

FIELD OF THE INVENTION

The present invention relates to a pulsatile blood pump for implantation into a patient. The invention also relates to a blood pump system incorporating such a pulsatile blood pump, and to a method for the treatment of heart failure in a patient.

BACKGROUND OF THE INVENTION

Heart failure is a major cause of death in the developed and developing world; it is estimated that there are currently 901 ,500 sufferers in the United Kingdom with 65,000 new cases added annually. The British Heart Foundation estimates the annual cost of heart failure is £625 million in the UK alone. In the United States, the corresponding statistics are 5,000,000 sufferers with 550,000 new cases annually and an annual cost to the US economy of $296,000 million. The World Health Organisation estimates that cardiovascular disease (CVD), around 7% of which is heart failure, contributed to 1/3 of all deaths worldwide and will be the major cause of death by 2010.

The prognosis for heart failure sufferers is poor, with just less than 40% dying within the first year. Furthermore, 5% of all deaths in the UK,

approximately 24,000 per annum, are attributable to heart failure. Around 40% of these patients suffer from impaired left ventricular systolic function and could benefit from mechanical support e.g. with a Left Ventricular Assist Device

(LVAD). The best therapy for many of these patients would be heart

transplantation; however the demand for donor hearts in the USA alone is around 100,000 per annum and far exceeds the 2,200 donor hearts available per annum; this pattern is similar the world over. The other main therapies commonly available are medical, such as inotropes, ACE inhibitors, Beta blockers, diuretics and nitrates, or are mechanical support therapies, such as the use of a Total Artificial Hearts (TAHs) or Ventricular Assist Devices.

There is a continuum of treatment modalities for patients suffering chronic heart failure. As the disease progresses patients will receive increasingly

420268 aggressive medical therapies, but most patients become refractory to medical therapies at some point and their health will decline. Patients eligible for cardiac transplantation would typically receive medical therapies whilst awaiting transplantation; if their condition deteriorated then mechanical "bridge to transplantation", may be adopted in the form of a mechanical support device such as an Intra-Aortic Balloon Pump (IABP), Extra-Aortic Balloon Pump (EABP), or other LVAD dependent on the duration of the bridging. Patients who are supported in bridge to transplantation whilst awaiting transplantation are in a better state of health at the time of transplantation, are more likely to survive transplant surgery and have a better long-term prognosis. Patients ineligible for transplantation typically follow a medical therapy-only path, though with the most aggressive health-care providers may receive mechanical support, e.g. a LVAD or a TAH in "destination therapy".

Several mechanical devices are currently available, or are in development, which support cardiac function in heart failure. Rotary Blood Pumps (RBPs) take blood typically from the ventricle of the native heart, energise it through the action of a rotating impeller, and deliver the blood to the ascending aorta. These devices allow the patient to ambulate, but do not produce pulsatile blood flow as does the native heart. In contrast, RBPs typically act at a constant rotational speed, can be difficult to control, and are expensive in their implanted form.

lABPs, such as those described in US6210318 and EP0192574, are well established technology and comprise small balloons which are inserted into the aorta and which are inflated and deflated, typically in anti-phase with the native heart, through the action of pneumatic fluid acting behind a flexible polymeric membrane. EABPs, such as those described in EP1318848, EP1560614, and US4733652, are attached to the external surface of the aorta rather than being implanted within the aorta. Disadvantages of EABPs can include atheromous emboli through interaction with the aortic wall, and migration and interference with neighbouring structures, e.g. erosion of the pulmonary artery or lungs. Other technologies which similarly augment blood flow using balloon pumps include: a balloon pump for insertion into the descending aorta described in US6030355, but this device has a rigid outer body which precludes its implantation at the

420268 optimal position in the lower ascending aorta where pumping effect is optimised; and the conduit mounted balloon pumps described in US4195623 and

US4015590 which similarly are non-optimally positioned.

The present invention extends the inventors' work on the "Chronic

Intermittent Mechanical Support" (CI MS) for the treatment of heart failure. The CIMS system is described in WO2009/040560.

The present invention seeks to provide an alternative pump which provides various advantages over those of the prior art when used in cardiac support.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a pulsatile blood pump for implantation into a patient. In this context, the term "pulsatile blood pump" means a pulsatile pump suitable for pumping blood.

Although the pulsatile blood pump of the first aspect of the present invention is suitable for pumping blood, it could also be used to pump other fluids if desired. The pulsatile blood pump comprises a flexible, substantially tubular body, deformable elements, and a flexible membrane. The flexible, substantially tubular body is for disposal coaxially within a blood vessel of the patient. The "substantially" wording means that the cross section of the tubular body need not be exactly circular. For example, an oval cross-section might be considered to be "substantially" circular. In addition, the cross section of the substantially tubular member may change in shape and/or size axially along its length so as to best match the portion of blood vessel into which it is placed or so as to afford other benefits whilst in use. The tubular body has first and second ends with a blood passageway extending therebetween for the passage of blood. The tubular body has a collapsed state for use during delivery and an expanded state for use during pumping. The deformable elements are coupled to the tubular body and are arranged to retain the tubular body in the expanded state following delivery of the blood pump to the desired blood vessel. The flexible membrane is attached to the tubular body so as to form a fluid chamber within the tubular body. The flexible membrane separates the fluid chamber from the blood

420268 - 4 - passageway. In the expanded state of the tubular body, the blood pump is arranged such that fluid is able to flow into and out of the fluid chamber whereby the volume of the fluid chamber increases and the volume of the blood

passageway decreases when fluid flows into the fluid chamber, and whereby the volume of the fluid chamber decreases and the volume of the blood passageway increases when fluid flows out of the fluid chamber, thereby enabling the blood pump to pump blood along the blood passageway

The tubular body is connectable to a fluid conduit to allow fluid to flow into and out of the fluid chamber.

Thus, the outflow from the native heart may be augmented through the use of the blood pump of the present invention. The blood pump is surgically placed coaxially within the aorta or other blood vessel by minimally invasive surgery and delivered by a catheter device. This is facilitated by the substantially circular section of the blood pump being collapsible so that it can be catheter fed to the site of installation and then expanded so as to make intimate contact with the inner lumen of the blood vessel. Once expanded, the shape and dimension of the substantially tubular body of the blood pump remains expanded through the use of super-elastically deformable elements or other elements which hold the tubular body open in a way similar to that in which a stent graft is held open. The cross-sectional area of the blood passageway through the blood pump is caused to contract due to the flow of fluid into and out of the fluid chamber between the tubular body and the flexible membrane of the blood pump. The blood pump may be used in the temporary or long-term treatment of patients suffering heart failure through intermittent or temporary continuous use when counter-pulsed with the natural heart. Additional embodiments can also be contemplated so as to reduce the workload required from the native heart, to augment coronary artery perfusion, and/or to treat other circulatory diseases by introducing such a blood pump into the peripheral circulation. Patients who would most benefit from use of the blood pump of the present invention may be divided into groups, as described below.

420268 The first group of patients who would derive a significant benefit are patients needing temporary support or bridge to recovery treatment. This group of patients is refractory to medical therapies and will present with declining cardiac and end-organ function, but when supported with a mechanical device will recover cardiac function, typically within around twenty weeks of mechanical support, such that support may then be withdrawn. However, current mechanical LVADs do not incorporate one-way valves making it infeasible to leave them in- situ and deactivated due to significant retrograde flow through them once they have been inactivated. Current LVADs therefore do not provide a life-line to recovered patients, and re-operation is necessary to implant an additional device if cardiac function declines once again. In contrast, the present invention will allow support to be withdrawn on recovery, but for the blood pump to remain in place should intermittent support be required thereafter; it is also feasible to withdraw the blood pump by collapsing it back to the size and state it was in during delivery and withdrawing it should this be considered a better option for the patient.

The second group of patients for whom the present invention would be particularly beneficial are patients needing long term chronic support. This group of patients will never recover cardiac function and will be maintained on medical therapies in the long term. The "healthier" of these are minimally supported with medical therapies but require more aggressive support intermittently;

typically such patients would be admitted to hospital for one or two weeks respite and receive low doses of inotropes and diuretics which is sufficient to reduce ventricular overload, to restore end organ function and to promote a feeling of well being. Patients receiving more aggressive medical therapies need additional support in times of crisis and would be admitted to intensive care and aided with an IABP such as those of US62103188 and EP0192574. Patients with the worst therapies in the long term. I he ' heaitnie ' r ΰτ ine " s " e are miilirirdiiy A 5opy i t¾cr¾hoT medical therapies but require more aggressive support intermittently;

typically such patients would be admitted to hospital for one or two weeks respite and receive low doses of inotropes and diuretics which is sufficient to reduce ventricular overload, to restore end organ function and to promote a feeling of well being. Patients receiving more aggressive medical therapies need additional support in times of crisis and would be admitted to intensive care and aided with an IABP such as those of US62103188 and EP0192574. Patients with the worst present invention, in addition to medical therapy to provide respite. Once installed, and for subsequent readmission, use of the present blood pump can be very quickly effected and will be fast acting. For patients on higher doses of medication in crisis, the present invention will allow speedier deployment and will allow the patient to be ambulatory and reduce the risk of infection posed by lABPs, as described further below. The present invention will greatly reduce the cost of bridge-to-transplantation by removing the need for an implanted VAD or the need for intensive care beds that would have been required if an external VAD were used.

In one embodiment of the present invention, the flexible membrane is attached to the tubular body so as to form the fluid chamber between the flexible membrane and an inner surface of the tubular body. For example, the flexible membrane may be formed as a sheet and may be attached across a chord of the tubular body such that the fluid chamber and the blood passageway are disposed side by side within the tubular body. Alternatively, the flexible membrane may be formed as a tube and may be attached at or near each end of the tubular body such that the blood passageway is disposed concentrically within the fluid chamber.

In an alternative embodiment, the flexible membrane is attached to the tubular body such that the formed fluid chamber is entirely bounded by the flexible membrane. This embodiment provides the advantage that the tubular body need not be formed from a material which is impermeable to the pneumatic or hydraulic fluid which is to be pumped in and out of the fluid chamber. This allows a wider selection of material to be used.

As noted above, the flexible membrane is attached to the tubular body. Optionally, the flexible membrane may be attached to the inner surface of the tubular body. It may be attached in a parallel or doubled-back configuration. Alternatively/additionally, the flexible membrane may be attached to the ends of the tubular body.

Advantageously, the blood pump may further comprise one or more baffles in the fluid chamber to channel fluid in a direction from the first end

420268 W

- 7 - towards the second end as it enters the fluid chamber, thereby enabling the blood pump to preferentially pump blood along the blood passageway from the first end towards the second end. In one embodiment, the baffles may comprise a spiral configuration.

Advantageously, the flexible membrane may have elastic properties.

Advantageously, the blood pump may further comprise a check valve arranged to allow fluid to flow through the blood passageway in one direction only.

In one embodiment, the tubular body may comprise one or more non- stretch elements for preventing the tubular body from distending significantly when fluid flows into the fluid chamber. For example, the non-stretch elements may be non-stretch filaments having an axial configuration with respect to the tubular body.

Advantageously, the tubular body may have a smooth outer profile.

Advantageously, the tubular body and the deformable elements may together form a stent graft.

Advantageously, the deformable elements may comprise a superelastic shape memory alloy.

In one advantageous embodiment, the deformable elements may be coupled to an external surface of the tubular body. In an alternative embodiment, the deformable elements may be coupled to an internal surface of the tubular body.

In one embodiment, the deformable elements may comprise wires formed into a substantially tubular structure coaxial with the tubular body. The wires may be in the form of a diamond mesh or may form rings of zig-zags.

Advantageously, a wall of the tubular body may be puncturable from outside to enable insertion of one end of a fluid conduit into the fluid chamber such that the fluid chamber is in fluid communication with the fluid conduit.

Alternatively, a wall of the tubular body may comprise a pre-fabricated aperture for insertion of one end of a fluid conduit into the fluid chamber. To facilitate deployment of the blood pump, the fluid conduit which carries fluid to inflate the

420268 fluid chamber can be connected to the tubular body of the blood pump following deployment of the blood pump.

Advantageously, the blood pump may be deliverable by catheter when the tubular body is in its collapsed state.

Advantageously, the blood pump may further comprise a securing device arranged to secure the blood pump within the blood vessel of the patient.

According to a second aspect of the present invention, there is provided a blood pump system comprising: a blood pump in accordance with the first aspect of the present invention, a fluid conduit connected to the tubular body of the blood pump to allow fluid to flow into and out of the fluid chamber, and a drive unit coupled to the fluid conduit and operable to drive fluid alternately into and out of the fluid chamber via the fluid conduit.

In one embodiment, the blood pump system may further comprise a pressure sensor operable to measure pressure in the fluid conduit, and the drive unit may be responsive to the measured pressure. Alternatively/additionally, the blood pump system may further comprise a pressure sensor operable to measure pressure in the fluid chamber, and the drive unit may be responsive to the measured pressure.

Optionally, the blood pump system may further comprise an

electrocardiograph, and the drive unit may be responsive to electrocardiographic data.

Advantageously, the drive unit may be operable to drive the blood pump in counter-pulsation with the patient's heart.

Advantageously, a porous biocompatible material may be attached to an outer surface of a portion of the fluid conduit.

In one embodiment, the drive unit may be portable and wearable by a patient.

In one embodiment, a first end of the fluid conduit is connected to the tubular body of the blood pump, and a second end of the fluid conduit comprises a connector. The connector is self-sealing. Thus, if the connector is disposed just under the patient's skin, the connector will self seal on removal of the

420268 percutaneous section of fluid conduit. This is useful if the blood pump is disconnected and not in use for a significant period of time.

According to a third aspect of the present invention, there is provided a method for the treatment of heart failure in a patient. The method comprises: providing a blood pump of the first aspect of the present invention; using a catheter to deliver the blood pump to a blood vessel of the patient, the tubular body of the blood pump being in its collapsed state during delivery; expanding the tubular body into its expanded state following delivery of the blood pump to the blood vessel; inserting a first end of a fluid conduit through the blood vessel and the tubular body to allow fluid to flow into and out of the fluid chamber via the fluid conduit; and driving fluid along the fluid conduit alternately into and out of the fluid chamber of the blood pump, thereby enabling the blood pump to pump blood along the blood passageway.

Thus, the blood pump can be thought of as a stent graft which houses an inflatable-deflatable membrane. The blood pump is initially collapsed to a suitably small size to enable it to pass through a blood vessel or small incision for catheter delivery to the treatment site. Once at the treatment site, the catheter may be removed and the blood pump may be expanded in situ.

Advantageously, the fluid conduit may be a percutaneous drive line with a second end extending out of the patient.

In one embodiment, the blood vessel may be the ascending aorXa. In this case, access to the treatment site may be via an incision in the apex of the left ventricle or left atrium following a partial thoracotomy or stenotomy, or may be via an entry site in a major blood vessel such as the femoral artery or subclavian artery. The fluid conduit (i.e. the percutaneous drive line) is connected to the blood pump via a different access route.

Advantageously, the method may further comprise measuring a pressure within the fluid conduit, and the driving of fluid along the fluid conduit may be responsive to the measured pressure. Advantageously, the method may further comprise measuring a pressure within the fluid chamber, and the driving of fluid along the fluid conduit may be responsive to the measured pressure.

420268 Advantageously, the method may further comprise measuring

electrocardiographic data of the patient, and the driving of fluid along the fluid conduit may be responsive to the measured electrocardiographic data. The driving of fluid along the fluid conduit may also be responsive to both pressure and electrocardiographic measurements.

Advantageously, the blood pump may be driven in counter-pulsation with the patient's heart.

In one embodiment, the method may further comprise correcting the underlying cardiac defect leading to the patient's heart failure.

In one embodiment, the method may further comprise one of partial thoracotomy, thoracotomy, partial sternotomy, sternotomy, and arterial access to enable the delivery of the blood pump to the blood vessel. Any of a range of minimally invasive access and catheter-delivery methods may also be used to enable the delivery of the blood pump to the blood vessel.

Advantageously, the outer diameter of the tubular body may match the inner diameter of the blood vessel.

According to a fourth aspect of the present invention, there is provided a method for augmenting the peripheral blood circulation in a patient. The method comprises: providing a blood pump of the first aspect of the present invention; using a catheter to deliver the blood pump to a peripheral blood vessel of the patient, the tubular body of the blood pump being in its collapsed state during delivery; expanding the tubular body into its expanded state following delivery of the blood pump in the blood vessel; inserting a first end of a fluid conduit through the blood vessel and the tubular body to allow fluid to flow into and out of the fluid chamber via the fluid conduit; and driving fluid along the fluid conduit alternately into and out of the fluid chamber of the blood pump, thereby enabling the blood pump to pump blood along the blood passageway. Other preferred features of the present invention are set out in the appended claims.

420268 BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 is a schematic diagram of the heart with an enlarged partial view showing a section of the aorta into which a pulsatile blood pump according to one embodiment of the present invention may be inserted;

Figure 2 is a lateral cross-sectional view of a pulsatile blood pump according to one embodiment of the present invention;

Figure 3 is an axial cross-sectional view of the pulsatile blood pump of Figure 2;

Figure 4 is a schematic representation of a blood pump system

incorporating the pulsatile blood pump of Figure 2;

Figure 5 shows a fluid conduit to convey fluid into and out of a fluid chamber of the pulsatile pump of Figure 2;

Figure 6 shows a lateral cross-sectional view of an embodiment of a pulsatile blood pump having a built-in one-way check valve;

Figure 7 shows a schematic perspective view of a pulsatile blood pump according to an embodiment of the present invention which incorporates non- stretch filaments into the tubular body of the blood pump;

Figure 8 shows two lateral cross-sectional views of pulsatile blood pumps according to embodiments of the present invention, both of which configured are to pump blood in a preferred direction shown by the arrow B;

Figure 9 shows four lateral cross-sectional views of pulsatile blood pumps according to embodiments of the present invention showing different ways of attaching a flexible membrane of the pump to the tubular body of the pump;

Figure 10 shows an axial cross-sectional view of an alternative

embodiment of a pulsatile blood pump with a different configuration of the flexible membrane within the tubular body;

Figure 11 shows schematic perspective views of pulsatile blood pumps according to embodiments of the present invention showing three ways of incorporating deformable elements into the tubular bodies of the blood pumps; and

420268 Figure 12 shows the pulsatile blood pump of Figure 2 with its tubular body in the collapsed configuration during catheter delivery.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Figure 1 shows a schematic representation of a human heart . A healthy heart 1 pumps blood to the body via the aorta 2. According to a preferred embodiment of the present invention, a pulsatile blood pump is placed within a portion 3 of the aorta 2 just distal of the aortic root and the remainder of the heart 1 , as shown in the enlarged view 4 of Figure 1. It will be appreciated that other placement sites of the blood pump 10 within a patient's vascular system are also possible. Having been placed within the preferred blood vessel, the blood pump 10 may then be activated intermittently for short periods as required, or may be activated continuously for periods of limited or unlimited duration. Therefore, this embodiment of the present invention provides a small pulsatile blood pump 10 having a volume of between 10 and 70ml_ which may be temporarily or permanently incorporated into the aorta 2 (or elsewhere) as an active graft.

A blood pump 10 in accordance with an embodiment of the present invention will now be described in more detail with reference to Figure 2 which shows such a blood pump 0 in situ within the aorta 2 of a human patient. The blood pump 10 comprises a substantially tubular body 12 and a flexible membrane 14. The tubular body 12 further comprises deformable elements 80, 82, 84 as will be described in more detail below with reference to Figure 11 .

The tubular body 12 has a first end 18 and a second end 20. In use, the tubular body 12 is tightly disposed within a section of the aorta, with the external surface of the tubular body 12 pressed up against the internal wall of the aorta such that blood flows through the tubular body 12 in a direction substantially away from the heart 1 from the first end 18 of the tubular body 2 towards the second end 20 as shown by the arrow B. The tubular body 12 is disposed coaxially within the aorta 2.

The tubular body 12 is formed from a flexible, gas-impermeable material which may be collapsed during delivery of the blood pump 10. A suitable material might be polyethylene terephthalate (e.g. Dacron™) or woven PTFE

420268 impregnated with silicone or other material to make it gas-tight. The tubular body has an expanded configuration for use when the blood pump 10 is in use, and a collapsed configuration for use during delivery of the blood pump 10 to the desired blood vessel. The tubular body 12 comprises deformable elements which act to stiffen the flexible tubular body 12 to retain it in its expanded, tubular configuration (i.e. having a substantially circular cross section) when disposed in situ in the aorta 2. In other words, the deformable elements are present to hold open the lumen of the tubular body 12 in use, and to prevent the collapse of the tubular body 12 in the absence of significant external forces. In fact, the deformable elements will prevent the collapse of the tubular body 12 even if there are reasonable external forces on the tubular body from the lumen or from surrounding tissue. Nonetheless, the deformable elements are deformable (rather than rigid) so as to enable the tubular body 12 to be deformed or collapsed during catheter delivery of the blood pump 10 to the desired blood vessel. The deformable elements effectively form a stent such that the tubular body 12 and the deformable elements together form a stent graft. The

deformable elements may be superelastic (e.g. formed from a material such as nickel titanium) to provide the required stiffness during use of the blood pump 10, but other materials are also readily envisaged.

Figure 1 1 shows three different embodiments of the deformable elements

80, 82, 84. In each case, the deformable elements 80, 82, 84 are formed as wires in particular configurations. The deformable elements 80 in Figure 1 1a form rings of zig-zags around the tubular body 12, with all the rings of zig-zags being in phase with one another. The deformable elements 80 are attached to the tubular body 2 at the apexes 81 of the zig-zag formations. The deformable elements 82 in Figure 1 1 b again form rings of zig-zags around the tubular body 12, but each ring of zig-zags is in anti-phase with the two adjacent rings of zigzags. Again, the deformable elements 82 are attached to the tubular body 12 at the apexes 83 of the zig-zag formations. The deformable elements 84 in Figure 11c form a net structure or diamond mesh around the tubular body 12. The deformable elements 84 are attached to the tubular body 12 at the corners 85 of each diamond shape. The deformable elements 80, 82, 84 are advantageously

420268 - I n disposed on the external surface of the tubular body 12 so as to avoid

interference with the movement of the flexible membrane 14. Alternatively, the deformable elements 80, 82, 84 could be disposed on the internal surface of the tubular body 12 or at least partially within the structure of tubular body 12. Many other configurations of deformable elements would be appropriate for the blood pump 10, as will be evident to one familiar with stent design. Thus the simple examples shown in Figure 11 are not intended to be limiting.

Returning to Figure 2, the flexible membrane 14 is formed as a tube and is attached concentrically within the tubular body 12 so as to line an inner surface 24 of the tubular body 12. Thus, a fluid chamber 22 is formed between the flexible membrane 14 and the inner surface 24 of the tubular body 12. The fluid chamber 22 is therefore partially bounded by the flexible membrane 4 and partially bounded by the inner surface 24 of the tubular body 12. A blood passageway 26 extends between the first and second ends 18 and 20 of the tubular body 12 and is at least partially bounded by the flexible membrane 14. Thus, the flexible membrane 14 separates the fluid chamber 22 from the blood passageway 26. This is most clearly seen in the axial cross-sectional view of the blood pump 0 of Figure 3 which is a view looking along the axis of blood flow that shows the blood passageway 26 disposed concentrically within the fluid chamber 22.

A fluid conduit 28 passes through the aorta wall and the wall of the tubular body 12 to enable fluid to flow into and out of the fluid chamber 22 of the blood pump 10. Thus, the fluid conduit 28 carries fluid towards and away from the fluid chamber 22 of the blood pump 10.

A blood pump system 34 incorporating the blood pump 10 of the present invention is shown schematically in Figure 4. The blood pump 10 (not to scale) is shown implanted within the patient's body 32. The fluid conduit 28 is shown to exit the patient's body 32 percutaneously at the exit site 36. A pressure sensor 39 may be provided to measure the pressure within the fluid conduit 28 close to the blood pump 0. Alternatively or additionally, a pressure sensor (not shown) may be incorporated into the tubular body 12 of the blood pump 10 to measure pressure within the fluid chamber 22.

420268 The fluid conduit 28 terminates at the tubular body 12 of the blood pump 10. The fluid conduit is transverse to the tubular body 12. For example, as shown in Figure 4, the fluid conduit 28 is substantially perpendicular to the tubular body 12. The fluid conduit 28 is attached to the tubular body 12 of the blood pump 10 in such a way that it may not become detached accidentally. For example, the connection may have a locking mechanism. The connection between the fluid conduit 28 and the tubular body 12 may also be detachable such that the fluid conduit 28 may be easily replaced if it becomes infected.

Barbed, snap-lock or screw connectors may all be appropriate methods of connection here, along with others. The connection of the fluid conduit 28 to the tubular body 12 may be made after placement of the blood pump 10 into the blood vessel. This requires an additional minimally invasive surgical procedure wherein a tunnel is made in the patient's tissue from the exit site 36 to the outer surface of the tubular body 12, Hence the connection has a design which allows and facilitates connection in-situ. An alternative method of connecting the fluid conduit 28 to the tubular body 12 in-situ envisaged here is facilitated by the use of a special tool which follows the tunnel in the patient's tissue and which punctures the tubular body 12 in-situ making a port 96. The connection may then be made by surgically sewing the fluid conduit 28 to the tubular body 12 at the site of the port 96 or by deploying a connector which is pre-installed on the end of the fluid conduit 28 or is installed just prior to insertion of the fluid connector 28. The fluid conduit 28 is flexible and biocompatible. Silicone or PVC are examples of materials appropriate for its construction.

It is desirable to assist tissue incorporation into the exit site 36 so as to prevent infection tracking up the portion of the fluid conduit 28 within the patient's body 32. This may be achieved by wrapping a biocompatible and porous material 38 around the fluid conduit 28 at the exit site 36. Woven or felt polyester or polytetrafluoroethylene (PTFE) may well be best suited to this purpose. As shown in Figure 4, the material 38 is wound around the fluid conduit 28 right at the exit site 36 so as to become incorporated into the patient's body tissue. The material 38 might extend along a substantial portion of the fluid conduit 28 even

420268 up to the pump 10 so as to allow a substantial degree of tissue incorporation and resistance to infection tracking.

A distal end of the fluid conduit 28 is coupled to a drive unit 30 which is an electromechanical device operable to drive fluid alternately into and out of the fluid chamber 22 via the fluid conduit 28. The drive unit 30 may be a

conventional console similar to those used in known lABPs when the patient is confined to bed (e.g. when the patient is hospitalised). However, since there is no femoral cannula, the patient is ambulatory and treatment could be delivered in a surgical ward or even in a hostel or at home rather than in an intensive or cardiac care unit. Alternatively, the drive unit 30 may be a small battery powered wearable device so that patients can be treated completely untethered.

The fluid may be a liquid or a gas, so that the drive unit 30 is operable to provide pulses of hydraulic or pneumatic fluid flow into the fluid conduit 28. In preference the fluid would be helium, but it is envisaged that the pneumatic fluid might be air, carbon dioxide, or any readily available non-toxic gas. A hydraulic fluid might be water or any readily available non-toxic liquid.

Figure 4 additionally shows an optional connector 40 which forms part of the fluid conduit 28 between the exit site 36 and the drive unit 30. In periods where the blood pump 10 is not in use, the drive unit 30 may be disconnected from the blood pump 0 by means of this connector 40. In Figure 4, the connector 40 is disposed just outside the surface of the skin (i.e. just outside the patient's body 32). Alternatively, the connector 40 may be implanted just below the skin surface of the patient's body 32. In either case, the use of the connector 40 allows the portion of the fluid conduit 28 outside the patient's body 32 to be easily replaced should it become damaged. It is envisaged that, in a

configuration in which the connector 40 is placed below the skin, the skin would be allowed to heal over the connector 40 if the blood pump 10 is not actuated for a long period of time and that, on withdrawal of the extracorporeal section of the fluid conduit 28, the connector 40 would self-seal. Reconnection would be made by puncturing the skin overlying the connector 40 and breaching the self-sealing mechanism.

420268 Also shown in Figure 4 is a control unit 42, which may be a computer, and which is programmable and operable to run software 44 to control the drive unit 30. Thus, there is provided a cable 46 coupled between the drive unit 30 and the control unit 42 to allow data communication therebetween. The control unit 42 may be used to set up controllable parameters of the drive unit 30 and/or to download patient and blood pump data which may be stored on the drive unit 30. Either the drive unit 30 or the control unit 42 might be able to communicate with a remote computer or network 48 so as to remotely configure the system 34 or to monitor its performance and/or patient data. Communication with the remote computer or network 48 is via telecommunication means 50 such as a telephone line, Internet connection, Bluetooth, Wi-Fi or similar.

One embodiment of the fluid conduit 28 is shown in more detail in Figure 5. The fluid conduit 28 comprises an outer layer 52 disposed substantially concentrically around an inner tube 54. The outer layer 52 is an armouring layer which enables the fluid conduit 28 to withstand a degree of mechanical loading (e.g. twisting, flexing, tension and/or crushing) without sustaining any significant damage. The inner tube 54 conveys the hydraulic or pneumatic fluid from the drive unit 30 to the fluid chamber 22 of the blood pump 10. A data cable 56 is disposed between the outer layer 52 and the inner tube 54. The data cable 56 provides data communication between the blood pump 10 and any pressure sensors (e.g. pressure sensor 39), ECG sensors, or implanted devices. In an alternative embodiment, the data cable 56 may be disposed within the inner tube 54. Advantageously, since the fluid conduit 28 is not disposed in the patient's blood stream, it poses a much reduced risk of infection than does an IABP cannula.

During delivery, the blood pump 10 is delivered to the desired position in a patient's blood vessel using a catheter. During catheter delivery, the tubular body 12 assumes a collapsed state in which the deformable elements 80, 82, 84 are also collapsed. Figure 2 shows the blood pump 10 with its tubular body 12 in the collapsed configuration during catheter delivery. The catheter is not shown in Figure 12.

420268 In Figure 12, the blood pump 10 is being surgically introduced into the heart 1 through a hole 90 in the apex of the left ventricle. The hole 90 is crafted via a small surgical incision. Figure 12 shows a guidewire 92 inserted through the hole 90 such that the guidewire 92 extends through the aortic valve 94 and into the lower ascending aorta 2. The blood pump 10 is slid along the guidewire 92 into place within the ascending aorta 2 whereupon it is deployed (e.g. by balloon). During deployment, the tubular body 12 moves from its collapsed configuration to its expanded configuration. Following deployment, the catheter (not shown) and guidewire 92 are withdrawn. The hole 90 in the apex of the left ventricle is then closed surgically. Other techniques are readily envisaged for delivery of the blood pump 10, as are other access sites through the heart 1 , including the left atrium. Alternatively the blood pump 10 may be delivered on a catheter which is introduced through any number of access routes, e.g. via the subclavian or femoral arteries.

In use, the blood pump 10 pumps blood along the blood vessel within which it is situated. The drive unit 30 alternately develops relatively high and low pressures which cause pneumatic or hydraulic fluid to flow along the fluid conduit 28 into and out of the fluid chamber 22 of the blood pump 0. The ingress and egress of pneumatic or hydraulic fluid from the fluid chamber 22 is indicated by double-headed arrow A in figure 2. When the drive unit 30 develops a relatively high pressure, fluid is driven hydraulically or pneumatically along the fluid conduit 28 and into the fluid chamber 22. The pressure of the fluid ingress flexes the flexible membrane 14 such that the volume of the inner chamber 22 increases. In particular, the flexible membrane 14 is forced away from the inner surface 24 of the tubular body 12 and the tubular flexible membrane 14 contracts

concentrically. Consequently, there is a decrease in the radius and volume of the blood passageway 26 through the centre of the tubular body 12 of the blood pump 10, and this decrease in volume forces blood preferentially out of the second end 20 of the tubular body 12 in the direction shown by arrow B, though some blood will be driven in the opposite direction past the first end 18 and will augment blood flow to the coronary arteries. When the drive unit 30 develops a relatively low pressure, fluid is driven hydraulically or pneumatically out of the

420268 fluid chamber 22 and into the fluid conduit 28. In this case, the volume of the fluid chamber 22 decreases and there is a corresponding increase in the volume of the blood passageway 26 such that blood is drawn into the first end 18 (and the second end 20) of the tubular body 12. Thus, the blood passageway 26 remains essentially circular in cross-section during the use of the blood pump 10, but the diameter of the blood passageway 26 increases and decreases with the flexing of the flexible member 14.

Therefore, the fluid chamber 22 is alternately expanded and contracted as the flexible membrane 14 is inflated and deflated by the action of the hydraulic or pneumatic fluid flow from the drive unit 30. In other words, as the flexible membrane 14 is flexed by the flow of fluid into and out of the fluid chamber 22, the cross-sectional area of the blood passageway 26 changes so as to aid in the pumping of blood along the aorta 2. The flexing of the flexible membrane 14 is shown by double-headed arrows C in figures 2 and 3. In this way, the blood pump 10 aids the normal flow of blood through the aorta 2 in the normal flow direction shown by arrow B.

Significant retrograde flow (i.e. flow in the opposite direction to that indicated by arrow B), is prevented by the action of the heart's aortic valve, but small volumes of blood will escape the blood pump 10 in the retrograde flow direction and augment coronary artery perfusion. If the patient's aortic valve is not competent to function, then there are two possibilities. One option is to surgically repair the patient's aortic valve at the time of implantation of the blood pump 10. Alternatively/additionally, the blood pump 0 may itself include a prosthetic heart valve. This option is shown in the embodiment of Figure 6 which shows the blood pump 10 including a check valve 58 (i.e. a one-way flow valve) which only allows blood to flow through the blood passageway 26 of the tubular body 12 in the direction of normal blood flow, as shown by arrow B. The check valve 58 may be included even if the patient's aortic valve is functional. In this case, the additional check valve 58 may further augment the action of the blood pump 10. The check valve 58 may be incorporated into the blood pump 10 at either the first end 18 or the second end 20, or both. The check valve 58 is capable of being collapsed so as to allow catheter delivery whilst incorporated into the blood pump 10 in its collapsed state, or is capable of insertion into the blood pump 10 in an additional (preferably minimally invasive) surgical procedure.

Also shown in Figure 6 are securing devices 98 which protrude from the tubular body 2 and which maintain intimate contact with the inner wall of the aorta 2 so as to hold the blood pump 10 in place against fluid dynamical and other forces which act on the blood pump 10. In a preferred embodiment, the securing devices 98 resemble hooks which bite into the inner wall of the aorta 2, as shown in Figure 6. In an alternative embodiment, the securing devices 98 are absent and the position of the blood pump 10 within the aorta 2 is maintained through the action of deformable elements 80, 82, 84 which, when expanded, bring to bear sufficient frictional forces between the tubular body 2 and the aorta 2 to retain the blood pump 10 in its correct place. (The deformable elements 80, 82, 84 are described further below with reference to Figure 1 1 .) It is also envisaged that sutures (not shown) might also be used to help to maintain correct positioning of the blood pump 10 within the aorta 2.

The pressure sensor 39 (and/or other pressure sensors described above) is used to assist with the timing of the fluid flow into and out of the fluid chamber 22 of the blood pump 10. In particular, the pressure measurements from the pressure sensor 39 (and/or other pressure sensors described above) are relayed to the drive unit 30 and/or the control unit 42. In a preferred embodiment, the contraction of the blood pump 10 is controlled such that it occurs in anti-phase with the contractions of the natural heart 1. In other words, when the heart 1 is in diastole, the blood pump 10 is in systole, and vice-versa. Other measurements may also be used to control the timing and/or amount of fluid flow into and out of the fluid chamber 22. For example, an electrocardiograph (not shown) may additionally be provided to monitor electrocardiographic data from the patient's heart. In this case, the drive unit 30 and/or the control unit 42 may be coupled to the electrocardiograph to receive the measured data. The drive unit 30 and the control unit 42 may be separate devices as shown in Figure 4, or may

alternatively be part of a single integral device, which may be portable and wearable by a patient, as described above.

420268 The beneficial effect of the blood pump 10 of the present invention on the heart 1 derives from the aorta 2 being partially "emptied" and more readily distensible with the next cardiac ejection. This reduces the amount of work the heart 1 has to do and allows a degree of recovery and demodelling (reverse remodelling) of the myocardium. It is envisaged that the blood pump 10 would operate for a support period of around two weeks, after which the blood pump 10 would will be turned off and remain dormant until the next programmed or emergency support period. Experience with related devices suggests no ill effects in the period of dormancy.

The blood pump 0 is implanted operatively. This provides the opportunity for a surgeon to anatomically correct the underlying cardiac defect leading to heart failure (e.g. valve disease, coronary artery disease, cardiomyopathies). This is preferentially carried out through minimally invasive procedures. This defect correction, when combined with the subsequent intermittent use of the blood pump 10, should significantly improve the patient's prognosis.

Furthermore, the operation costs are likely to be significantly lower than the cost of inserting an LVAD, and recovery periods are likely to be much shorter. The flexible membrane 14 is impermeable to the hydraulic or pneumatic fluid used to inflate and deflate the fluid chamber 22. In embodiments where the fluid chamber is partially bounded by the tubular body 12 (e.g. see Figures 9a to 9c), the tubular body 2 is also impermeable to the hydraulic or pneumatic fluid used to inflate and deflate the fluid chamber 22. However, in a preferred embodiment shown in Figure 9d, the fluid chamber 22 is not partially bounded by the tubular body 12. Instead, the fluid chamber is entirely bounded by the flexible membrane 14, except at the entry point formed by the fluid conduit 28. In this case, the tubular body 12 need not be impermeable to the hydraulic fluid used to inflate and deflate the fluid chamber 22. In this way, more traditional materials such as bovine collagen impregnated woven PTFE may be used without being impregnated with silicone or other material to make the tubular body 12 impermeable.

420268 In a preferred embodiment, the flexible membrane 14 is stretchable (i.e. distendable/elastic/resilient). Alternatively, the flexible membrane 14 may simply be flexible (i.e. bendy but not stretchy). However, a stretchable flexible

membrane 14 is preferred so as to reduce the chance of parts of the flexible membrane 14 blocking the blood passageway 26 when the fluid chamber 22 is almost empty of fluid. The flexible membrane 14 may be fabricated from silicone or another biocompatible flexible and distensible material.

Even in the expanded configuration, the tubular body has a degree of flexibility to allow it to bend with each heartbeat. Flexibility of the tubular body 12 is also important so that the blood pump 10 does not interfere with or erode neighbouring structures. In one embodiment, the tubular body 12 of the blood pump 10 is fabricated from polyester (e.g. woven polyester fibre) or

polytetrafluoroethylene (PTFE). Alternatively, the tubular body 12 may be fabricated from silicone, but any biocompatible material might be appropriate.

It will be appreciated that the degree of flexibility of the tubular body 2 in the expanded configuration should be less than that of the flexible membrane 14. This relative lack of flexibility of the tubular body 12 ensures that it is the flexible membrane 14 which deforms due to the flow of fluid into and out of the fluid chamber 22, rather than it being the tubular body 2 which deforms in response to the fluid flow. In use, the volume of the tubular body 12 remains substantially constant during the flow of fluid into and out of the fluid chamber 22. Thus, the deformation of the flexible membrane 14 allows the volume (and the cross- sectional area) of the blood passageway 26 to vary in use so that the blood pump 10 pumps blood.

In order to provide the tubular body 12 with controlled flexibility, the tubular body 12 may comprise a flexible material and may also incorporate relatively non-stretchable elements such as carbon, carbon fibre or Kevlar fibres, filaments, windings, metallic springs, or similar to constrain the tubular body 12 axially.

These non-stretchable elements may be applied in a variety of orientations including axial filaments 62 as shown in Figure 7. Other configurations of non- stretchable elements are also envisaged within the scope of the invention. For example, it may be desirable to provide the tubular body 12 with relatively non- 420268 stretchable elements to constrain the tubular body 12 axially and/or radially. However, it is important that the radial collapsibility of the tubular body 12 for delivery not be compromised by the relatively non-stretchable elements.

In preferred embodiments, the blood pump 10 preferentially pumps blood along the blood passageway 26 in a particular axial direction. The blood pump should then be implanted in the patient's blood vessel in the correct orientation such that the preferential pumping direction corresponds to the normal direction of blood flow along the blood vessel. This normal direction of blood flow is from the first end 18 towards the second end 20 of the tubular body 12 as shown by arrow B in the Figures. Figures 8a and 8b show lateral cross sections of pumps having a preferential pumping direction along arrow B.

In Figures 8a and 8b, the end of the fluid conduit 28 is not centrally disposed along the length of the tubular body 12 in an axial direction. In particular, the end of the fluid conduit 28 is located off-centre along the length of the tubular body 12 such that it is nearer the first end 18 than the second end 20. Thus, as hydraulic or pneumatic fluid flows into the fluid chamber 22, it fills the fluid chamber in a direction from the first end 18 towards the second end 20. This in turn imparts momentum to the blood within the blood passageway 26 in the preferred direction from the first end 18 towards the second end 20 as indicated by arrow B. Thus, the blood pump 10 preferentially pumps blood along the blood passageway 26 from the first end 18 towards the second end 20. In other words, once the blood pump 10 has been implanted in a patient, the end of the fluid conduit 28 is located proximally to preferentially pump blood in a proximal-to-distal direction.

In Figure 8b, baffles 66 are additionally provided within the fluid chamber

22. The baffles 66 are flexible and collapsible and are formed in a spiral configuration so as to further constrain the hydraulic or pneumatic fluid to flow in the preferred direction from the first end 18 towards the second end 20. In particular, the baffles 66 serve to constrain the flow of fluid within the fluid chamber 22 such that fluid does not reach the second (far) end of the fluid chamber until the first (near) end of the fluid chamber has been filled with fluid.

420268 This again imparts momentum on the blood within the blood passageway 26 in the preferred direction indicated by arrow B.

Figure 9 depicts four different ways of attaching the flexible membrane 14 to the tubular body 12. In each of Figures 9a, 9b and 9c, the flexible membrane is attached at/near the first and second ends 18 and 20 of the tubular body so as to form a sealed watertight/airtight fluid chamber 22 within the tubular body 2. The fluid chamber 22 in each of Figures 9a, 9b and 9c is bounded partially by the flexible membrane 14 and partially by the inner surface 24 of the tubular body 12. Thus, in these configurations, both the flexible membrane 14 and the tubular body 12 should be impermeable to the pneumatic or hydraulic fluid pumped into and out of the fluid chamber 22. In Figure 9d the flexible membrane 4

completely encloses the fluid chamber 22 (except for the incorporation of the port 96 to allow for the ingress and egress of pneumatic or hydraulic fluid into fluid chamber 22). Thus, in this configuration, only the flexible membrane 14 need be impermeable to the pneumatic or hydraulic fluid pumped into and out of the fluid chamber 22.

The configuration shown in Figure 9a is the same as that shown in Figures 2, 6 and 8. In particular, the flexible membrane 14 is attached to the tubular body 12 such that the flexible membrane 14 runs essentially parallel to the tubular body 12 in the attachment regions 68 of the flexible membrane 14 to the tubular body 2. Thus, the tubular flexible membrane 4 essentially sits flush to the inner surface 24 of the tubular body 12 when the fluid chamber 22 is empty. In Figure 9a, the active region 70 of the blood pump 10 does not extend along the full axial length of the tubular body 12 since the attachment regions 68 of the flexible membrane 14 to the tubular body 12 are located near, but not at, the ends 18 and 20. In an alternative embodiment, the tubular flexible membrane 14 could be the same length as the tubular body 12 such that the attachment regions 68 would be at the ends 18 and 20 of the tubular body 12 and the active region 70 would extend along the full axial length of the blood pump 10.

In the configuration of Figure 9b, the flexible membrane 14 is folded over such that the tubular flexible membrane 14 doubles back on itself in the attachment regions 68. Thus, there is a double thickness of the flexible

membrane 14 in the attachment regions 68.

A further alternative configuration is shown in Figure 9c in which the flexible membrane 14 extends out of each end 18 and 20 of the tubular body 12. Thus, the attachment regions 68 are at each end 18 and 20 of the blood pump 10.

In Figure 9d, the flexible membrane 14 fully encloses the fluid chamber 22. In this configuration, the flexible membrane 14 is preferentially attached to the tubular body 12 at the first end 18 and at the second end 20. There may also be attachment between the flexible membrane 14 and the tubular body 12 along the entire length of the interface between the flexible membrane 14 and the inner wall of the tubular body 12. Alternatively, there may just be attachment along parts of this interface.

An optimum configuration for attachment of the flexible membrane 14 to the tubular body 12 yields less stress on the flexible membrane 14, the

attachments regions 68 and the tubular body 12. This reduces the likelihood of thrombus formation and blood-flow disturbance, and thereby increases longevity and biocompatibility of the blood pump 10. Depending on the situation, the optimum configuration may be accomplished with any combination of the attachments shown in Figures 9a-9c, and the attachment methods may be dissimilar at the first and second ends 18 and 20. Alternatively the optimum configuration might be accomplished through the configuration shown in Figure 9d which incorporates a flexible membrane 14 which fully encloses the fluid chamber 22.

As shown in Figure 10, the flexible membrane 14 may be formed as a sheet rather than as a tube. In this embodiment, the flexible membrane 14 is disposed in a chord-like manner across the circular cross-section of the tubular body 12. The appropriate chord is shown by dashed line XX' in Figure 0. Thus, the flexible membrane 14 divides the tubular body 12 into two axial

compartments, one of which is the fluid chamber 22, and the other of which is the blood passageway 26. Of course, the flexible membrane 14 is also attached to the tubular body 12 at or near the ends 18 and 20 or forms a complete enclosure W

- 26 - of the fluid chamber (akin to the approach shown in Figure 9d) such that the fluid chamber 22 is completely enclosed and the pneumatic or hydraulic fluid is separated from the patient's blood by means of the flexible membrane 14. In this embodiment, the fluid chamber 22 expands and contracts eccentrically, rather than concentrically as in the embodiment of Figures 2 and 3. Concentric actuation allows the greatest displacement of blood for a given size of blood pump 10. Eccentric actuation may be desirable in some anatomical locations where concentric actuation would obstruct important features, e.g. at the root of the ascending aorta where concentric actuation may obstruct the coronary arteries.

The present invention therefore extends the modality or method for treatment of heart failure which has been termed Chronic Intermittent Mechanical Support (CIMS) by the inventors. The original CIMS system is described in WO2009/040560. Benefits of the present CIMS approach are summarised below: a) Because of the ability to collapse the blood pump 10 to enable it to be

catheter delivered, it may be inserted without resecting a portion of the aorta, as was needed in the original CIMS patent application

WO2009/040560. Additionally it may be implanted into the patient's arterial or venous systems through minimally invasive surgery. It is possible to collapse the present invention to allow it to be removed if desirable, e.g. if demodelling were so complete that the need for the device was removed, and no detriment will be suffered by the section of aorta into which the present invention was implanted.

b) The present CIMS approach includes an embodiment (Figure 9d) in which the flexible membrane 14 fully encloses the fluid chamber 22 and which will therefore not require the material of the tubular body 12 to itself be impregnated with a material which will be impermeable to the hydraulic or pneumatic fluid.

c) The present CIMS approach includes a port 96 which allows connection of the fluid conduit 28 to the tubular body 12 being cut into the the tubular body through minimally invasive surgical procedures whilst the blood pump 10 is in situ in the blood vessel.

d) The present CIMS approach uses securing devices 98, or the action of deformable elements 80, 82, 84, or sutures to maintain the blood pump 10 in its correct position within the aorta 2.

e) The present CIMS approach includes a connector 40 just under the

patient's skin which is able to self seal on removal of the percutaneous section of fluid conduit 28 when the blood pump 10 is to remain dormant for an extended period of time.

f) The present CIMS approach may include a check valve 58 preferentially placed at the first end 18 or the second end 20 of the blood pump 10. In this case, the check valve 58 may be collapsible so as to allow it to be placed in situ via catheter delivery and through minimally invasive surgical procedures.

g) The present CIMS approach makes clear the benefits of retrograde flow from the blood pump 10 in augmenting coronary artery perfusion.

In addition the present CIMS approach retains all of the benefits of the previous CIMS device described in WO2009/040560: h) One main benefit of the CIMS approach will be to improve perfusion to the head, coronary arteries and systemic circulation, and to unload the natural (diseased) heart and allow it to recover through a process known as demodelling or reverse-remodelling. Some hearts will recover almost completely allowing CIMS to be discontinued though the blood pump 10 will remain in place in case of relapse. Other hearts will not recover and medical therapies will continue, but will benefit from CIMS as a therapy similar to, but more aggressive than medical respite.

i) Counter-pulsation is a proven and dependable support method which is incorporated into a large number of commercial lABPs and which is also being developed in EABPs.

420268 j) The use of the percutaneous fluid conduit 28 removes the need for cannulation to support the blood pump 10. This has a number of advantages: it reduces the likelihood of septicaemia posed by lABPs; it ameliorates ischemia distal to the insertion point of the cannula; it removes thromboembolic complications caused by tracking a cannula through the veins; and, unlike lABPs, it allows patients to ambulate,

k) Ease of deployment: since the blood pump 10 is delivered via a catheter, and the present system provides the option of insertion of the blood pump via minimally invasive surgery.

I) Reduction of trauma to the aorta by removing the constant interaction

between the balloon of an IABP/EABP and the inner surface of the aorta, which can cause abrasion to the endothelium and lead to plaque

formation, aneurism and thrombosis and rupture of the aorta,

m) Elimination of atheromatous emboli: unlike EABPs, the blood pump 10 will not act eccentrically within an atherosclerotic section of aorta, and will remove the mechanisms which lead to the formation atheromatous emboli, n) Reduction in the amount of surface area of non-biological materials

lessens the likelihood of: infection, consumption of coagulation products (e.g. platelets), and bleeding.

o) The blood pump 10 has distinct advantages over EABPs in that it cannot migrate and will not interfere with neighbouring structures (e.g. causing erosion of the pulmonary artery). Positioning a CI MS blood pump 10 within the aorta 2 also gives greater flexibility in the profile design and the use of an eccentric blood pump 10 will enable CIMS to be used where Coronary Artery Bypass Grafting (CABG) is necessary.

p) Cost: the cost of LVAD interventions in bridge to transplantation and

destination therapy (Long Term Chronic Support, or LCTS) in terms of Quality-Adjusted Life-Year (QALY) is unacceptably high at an envisaged £40,000/QALY for second generation devices. Given the complexity of second and third generation LVADs, it is unlikely that their cost will reduce to acceptable levels of around £20,000/QALY. Given that the QALY for CIMS is likely to be between those of medical and LVAD therapies and

420268 that operating, recovery, and device costs are envisaged to be significantly lower, CI MS offers the potential for long-term cardiac support at acceptable cost (E/QALY). It is entirely feasible that the blood pump 10 and system 34 of the present invention may be adapted for use in other blood vessels (e.g. a peripheral vein or artery) to increase regional or peripheral perfusion of organs or tissue. One example might be insertion of a blood pump 10 into the femoral or popliteal arteries for the treatment of intermittent claudication, or into the subclavian artery to augment central arterial blood flow and pressure. Alternatively, this technique could be used to provide ventricular unloading and pressure augmentation in the major vessels and flow augmentation in the coronary artery through action in a near-distal artery such as the subclavian artery. Although preferred embodiments of the invention have been described, it is to be understood that these are by way of example only and that various modifications may be contemplated.

420268