Cardiac assist device

A cardiac assist device (100) comprises a stent 103, 403) which is implantable into a blood vessel of a patient. The stent (103, 403) encloses an inner volume (119, 419). At least one inflatable element (104, 409-413) is attached to the stent (103). The at least one inflatable element (104, 409-413) is provided in the inner volume (119, 419) of the stent (103, 403), wherein the ai least one inflatable element (104, 409-413) annularly encloses a central opening (118, 418) being parallel to a longitudinal axis of said stent (103, 403). The cardiac assist device (100) further comprises a fluid supply adapted for periodically inflating and deflating the at least one inflatable element (104, 409-413), wherein said fluid supply comprises at least one fluid supply line (105, 405) connectable to the at least one inflatable element (104, 409-413) and implantable into a blood vessel of the patient.

FIELD OF THE INVENTION

The present invention generally relates to the filed of cardiac assist devices, in particular to a cardiac assist device which may be implanted at least partially into a blood vessel of a patient to assist the heart of the patient in pumping blood through the circulatory system, to decrease the afterload of the heart, to increase the native ejection fraction and/or to improve the coronary perfusion and the oxygen supply to the myocardium.

BACKGROUND OF THE INVENTION

In patients suffering from heart failure which may, for example, be caused by a myocardial infarction, a dilatative or ischemic cardiomyopathy or another disease, the capability of the heart to pump blood through the patient's circulatory system may be reduced to a large extent. Hence, blood supply to vitally important organs may be reduced, which may directly or indirectly lead to death of the patient.

Heart failure may be treated by means of a heart transplantation, wherein the patient's heart is replaced by a donor heart which is obtained from a brain dead person. Transplant organs, however, may be rare, and a careful selection of the transplant organ is required in order to avoid a rejection of the transplant organ by the immune system of the patient. Hence, a considerable amount of time may pass until a transplant organ suitable for the patient can be found, which amount of time may be too long to save the patient's live. More than 50% of the candidates for a heart transplantation die while they are registered on the waiting lists for a heart transplantation. Furthermore, there are many contraindications for heart transplantation such as old age, infections and longstanding high pulmonary pressure.

Therefore, it has been proposed to replace or assist the patient's heart by mechanical devices, at least temporarily while the patient is waiting for a suitable donor (“bridge to transplant”). Besides artificial hearts, which are designed to completely replace the patient's heart, cardiac assist devices have been proposed which support the action of the native heart.

In one example of a cardiac assist device according to the state of the art, an atrium of the patient's heart may be cannulated, and the cannula may be connected to a pump. Thus, blood can be pumped out of the atrium, and may be injected into a further cannula connected to an artery of the patient, wherein the artery chosen depends on whether the left or the right ventricle is supported by the cardiac assist device. The right ventricle of the heart may be supported by cannulating the right atrium and the pulmonary artery. The left ventricle may be assisted by cannulating the left atrium and the aorta.

A problem of cardiac assist devices according to the state of the art is that connecting the cardiac assist device to the circulatory system of the patient may require open heart surgery, which may imply a high risk of complications.

WO 00/35515 discloses an intravascular cardiac assist device that comprises an elongated tubular member adapted for insertion into a blood vessel, such as a pulmonary artery, the tubular member comprising a lumen defining a perfusion path within the vessel through the tubular member, an inlet port, an outlet port, an optional inlet valve associated with the inlet port and an optional outlet valve associated with the outlet port, and an inflatable member positioned in the lumen and selectively movable between a deflated position and one or more inflated positions during which blood is propelled from the inlet port axially through the lumen and back into the vessel through the outlet port and the optional outlet valve. The device is implanted through an incision in the blood vessel, and fluid is supplied to the inflatable member by means of a flexible inflation/deflation lumen inserted through the incision.

A problem of the intravascular cardiac assist device disclosed in WO 00/35515 is that the incision in the blood vessel, which is required to inflate and deflate the inflatable member, limits the application of the device to providing cardiac assist during heart surgery, and for providing post-operative support. However, the device is not suitable for providing cardiac assist for a longer period of time, for example until a donor heart for the patient is available.

WO 00/53240 discloses a balloon pump system including a catheter-mounted pumping balloon configured to be positioned within a desired body passageway to pump a fluid, for example blood, through the body passageway. A stent is percutaneously deployed within the body passageway. The pumping balloon is percutaneously deployed within the stent such that the stent is interposed between the pumping balloon and the walls of the body passageway.

A problem of the system disclosed in WO 00/53240 is that the pumping balloon provides an obstacle to fluid flow through the body passageway, even if the balloon is in its deflated state. Moreover, in the deflated state of the balloon, the balloon may have an irregular surface. Thus, turbulences may be created in the blood flow, which may lead to the formation of thrombi. It has been observed that the formation of thrombi may start within about 24 hours after the implantation of a balloon pump, and may lead to a significant risk of complications within about two weeks after the implantation of the balloon pump. Such complications may include peripheral thrombosis, infections, dysfunctions of the balloon pump, and embolism. Therefore, the device of WO 00/53240 may be used only for a relatively short period of time in exceptional situations.

It is an object of the present invention to provide a cardiac assist device which may assist the patient's heart, and which may be used without there being a requirement of open heart surgery for implantation of the device.

It is a further object of the present invention to provide a cardiac assist device which may be used for a relatively long period of time for providing a bridge to transplant, and for providing cardiac assist for an extended period of time to patients wherein counterindications such as old age, infections and longstanding high pulmonary pressure make a heart transplant difficult or almost impossible.

SUMMERY OF THE INVENTION

According to the present invention, this problem is solved by a cardiac assist device comprising a stent. The stent is implantable in a blood vessel of a patient and encloses an inner volume. At least one inflatable element is attached to the stent. The inflatable element is provided in the inner volume of the stent, and annularly encloses a central opening being parallel to a longitudinal axis of the stent. The cardiac assist device further comprises a fluid supply adapted for periodically inflating and deflating the at least one inflatable element. The fluid supply comprises at least one fluid supply line connectable to the at least one inflatable element and implantable into a blood vessel of the patient.

The cardiac assist device can be implanted in a blood vessel of the patient such as, for example, into the aorta or pulmonary artery. For this purpose, the stent can be provided in a collapsed state and the at least one inflatable element can be provided inside the stent in a deflated state. The stent may be connected to a catheter, and may be enclosed by a sheath adapted to prevent a premature expansion of the stent. The catheter, together with the stent and the at least one inflatable element connected thereto, may then be inserted into a blood vessel of the patient, for example a peripheral artery, by means of the Seldinger technique, which is well known to persons skilled in the art. Thereafter, the catheter may be advanced to the aorta or pulmonary artery of the patient. Then, the sheath can be removed to effect an expansion of the stent. The stent may attach to the inner surface of the blood vessel of the patient. Subsequently, the at least one inflatable element may be connected to the fluid supply to be periodically inflated and deflated. The periodic inflation and deflation of the inflatable element may induce or enhance a blood flow through the patient's blood vessel, thus supporting the cardiac action of the patient's heart. Hence, the implantation of the cardiac assist device can be performed in a minimally invasive manner.

The inflatable element which annularly encloses the central opening may exhibit a force to the flowing blood in a substantially radially symmetrical manner. Thus, the flow of blood through the cardiac assist device may be improved. In particular, the annular inflatable element, in its deflated state may have a significantly reduced resistance to blood flow compared to a balloon as described in WO 00/53240. Thus, the risk of complications such as peripheral thrombosis, infections, dysfunctions of the balloon pump, and embolism may be reduced significantly, which may allow to provide cardiac assist for an extended period of time.

The at least one inflatable element may comprise an elastic envelope. The elastic envelope can comprise an inner circumferential portion enclosing the central opening. The inner circumferential portion may have a higher degree of elasticity adjacent a first end of the stent than adjacent a second end of the stent. Thus, in case the inflatable element is inflated by supplying fluid to the inflatable element, at the beginning of the inflation process, the inflatable element may expand to a greater extent in the vicinity of the first end of the stent. In the vicinity of the second end of the stent, due to the lower degree of elasticity of the inner circumferential portion, a higher pressure may be required to expand the inflatable element. Therefore, the inflatable element may first expand at the first end of the stent. If the inflatable element is deflated, the inflatable element will contract to a greater extent in the vicinity of the second end of the stent, since the portion of the elastic envelope having a lower degree of elasticity provides a greater reset force. Thus, the inflatable element may impart a directional motion to the volume of blood inside the cardiac assist device. The cardiac assist device may be implanted such that the first end of the stent is provided closer to the heart (proximal valvular site) of the patient than the second end. Hence, during the inflation, a column of blood inside the cardiac assist device may be pushed away from the patient's heart into the circulatory system. During the deflation, blood may be drawn out of the heart into the cardiac assist device. Thus, the pumping action of the heart can be supported in an efficient manner.

In one embodiment, the inner circumferential portion of the elastic envelope may have a smaller thickness adjacent the first end of the stent than adjacent the second end of the stent. Thus, a higher degree of elasticity adjacent the first end of the stent than adjacent the second end of the stent can be provided in a convenient manner.

In other embodiments, the at least one inflatable element may comprise a plurality of inflatable elements, and the fluid supply can be adapted to successively inflate the plurality of inflatable elements and to successively deflate the plurality of inflatable elements. Due to the successive inflation and deflation, respectively, of the inflatable elements, a directionality may be imparted to the flow of blood, which may allow a particularly efficient support of the pumping action of the patient's heart.

The fluid supply can be adapted to individually inflate and deflate each of the plurality of inflatable elements. Hence, the shape of the space inside the cardiac assist device which is filled with blood and emptied during the deflation and inflation, respectively, of the inflatable elements may be controlled in a particular efficient manner to adapt the action of the cardiac assist device to the individual needs of the patient.

The cardiac assist device may further comprise a heartbeat detector adapted to detect a cardiac action of the patient. Thus, the cardiac action of the patient may be monitored to adapt the operation of the cardiac assist device to the patient's heartbeat. The heartbeat detector may, in some embodiments, comprise a flow sensor, a pressure sensor and/or an electrocardiogram sensor.

The fluid supply can be adapted to synchronize the periodic inflation and deflation of the at least one inflatable element with the cardiac action of the patient. Thus, the at least one inflatable element can be deflated during systole to cause a vacuum in the flow direction which may support an unloading of the ventricle of the patient's heart. During diastole, the inflatable element can be inflated to eject the blood in the flow direction. Additionally, blood may be ejected into the coronary arteries of the patient. This may help to improve a supply of oxygen to the heart.

In some embodiments, the fluid supply may comprise at least one pump. The at least one fluid supply line may connect the at lest one pump and the at least one inflatable element. The fluid supply may further comprise a control unit adapted to control the pump to provide the periodic inflation and deflation of the inflatable element and a power supply connected to the at least one pump and the control unit. Hence, fluid may be pumped into the at least one inflatable element via the at least one fluid supply line by means of the pump to inflate the at least one inflatable element. Additionally, the pump and the at least one fluid supply line may be employed to pump fluid out of the at least one inflatable element in order to deflate the at least one inflatable element. Energy for the operation of the pump and the control unit can be provided by the power supply.

The fluid supply can be implantable into the patient. An implantation of the fluid supply into the patient may help to avoid a risk of infections for the patent, since fluid supply lines and/or electric lines leaving the body of the patient which may allow germs to enter the body of the patient may be avoided. Additionally, the mobility of the patient may be improved, since the patient does not have to be connected to an external device. Fluid supply lines provided in blood vessels of the patient may allow to provide the fluid supply in another part of the patient's body than the stent and the inflatable element. Thus, the fluid supply can be implanted into a part of the patient's body which is easily accessible by surgery and wherein a sufficient amount of space is available. For example, the fluid supply may be implanted pectorally.

The power supply may comprise a rechargeable battery and an induction coil subcutaneously implantable into the patient for recharging the rechargeable battery. The rechargeable battery may provide a power supply which is independent of external power sources. Via the induction coil, the rechargeable battery can be recharged in a convenient manner without requiring an electric line through the patient's skin which might allow germs to enter the patient's body.

The fluid supply may further comprise a fluid reservoir. In the fluid reservoir, fluid which is pumped out of the at least one inflatable element during the deflation of the at least one inflatable element may be stored until the at least one inflatable element is inflated. Additionally, fluid from the fluid supply may be used to balance losses which may be caused, for example, by diffusion through the walls of the at least one inflatable element or other leakages.

In some embodiments, the stent may have a length in a range from about 80 mm to about 100 mm and a diameter in a range from about 25 mm to about 45 mm. Hence, the dimensions of the stent in the expanded state may be adapted for insertion into the patient's aorta and/or pulmonary artery.

The stent may be self-expandable. Due to the individual variation of the diameter of the aorta, a self-expandable stent may fit better to the patient's aorta, and may help to reduce a risk of a rupture of the aorta.

In some embodiments, the at least one inflatable element comprises an elastic envelope that comprises an inner circumferential portion enclosing the central opening, an outer circumferential portion attached to the stent and a first and a second cover portion connecting the inner circumferential portion and the outer circumferential portion. The at least one fluid supply line is attached to the second cover portion. Thus, the fluid supply line may extend from the elastic envelope into a direction substantially parallel to the blood vessel into which the cardiac assist device is implanted, without there being a necessity to strongly bend the fluid supply line. This may facilitate the implantation of the fluid supply line into the blood vessel, and may reduce a resistance of the fluid supply line for fluid flow.

In some embodiments, an area of the second cover portion adjacent the at least one fluid supply line is substantially perpendicular to the longitudinal axis of the stent, at least in an inflated state of the at least one inflatable element. A portion of the at least one fluid supply line adjacent the second cover portion can be substantially parallel to the longitudinal axis of the stent.

In some embodiments, the stent has a collapsed configuration and an expanded configuration. The cardiac assist device further comprises a catheter running through the central opening of the stent and a removable sheath. The sheath is adapted to maintain the stent in the collapsed configuration, wherein the at least one fluid supply line is running through the sheath. The catheter is adapted for being removed after removal of the sheath. As already detailed above, the sheath and the catheter may be used to implant the cardiac assist device in a minimally invasive manner. A method of providing cardiac assist to a patient according to the present invention comprises providing an endovascular portion of a cardiac assist device comprising a stent enclosing an inner volume, at least one inflatable element being attached to the stent and provided in the inner volume of the stent, and a fluid supply line. The at least one inflatable element annularly encloses a central opening parallel to a longitudinal axis of the stent. The endovascular portion is implanted into the patient, wherein the stent and the at least one inflatable element are provided in one of an aorta and a pulmonary artery of the patient. The fluid supply line extends from the one of the aorta and the pulmonary artery to a peripheral blood vessel of the patient. An extravascular portion of the cardiac assist device comprising a fluid supply is provided. The at least one fluid supply line is connected to the extravascular portion. The fluid supply is operated to periodically inflate and deflate the at least one inflatable element.

In some embodiments, the extravascular portion may be implanted into the patient.

In some embodiments, at least a part of the extravascular portion may be pectorally implanted into the patient.

In some embodiments, a donor heart may be transplanted into the patient some time after the implantation of the endovascular portion. The cardiac assist device may be operated until the transplantation of the donor heart.

In some embodiments, the cardiac assist device is operated for at least two weeks.

In some embodiments, a catheter running through the central opening of the inflatable element and through the stent is provided. A sheath is provided over the endovascular portion. The sheath is adapted to maintain the stent in a collapsed configuration. The at least one fluid supply line is running through the sheath. The implantation of the endovascular portion comprises inserting the catheter into the peripheral blood vessel of the patient. The catheter is advanced to the one of the aorta and the pulmonary artery. The sheath is withdrawn to expose the endovascular portion. The stent is expanded into an expanded configuration and the catheter is retraced.

In some embodiments, the sheath is retracted further to expose the fluid supply line.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows a schematic cross-sectional view of a cardiac assist device100according to an embodiment of the present invention. The cardiac assist device100comprises an endovascular portion101and an extravascular portion102. The endovascular portion101is configured for implantation into a blood vessel of a patient. The extravascular portion102may be configured for implantation into other portions of a patient's body.

The endovascular portion101comprises a stent103. Similar to stents adapted for the treatment of aortic dissections known to persons skilled in the art, the stent103may comprise a wire arranged in a zigzag configuration and/or forming a grating, mesh and/or ring and comprising a metal such as, for example, a stainless steel alloy, a cobalt chrome alloy, titanium, tantalum, platinum or gold. In other embodiments, the stent103can comprise a high elastic limit material such as Eligoy. The stent103may have a substantially cylindrical shape, enclosing an inner volume119. An outer diameter and a length of the stent103can be adapted such that the stent can be inserted into an aorta or a pulmonary artery of a patient.

In some embodiments, the stent103can be self-expandable. In such embodiments, the stent103may have an expanded configuration wherein the diameter of the stent is approximately equal to or slightly greater than a diameter of the blood vessel into which the stent103is to be inserted. For example, the stent103in the expanded configuration may have a diameter in a range from about 25 mm to about 45 mm. Hence, in the expanded configuration, the stent103may fit into the blood vessel, and may exhibit a slight pressure to the wall of the blood vessel, which may help to avoid a shifting of the stent103. The stent103further may have a collapsed configuration wherein the stent103has a smaller diameter. The stent103may be brought into the collapsed configuration by radially compressing the stent103, and may be held in the collapsed configuration by means of a sheath enclosing the stent103, as will be explained in more detail below. If the sheath is removed, the stent103may return to its expanded configuration due to elastic forces. In some embodiments, the stent103can have a length in a range from about 80 mm to about 100 mm. A thickness of the stent103in the expanded configuration may have a value in a range from about 1 mm to about 2 mm.

In other embodiments, the stent103may be adapted for expansion from the collapsed configuration to an expanded configuration by means of an inflatable balloon provided in the inner volume119of the stent103, as will be explained in more detail below.

The present invention is not restricted to embodiments wherein the stent103comprises a wire, as described above. In other embodiments, the stent103can have a substantially tubular configuration and may be formed from a plastic material. In such embodiments, the stent103may comprise a plurality of openings formed in its sidewalls.

The endovascular portion101further comprises an inflatable element104. The inflatable element104may comprise an elastic envelope308enclosing an inner volume307of the inflatable element104(FIGS. 3ato3d). A fluid line105may connect the inner volume307of the elastic envelope308to the extravascular portion102of the cardiac assist device100. The elastic envelope308may comprise an elastic material, for example a polymer material such as silicone, polyurethane or gore-tex. A surface of the elastic envelope can be covered by a polymer and/or gore-tex to provide a smooth surface of the implantable element104.

The inflatable element104can be provided in the inner volume119of the stent103. The inflatable element104may have a substantially cylindrical configuration, wherein an outer diameter of the inflatable element104may be substantially identical to an inner diameter of the stent103. The inflatable element104may enclose a central opening104being parallel to a longitudinal axis of the stent103.

As shown in the cross-sectional views ofFIGS. 3ato3c, the elastic envelope308of the inflatable element104may comprise an outer circumferential portion301which can be attached to the stent103, for example by means of gluing, high temperature gluing or shrink-wrapped polyurethane elements and an inner circumferential portion304enclosing the central opening104. The inner circumferential portion304is connected to the outer circumferential portion301by a first cover portion302and a second cover portion303.

As shown inFIGS. 3ato3c, the fluid supply line105can be attached to the second cover portion303. At least in the inflated state of the inflatable element104, an area350of the second cover portion302adjacent the fluid supply line105may be substantially perpendicular to the longitudinal axis of the stent103, and a portion351of the fluid supply line105adjacent the second cover portion302may be substantially parallel to the longitudinal axis of the stent103. Thus, the fluid supply line105may extend along the aorta201of the patient, wherein the fluid supply line105is bent to a small extent only. In the deflated state of the inflatable element204, the shape of the elastic envelope308may change to a certain extent. The portion351of the fluid supply line105, however, may also extend along the aorta201in the deflated state while being bent only to a small extent.

The inner circumferential portion304of the elastic envelope308may comprise a first portion305adjacent a first end120of the stent103and a second portion306adjacent a second end121of the stent103, wherein the first portion305has a higher degree of elasticity than the second portion306. Due to the higher degree of elasticity of the first portion305of the inner circumferential portion304of the elastic envelope308, the first portion305may be deformed to a greater extent than the second portion306if a pressure difference exists between the inner volume307of the elastic envelope and the exterior of the elastic envelope308.

In some embodiments, the higher degree of elasticity of the first portion305of the inner circumferential portion304of the elastic envelope308may be created by providing the inner circumferential portion304with a smaller thickness adjacent the first end120of the stent103than adjacent the second end121of the stent103. In one embodiment, the thickness of the inner circumferential portion304may increase continuously between the first end120and the second end121of the stent103. In other embodiments, the thickness of the elastic envelope308at the inner circumferential portion304may be substantially equal throughout the first portion305, and may be substantially equal throughout the second portion306, wherein the thickness in the first portion305is smaller than the thickness in the second portion306. In such embodiments, the thickness of the elastic envelope308may increase in a step-like manner at the boundary between the first portion305and the second portion306.

The present invention is not restricted to embodiments wherein the first portion305and the second portion of the inner circumferential portion304of the elastic envelope308have a different thickness. In other embodiments, a higher degree of elasticity may be provided by forming the first portion305and the second portion from different materials. In still further embodiments, the degree of elasticity of the first portion305and the second portion306may be substantially the same.

The cardiac assist device100may further comprise a heartbeat detector106. The heartbeat detector106may be attached to the stent103, for example in the vicinity of the first end120of the stent103. An electrical connection107which may, for example, comprise one or more electrically insulated wires may connect the heartbeat detector106to the extravascular portion102of the cardiac assist device100. The electrical connection107may be used to supply power to the heartbeat detector106and to transmit signals from the heartbeat detector106to the extravascular portion102of the cardiac assist device100.

The heartbeat detector can be configured to detect a cardiac action of the patient wearing the cardiac assist device. In some embodiments, the heartbeat detector106may comprise a flow sensor adapted to detect a flow speed of blood in the vicinity of the heartbeat detector. The flow speed of blood may exhibit periodic variations in time with the heartbeat of the patient. In other embodiments, the heartbeat detector106may comprise a pressure sensor and/or an electrocardiogram sensor detecting pressure variations and variations of an electric potential representative of the patient's heartbeat, respectively. For the purposes of the present invention, any type of flow sensor, pressure sensor and electrocardiogram sensor known to persons skilled in the art may be used. In embodiments of the present invention wherein the heartbeat detector106comprises a pressure sensor, the heartbeat detector106may be configured to detect an arterial and/or venous pressure curve.

The extravascular portion102may comprise a container108configured to protect an interior of the container108from bodily fluids of a patient into whose body the extravascular portion108is implanted. In one embodiment, the container108may comprise a biocompatible material such as, for example, titanium or a plastic material.

The container108may comprise components of a fluid supply adapted to periodically inflate and deflate the inflatable element104by periodically supplying a fluid to the inflatable element104and removing the fluid from the inflatable element104via the fluid line105. Thus, the inflatable element104may periodically expand and contract in time with the supply and removal of the fluid.

The fluid may comprise a gas, for example helium, nitrogen and/or carbon dioxide. In other embodiments, the fluid may comprise a liquid such as water and/or a saline solution. A composition of the fluid may be selected such that a poisoning of the patient may substantially be avoided in case of a leakage of the fluid.

The fluid supply may comprise a pump110connected to the fluid line105. Additionally, the fluid supply may comprise a power supply comprising a battery113, a control unit112adapted to control the operation of the pump110and a fluid reservoir111.

In some embodiments, the pump110may comprise a pneumatic micropump of a type known to persons skilled in the art. The pump110can be adapted to pump the fluid from the fluid reservoir111into the fluid line105connected to the inflatable element104to inflate the inflatable element104, and from the fluid line105back into the fluid reservoir111to deflate the inflatable element104.

The fluid reservoir111can comprise a vessel for storing the fluid. In some embodiments, the vessel can be configured to store the fluid under pressure. In such embodiments, the vessel may be formed from a rigid material such as, for example, a metal to withstand the pressure. In other embodiments, the vessel may be formed from an elastic material such as, for example, silicone, rubber or a plastic material. Thus, the vessel may expand when fluid is pumped into the vessel, and may contract when fluid is pumped out of the vessel. In such embodiments, a pressure obtained in the vessel during the operation of the pump110may be relatively low. Thus, an amount of energy required for the operation of the pump110may be reduced.

The fluid reservoir111can be adapted to store an amount of the fluid being greater than an amount required to completely inflate the inflatable element104. Hence, a fluid reserve may be stored to compensate fluid losses which may be caused by leaks in the cardiac assist device100.

The control unit112may be connected to the pump110, and may further be connected to the heartbeat detector106via the electrical connection107. Thus, the control unit112may receive signals from the heartbeat detector106to adapt the operation of the pump110to the heartbeat of the patient. In particular, the control unit112can be adapted to synchronize the periodic inflation and deflation of the inflatable element104with the cardiac action of the patient, as will be explained in more detail below.

The control unit112can comprise a microcontroller of a type known to persons skilled in the art. Additionally, the control unit112can comprise further electronic components such as switches for opening and closing an electrical connection between the battery113and the pump110. Furthermore, the control unit112can comprise electronic equipment such as a sender and/or receiver for data transmission between the control unit112and a communication device which may be provided outside the patient's body. Thus, a doctor may monitor the operation of the cardiac assist device100while it is implanted into the patient, and/or may configure the cardiac assist device100to better adapt its operation to the specific needs of the patient.

In addition to the battery113, the power supply may comprise an induction coil114. In some embodiments, the induction coil114may comprise a wire formed from an electrically conductive material such as copper and wound into a spiral shape on a plate109. The wire may be covered by an electrically insulating material to avoid electric shortcuts resulting from a contact between the wire and electrically conductive bodily fluids of the patient. The induction coil114can be electrically connected to the battery113which may, in such embodiments, be rechargeable, and/or the control unit.

The induction coil114and the plate109may subcutaneously be implanted into the patient. An electric current in the induction coil114may inductively be generated by providing an external coil outside the body in the vicinity of the induction coil114and applying an alternating current to the external coil. The current may be used to recharge the battery113. In the container108, components such as a transformer and/or a rectifier may be provided to adapt the electrical current for recharging the battery113. Hence, the battery113can be recharged in a convenient manner.

In the following, the implantation of the cardiac assist device will be described with reference toFIGS. 2ato2c.

FIGS. 2ato2cshows schematic view of an aorta201of a patient in stages of a method of implanting the cardiac assist device100. InFIGS. 2ato2c, reference numeral202denotes an aortic valve, reference numerals203,203′ denote the right coronary artery and the left coronary artery, respectively, reference numeral204denotes the innominate artery, reference numeral205denotes the left common carotid artery and reference numeral206denotes the subclavian artery. As persons skilled in the art know, the left ventricle of the patient's heart is located adjacent the aortic valve202and pumps blood into the aorta201.

The endovascular portion101of the cardiac assist device100may be implanted into the ascending part of the aorta201, beginning about 10 to 15 mm above the aortic valve202up to about 5 mm under the offspring of the innominate artery204, as shown schematically inFIG. 2c. Thus, the cardiac assist device100may be used to support the left ventricle of the patients heart. The present invention, however, is not restricted to embodiments wherein the cardiac assist device100is implanted into the aorta201. In other embodiments, the endovascular portion101can be implanted into the pulmonary artery of the patient, beginning about 10 to 15 mm above the pulmonary valve up to about 5 mm under the first off-springing branch of the pulmonary artery to assist the right ventricle of the patient's heart.

To implant the endovascular portion101of the cardiac assist device100, a catheter209may be used. A configuration of the catheter209may be similar to a configuration of heart catheters known to persons skilled in the art. In particular, the configuration of the catheter209may be similar to that of a known catheter adapted for the insertion of an aortic stent adapted for the treatment of an aortic dissection.

The catheter209may run through the central opening118of the inflatable element104, and through the stent103. During the insertion of the endovascular portion101, the stent103can be in the collapsed configuration, and the inflatable element104may be deflated. Hence, during the insertion of the endovascular portion101, the diameter of the endovascular portion103may be relatively small to allow a motion of the endovascular portion through blood vessels of the patient. A sheath207may be provided over the endovascular portion101of the cardiac assist device100. The sheath207may maintain the stent103in the collapsed configuration as long as the stent103is covered by the sheath. Additionally, the sheath207may be marked for x-ray imaging. Moreover, the fluid line105and the electrical connection may run through the sheath207. A nose cone208may be provided at the tip of the catheter209. The nose cone208may have a diameter which is equal to or slightly greater than the inner diameter of the stent103in the collapsed configuration, and may help to avoid a premature sliding of the endovascular portion101off the catheter209.

The catheter209may be inserted into a peripheral artery of the patient by means of the Seldinger technique which is well known to persons skilled in the art. Thereafter, the catheter209can be advanced into the aorta of the patient such that the nose cone208is located in the vicinity of the aortic valve202, as shown inFIG. 2a.

FIG. 2bshows a schematic view of the aorta201in a later stage of the insertion of the endovascular portion101of the cardiac assist device101. After the catheter209has been advanced to the vicinity of the aortic valve202, the sheath207may be withdrawn to expose the endovascular portion101. As the sheath207is removed, portions of the stent103which are not covered by the sheath207any more, may change from the collapsed configuration into the expanded configuration. As already explained above, the outer diameter of the stent103in the expanded configuration may be selected to be equal to or slightly greater than the inner diameter of the patient's aorta201such that the stent103is attached to the aorta201by friction.

The present invention is not restricted to embodiments wherein the stent103is self-expandable such that the stent103changes into the expanded configuration as soon as the sheath207is removed. In other embodiments, the stent103can be adapted such that it may remain in the collapsed configuration after the removal of the sheath207. In such embodiments, the stent103may be expanded by means of a balloon element (not shown) provided in the inner volume119of the stent and attached to the catheter209, which is inflated after the removal of the sheath207. In further embodiments, the stent103may be expanded by inflating the inflatable element104by supplying fluid through the fluid line105.

FIG. 2cshows a schematic view of the aorta201in yet another stage of the insertion of the endovascular portion101of the cardiac assist device101, wherein the sheath207has been completely removed from the stent103. Hence, the stent103is in the expanded configuration and is attached to the aorta201. After removing the sheath207from the stent103, the sheath207may be retracted further to expose the fluid line105and the electrical connection107. Thus, the fluid line105and the electrical connection107may be implanted into blood vessels of the patient. Thereafter, the catheter209may be retracted. If the stent103does not fit exactly to the aorta201, a manual balloon may be used to slightly expand the stent103.

Before or after the insertion of the endovascular portion101of the cardiac assist device100, the extravascular portion102may also be implanted into the patient. This can be done by means of methods of surgery well known to persons skilled in the art. In one embodiment, the container108can be pectorally implanted, and the induction coil114may be implanted at the lateral aspect of the chest. Moreover, the fluid line105and the electrical connection107may be connected to the pump110and the control unit112, respectively. Thereafter, the operation of the cardiac assist device100may be initiated.

In some embodiments, the size of the ascending part of the aorta201may be measured before the insertion of the endovascular portion101, and an appropriate endovascular portion101may be selected on the basis of the measurement. The measurement can be performed by means of techniques known to persons skilled in the art such as x-raying, for example multislice computer tomography and/or three-dimensional computer tomography, wherein, in some embodiments, a contrast agent may be employed.

To insert the endovascular portion101into the subclavian artery206, an incision may be made about 10 to 20 mm below the clavicle near the groove. As an alternative to the Seldinger technique described above, the lower surface of the subclavian artery206may be prepared, and a 6/0 pursestring suture can be made to introduce the endovascular portion101and the catheter209covered by the sheath207via an incision of the subclavian artery206. Using a catheter guide of a type known to persons skilled in the art, the endovascular portion101may then be positioned in the aorta201, as described above.

In embodiments wherein the endovascular portion101is inserted into the pulmonary artery of the patient, the endovascular portion101and the catheter209covered by the sheath207can be inserted into the pulmonary artery via the subclavian vein and the right ventricle of the patient's heart.

In embodiments wherein the stent103is expanded by inflation of the inflatable element104, a balloon dilatation and/or percutaneous coronary intervention may be performed if the stent103is not accurately expanded to fix the endovascular portion101at a desired position.

In further embodiments, the endovascular portion101may be inserted by means of a median sternotomy and a pursestring suture at the distal part of the ascending aorta. The stent103, the inflatable element104and the heartbeat detector106may be inserted through an incision in the aorta. In such embodiments, a catheter and a sheath similar to the catheter209and the sheath207may be used to insert the fluid supply line205and the electrical connection107via a peripheral blood vessel of the patient. The fluid supply line205and the electrical connection107may subsequently be grasped through the incision in the aorta and can then be connected to the inflatable element104and the heartbeat detector106.

To implant the extravascular portion102, a subcutane or subpectoral pocket may be formed in the subclavicular region. For this purpose, techniques similar to those used in the implantation of a pacemaker or implantable cardioverter-defibrillator may be employed, and the container108can be inserted into the pocket.

Additionally, a further subcutane pocket can be formed below the pocket in the subclavicular region at a subaxillar position at the lateral aspect of the thorax and/or in the lateral epigastric region, and the induction coil104and the plate109can be inserted therein.

In the following, the operation of the cardiac assist device will be described with reference toFIGS. 3ato3d.

FIGS. 3ato3dshow schematic cross-sectional views of the ascending part of the aorta201of the patient. The cardiac assist device100is inserted into the aorta201above the right coronary artery203and the left coronary artery203′ and below the innominate artery204(not shown inFIGS. 3ato3d), as described above with reference toFIGS. 2ato2c.

The inflatable element104can be periodically inflated and deflated. The inflation and deflation of the inflatable element104can be synchronized with the cardiac action of the patient, which may be detected by means of the heartbeat detector106. In some embodiments, the inflatable element104can be deflated during systole, and may be inflated during diastole.

FIG. 3ashows a cross-sectional view of the aorta201during systole, immediately after the aortic valve202has opened. At this point of time, the inflatable element104may be substantially completely inflated. Hence, the inflatable element104may occupy a relatively large amount of space in the patient's aorta, and the central opening118of the inflatable element104may have a relatively small diameter. Blood ejected by the left ventricle of the patient's heart may flow through the central opening118, as indicated by arrow320inFIG. 3a.

FIG. 3bshows a cross-sectional view of the aorta201at a later point of time during systole. During the systole, which may be detected by means of the control unit112and the heartbeat detector106, the pump110may be activated to deflate the inflatable element104by pumping fluid out of the inflatable element104. Therefore, the pressure in the inflatable element104and a volume occupied by the inflatable element104in the aorta201can be reduced. Since the outer circumferential portion301of the elastic envelope308is attached to the stent103, the reduction of the volume of the inflatable element104may comprise an increase of the diameter of the central opening118of the inflatable element.

In embodiments of the present invention wherein the first portion305of the inner circumferential portion304of the elastic envelope308comprises a higher degree of elasticity than the second portion306, the decreasing pressure in the inner volume307of the inflatable element104may overcome the stronger mechanical forces exhibited by the less stretchable second portion306to a less extent than the mechanical forces exhibited by the first portion305. Therefore, a diameter of the central opening118may first increase adjacent the second end121of the stent103. Hence, the central opening118may obtain a substantially conical shape. As the deflation of the inflatable element104continues, the diameter of the inflatable element104may also be reduced in the first portion305of the inner circumferential portion304of the elastic envelope308.

Due to the reduction of the volume of the inflatable element104, a vacuum may be created in the aorta201in the vicinity of the heart valve202. Due to this vacuum, blood may be drawn through the aortic valve202into the central opening118of the inflatable element104. Hence, the deflation of the inflatable element may assist the ejection of blood by the patient's ventricle. Thus, an afterload which must be overcome by the ventricle to eject blood may significantly be reduced.

FIG. 3cshows a schematic cross-sectional view of the aorta201and the endovascular portion101of the cardiac assist device100at the end of the systole. At this point of time, the inflatable element104can be in a substantially deflated state such that the inflatable element occupies only a relatively small volume in the aorta201and the central opening118of the inflatable element104is relatively large. The aortic valve202may be substantially completely closed, since the ejection of blood out of the ventricle is substantially completed.

FIG. 3dshows a schematic cross-sectional view of the aorta201and the endovascular portion101of the cardiac assist device100during diastole. At the beginning of the diastole, which may be detected by means of the heartbeat detector106and the control unit112, the control unit112may activate the pump110to pump fluid into the inflatable element104via the fluid line105to inflate the inflatable element104. In some embodiments of the present invention, the inflatable element104may be inflated until a pressure of about 2.67 104Pa (200 mm Hg) is obtained in the inflatable element104. In such embodiments, the pressure in the inflatable element104may be sensed by means of a pressure sensor provided in the inflatable element104and/or in the container108in the vicinity of the pump110.

Due to the inflation of the inflatable element104, a volume occupied by the inflatable element104in the aorta201may increase, and a diameter of the central opening118of the inflatable element104may decrease. Therefore, the inflatable element may push blood which was ejected by the patient's ventricle during systole out of the portion of the aorta201which is occupied by the endovascular portion101of the cardiac assist device100. The aortic valve202of the patient may substantially prevent a flow of blood back into the ventricle. Therefore, a blood flow into the left coronary artery203and the right coronary artery203′, as well as a blood flow through the aorta201in a direction away from the aortic valve202, into the circulatory system of the patient, can be obtained.

In embodiments of the present invention wherein the first portion305of the inner circumferential portion304of the elastic envelope308comprises a higher degree of elasticity than the second portion306, the diameter of the central opening118may first be reduced in the vicinity of the first end120of the stent103, which can be provided adjacent the aortic valve201. As the pressure in the inflatable element104is further increased, the diameter of the central opening118may also increase in the second portion306of the inner circumferential portion304of the elastic envelope308. Thus, a column of blood located in the central opening118of the elastic element104can be pushed upward into the aorta201. This may help to reduce a pressure exhibited on the aortic valve202.

At the end of the diastole, the inflatable element104may be substantially completely inflated, having a configuration similar to that shown inFIG. 3a. During the subsequent systole and diastole, the cycle described above may be repeated.

The amount of blood in the central opening118of the inflatable element104which is pushed into the circulatory system of the patient during diastole may be estimated as
V=2πr2h
wherein r denotes a diameter of the aorta201and h denotes a length of the inflatable element. Since the diameter of a normal aorta may be about 30 mm or more, and the length of the inflatable element104may be about 100 mm, the amount V may be estimated as being about 70.65 ml or more. Hence, with a heart rate varying from about 70 to about 100 beats per minute, about 4900 ml to about 7000 ml may be pumped into the circulatory system of the patent by the cardiac assist device100.

A cardiac output during systole can be influenced by three main factors:1. Preload;2. Afterload; and3. Contractibility.

While the presence of the cardiac assist device100according to the present invention may have a relatively small influence on the preload, the contractibility of the ventricle of the patient's heart may be improved, since blood can be pumped into the right coronary artery203and the left coronary artery203′ during the inflation of the inflatable element104, such that an oxygenation of the myocardium may be improved.

Moreover, as detailed above, the afterload may be significantly reduced by the cardiac assist device according to the present invention, since blood may be sucked out of the ventricle as the inflatable element104is deflated during systole. Hence, the cardiac assist device100according to the present invention may help to increase the cardiac output.

A compromised left ventricle may have a cardiac output of about 2 to about 2.5 l/min or less. Assuming a patient in terminal heart failure with a cardiac output of 1.5 l/min and a heart rate of 80 beats per minute, the cardiac output obtained when using the cardiac assist device100according to the present invention may be estimated as follows:1. An increase of cardiac output during systole to about 2.0 l/min due to the improved contractibility; and2. An additional output of about 5.6 l/min (80 times about 70 ml) provided by the pumping effect of the periodic inflation and deflation of the inflatable element104.

Hence, in a patient whose life might be hard to save even by means of a heart transplant, a total cardiac output of about 7.6 Vmin may be obtained, which may be even slightly more than a normal cardiac output. During activity of the patient, the heart rate might increase to about 120 beats per minute. Hence, a cardiac output of about 11.4Vmin can be obtained, which may be sufficient for a moderate to severe physical activity.

Further embodiments of the present invention will be described with reference toFIG. 4.

FIG. 4shows a schematic cross-sectional view of an endovascular portion401which may be provided in the cardiac assist device100instead of the endovascular portion101described above.

The endovascular portion401comprises a stent403, which may comprise features similar to those of the stent103described above. Similar to the embodiments described above, a heartbeat detector406can be provided at the first end420of the stent403. An electrical connection407may connect the heartbeat detector406to the control unit112.

In an inner volume419of the stent403, an elastic envelope404is provided. The elastic envelope404may comprise an elastic material such as, for example, silicon. The elastic envelope404may comprise a plurality of inflatable elements409,410,411,412,413provided in form of chambers formed in the elastic envelope404which are arranged in a row along a longitudinal direction of the stent403. Hence, a first inflatable element409may be provided adjacent a first end420of the stent403, and a last inflatable element413may be provided adjacent a second end421of the stent403. Between the first inflatable element409and the last inflatable element413, intermediary inflatable elements410-412can be provided. If the endovascular portion401is implanted into a blood vessel of a patient, the first end420of the stent403may be provided adjacent a heart valve of the patient.

A fluid line405can be connected to the pump110, and may be adapted to supply a fluid to the elastic envelope404and to remove fluid from the elastic envelope404for inflation and deflation of the inflatable elements409-413.

An end408of the fluid line405may be provided in the first inflatable element409. Hence, fluid may be pumped into the first inflatable element409and out of the first inflatable element409by operating the pump110. Between each pair of adjacent ones of the inflatable elements409-413, a flow restrictor which may, for example, comprise an orifice, can be provided. Hence, if fluid is pumped into the fluid line405, the fluid may flow from the first inflatable element409into the inflatable element410via flow restrictor414, from the inflatable element410into the inflatable element411via flow restrictor415, from the inflatable element411to the inflatable element412via flow restrictor416, and from the inflatable element412into the last inflatable element413. Hence, the inflatable elements409-413may be inflated successively, since the flow restrictors414-417may slow down fluid flow between the inflatable elements409-413. If fluid is pumped out via the fluid line405, the inflatable elements409-411can be deflated successively, since fluid flow between the inflatable elements409-411can be slowed down by the flow restrictors414-417. Thus, the inflatable elements409-411may be successively inflated and deflated to actively move blood located in a central opening418of the inflatable element404into a desired direction.

The present invention is not restricted to embodiments wherein flow restrictors414-417are provided between adjacent ones of the inflatable elements409-413. In other embodiments, the inflatable elements409-413may be sealed against fluid communication between the inflatable elements409-413, and an individual fluid line may be connected to each of the inflatable elements409-413. Each of the fluid lines may be connected to an individual pump provided in the container108. Hence, each of the inflatable elements409-413may individually be inflated and deflated. This may allow a more precise control of the inflation and deflation of the inflatable elements409-413.

In still further embodiments, a single fluid line may be provided, and a solenoid valve may be provided between the fluid line and each of the inflatable elements409-413. The solenoid valves may be operated by means of an electric current supplied by electrical connections to the control unit112. Hence, the inflatable elements409-413may be inflated and deflated individually by operation of the solenoid valves, whereas the single fluid line may advantageously require a smaller amount of space in the blood vessels of the patient than a plurality of fluid lines.

Moreover, the present invention is nor restricted to embodiments wherein five inflatable elements409-413are provided, as shown inFIG. 4. In other embodiments, a greater or smaller number of inflatable elements409-413can be provided.