Patent Grant
10398822
The present invention relates to a ventricular assist device and, more specifically, to a ventricular assist device suitable for assisting either the left ventricle, the right ventricle, or both ventricles
Left ventricular assist devices are now a therapeutic option in patients with end-stage dilated cardiomyopathy. Existing device are designed for use in severe left ventricular failure. These existing devices have little adaptability for support of the right sided circulation and, in particular, are not well-suited for right ventricular failure. Current device designs also tend to be appropriate for patients with dilated cardiomyopathy, but these devices are not well-suited for use in patients with restrictive cardiomyopathy. Unfortunately, the outcome has been poor for past attempts to existing devices for restrictive cardiomyopathy.
Additionally, further problems with the present generation of devices include the risk of thrombus formation and the risk of infection, as well as negative effects of non-physiologic (non-pulsatile) flow. Non-physiologic flow can potentially cause a number of side-effects, including a high prevalence of gastrointestinal and/or cerebral bleeding. The etiology of the gastrointestinal bleeding is in part related to the non-physiologic flow, and may also be related to the depletion of clotting factors within the blood which may be destroyed by such a non-physiologic assist device. Some existing devices are known to have a 30% incidence of clotting factor depletion.
Current devices also may be difficult to use in the setting of an acute myocardial infarction. In such a situation, the freshly infarcted myocardial tissue may be friable, particularly if the location is apical or anterior. Consequently, use of existing devices may not be feasible because of the apical placement of the inflow cannula.
In accordance with one aspect, a ventricular assist device for a human heart may comprise a stent sized for placement within a cardiac artery and arranged for percutaneous placement at a selected location within the cardiac artery, with the stent arranged to have an open configuration defining a flow path, a rotor sized to fit within the stent and arranged for percutaneous placement at the selected location and within the flow path, with the rotor including a surface disposed about a central portion and angled with respect to the flow path, the rotor further defining a longitudinal axis and having a first plurality of magnets. The device includes a collar sized for placement about the cardiac artery at the selected location, with the collar comprising a stator having an electrical winding. A power source is provided and is operatively coupled to the stator, and the stator and the rotor are arranged to interact in response to the application of power from the power source to the stator to cause the rotor to rotate about the longitudinal axis. A timing control module is provided and is operatively coupled to the stator, and is arranged to control a rotational speed of the rotor. Accordingly, the surface of the rotor is arranged to move blood along the flow path in response to rotation of the rotor.
In accordance with one or more preferred aspects, the collar includes a magnet set and the rotor includes a second plurality of magnets, the magnet set of the collar and the second plurality of magnets of the rotor cooperating to control a longitudinal position of the rotor with respect to the flow path. The selected location can be the aorta, which allows the device to function as a left ventricular assist device, or may be the pulmonary artery, which allows the device to function as a right ventricular assist device. Still further, the device may be placed in both the aorta and the pulmonary artery, which allows the device to function as a bi-ventricular assist device. Preferably, the selected location or locations may be supravalvular. Still further, the collar may be adapted for minimally invasive placement about the appropriate vessel or vessels.
The surface of the rotor may be formed by a plurality of blades, the surface of the rotor may be helical, the surface of the rotor may comprise a plurality of surfaces, and the surface of the rotor may comprise any suitable form or shape to permit movement of blood along the flow path in response to rotation of the rotor.
Preferably, the timing control module is operatively coupled to a sensor arranged to sense native cardiac rhythms, and the timing module is arranged to control the rotational speed of the rotor in response to the native cardiac rhythms. The timing control module may further be arranged to control the rotational speed of the rotor between a baseline speed and a higher speed, wherein the baseline speed is arranged to allow the device to function as a closed valve, and wherein the higher speed is arranged to move blood along the flow path at a desired flow rate.
Still preferably, one or both of the rotor and the stent are coated with an anti-coagulant. The power the power source may be subcutaneous, and may be arranged for transcutaneous charging.
In accordance with another aspect, a ventricular assist device for a human heart may comprise a stent sized for placement within a cardiac artery at a selected location within the cardiac artery and arranged to define a flow path, a magnetized rotor sized to fit within the stent and at the selected location and within the flow path, the rotor including a surface angled with respect to the flow path and including a longitudinal axis, and a collar. The collar is sized for placement about the cardiac artery at the selected location, with the collar comprising a stator having an electrical winding. The device includes a power source operatively coupled to the stator, and the stator and the rotor are arranged to interact in response to the application of power from the power source to the stator to cause the rotor to rotate about the longitudinal axis. A timing control module is provided, and the timing control module is operatively coupled to the stator and is arranged to control a rotational speed of the rotor between a baseline first speed and a higher second speed. The surface of the rotor is arranged to move blood along the flow path in response to rotation of the rotor.
In accordance with a further aspect, a ventricular assist device for a human heart includes a stent, a stator, a rotor, a power source, and a controller. The stent has a cylindrical stent wall with an inner surface defining a flow path and an outer surface configured to be disposed within a blood vessel. The stator is disposable within the stent, the stator having a plurality of support struts connected to the stator and disposable against the inner surface of the stent wall to position the stator within the stent. The rotor includes an outer surface facing the inner surface of the stent wall and defined in part by at least one blade angled with respect to the flow path, the rotor rotatably mounted on the stator between the inner surface of the stent and the stator. One of the rotor and the stator includes a field magnet and the other of the rotor and the stator includes windings. The power source is operatively coupled to the windings, and the controller is operatively coupled to the power source to selectively control the power source to vary the speed of the rotor.
It will be recognized that any of the aspects may be combined with or modified in light of the preferred aspects disclosed herein, as desired.
When assembled in accordance with one or more preferred forms outlined herein, the device may be placed using a minimally invasive, off-pump approach. Epi-aortic magnets may be placed around the ascending aorta or other desired location, while the magnetically suspended (or levitated) rotor or impeller blade is placed in a supravalvular position, above the aortic valve or the pulmonary valve, thus permitting use in either severe left ventricular failure of severe right ventricular failure. Known devices appear unsuitable for placement at one or more of these locations.
By placing the device using a minimally invasive approach in a supravalvular position, the anatomic integrity of the left ventricle or the right ventricle may not be affected, and there is a lower risk of complications related to disruption of the integrity of the ventricular architecture. This may be particularly beneficial in patients experiencing cardiogenic shock following acute myocardial infarction, or experiencing biventricular failure requiring off-pump support to off-load the ventricle(s).
A rotor or impeller blade may be levitated within the stent. Both may be deployed separately and sequentially through the groin using standard techniques with existing methods. The in-stent rotor or impeller may be mounted within the ascending aortic or pulmonary arteries, to support the left or right ventricles respectively. The levitation of the rotor or impeller prevents “touch-down” of the blade or blood driving surface against the wall of the surrounding vessel.
The placement and function of the disclosed device preferably allows the maintenance of pulsatile physiologic flow to augment the natural cardiac cycle of the heart. Preferably, the device achieves phasic blood flow through the use of electrical signals to time the pumping action via the timing control module to augment normal myocardial contractility. Power may be provided by a pacemaker type power unit implanted subcutaneously. In one preferred form, the device uses a transcutaneous charging system. Additionally, near field communication (NFC) technology could be used to impart instructions to the timing control module.
The device may function as an aortic or pulmonary valve. The disclosed device could be considered in place of a mechanical valve in circumstances where there are problems with the native aortic or pulmonary valves when associated with severe cardiac failure of the left or right ventricles respectively. For instance, in severe aortic stenosis with cardiac failure, the native diseased valve could be removed at the time of surgery and the device would—in effect—function as a valve. The same would be true with aortic regurgitation or infective endocarditis. On the right side of circulation, the device could be used in lieu of a pulmonary valve.
The device may assist in the prevention of thrombus or blood clots at the site of device implantation and within the device mechanism with the use of certain techniques. This could be accomplished by the use of systemic anticoagulation or the use of special coatings (e.g. fibrinogen like peptide 2), which prevent formation of thrombus on surfaces of the rotor and stent in contact with the blood. These features and uses are enumerated and discussed in more detail below.
Another aspect of the disclosed device would be the control of power and settings using a near field communication system to control the power requirements and output, the timing, and/or other settings. Such an approach may employ wireless cell phone technology, or other suitable technology, as a means of communication with the control unit. Thus the control system would not need any sort of cable or wired connection, and programming may be accomplished with hand-held devices, such as through a cell phone or other module. The device and its control system would be completely implantable.
Referring now to the drawings,
Referring still to
The device 10 also includes a collar 26 is sized for placement around the selected cardiac artery. As seen in
Referring now to
Referring now to
Referring once again to
As another alternative, the timing control module 34 may be programmed or otherwise arranged to control the rotational speed of the rotor to create a first flow characteristic and a second flow characteristic. For example, the control of the rotor may be such that the first flow characteristic creates at least a partial reverse flow, which would be opposite the direction of the flow path 14. In accordance with at least one exemplary form, such a flow characteristic may act to improve coronary perfusion. The control of the rotor further may be such that the second flow characteristic creates a forward flow, which is along, or otherwise in the direction of, the flow path 14. Preferably, by using the sensor 66, the rotation of the rotor may be gated with the native cardiac rhythms, which allows the device 10 to behave in a manner similar to the behavior of an intra-aortic balloon pump (IABP), with positive forward flow as well as at least some reverse flow.
Referring to
Returning to
The blade or flighting 246 may be collapsible against the outer surface 244 of the rotor 240. In particular, the blade 246 may be collapsible to facilitate delivery to the location of the stent 202. For example, as explained below, the device 200 may include an introducer jacket, and the blade(s) 246 may be collapsed against the rotor 240 (an in particular the outer surface 244) with the jacket disposed about the rotor 240. The blades 246 may extend from the outer surface 244 of the rotor 240 without the jacket disposed about the rotor 240 as is illustrated in
Unlike the embodiments in
According to a first embodiment, the first bearing 260 may be a mechanical pivot. Alternatively, the first bearing 260 may be a hydrodynamic pivot. Further, the first bearing 260 may be a magnetic bearing, such as is described above relative to the embodiments of
Similarly, the second bearing 262 may take on various forms. As illustrated in
As illustrated in
As for the mechanism used to rotate the rotor 240, one of the rotor 240 and the stator 220 includes a field magnet and the other of the rotor 240 and the stator 220 includes coils or windings. As illustrated in
In particular, referring to
The discussion of the device 10 is applicable with equal force to the device 200 as it relates to the operation of the associated power source 280 and controller 282. For example, the controller 282 may be programmed to operate the power source 280 to provide a pulsatile flow. As a further example, the controller 282 may be programmed to control the rotational speed of the rotor 240 between a baseline speed and a higher speed. As a still further example, the device 200 may include a cardiac sensor 288 operatively coupled to the controller 282, the controller 282 being programmed to use the cardiac sensor 288 to determine native cardiac rhythms, and to control the rotational speed of the rotor in response to the native cardiac rhythms.
Other teachings in regard to the power source 32, module 34 and sensor 66 of the device 10 may also be applied to the power source 280, controller 282, and sensor 288 of the device 200. For example, the power source 280 and controller 282 may be arranged for placement subcutaneously. In fact, the power source 280 may be arranged for transcutaneous charging, and the controller 282 may be arranged for transcutaneous programming.
Other teachings applicable to the embodiment of
Having thus described the structure and operation of the devices 10 of
Referring now to
Referring now to
Referring now to
In a similar fashion, the placement of the device 200 is illustrated in
When assembled in accordance with an exemplary aspect of the invention, when the device is used for left ventricular support the device may be placed above the aortic valve and above the origins of the coronary arteries (for example, approximately 1 cm superior to the level of the sino-tubular junction). In such an application, coronary perfusion would not be affected.
The device may be placed through the 2nd right intercostal space through an anterior mini-thoracotomy, off-pump, or through an upper hemi-sternotomy or traditional median sternotomy. Preferably, one or more of the collar, the stent, and the rotor may be collapsible, and thus suitable for minimally invasive placement at the selected location(s). One exemplary a cardiac surgical approach would be a hybrid operating room with the placement of the impeller and stent percutaneously. Following a median sternotomy or upper hemisternotomy, once the aorta has been cross-clamped and the patient placed on cardiopulmonary bypass, the aorta could need to be incised. The decision whether to remove the native aortic valve would be based on its integrity and condition. The device would be mounted above the origins of the coronary arteries. The power source to the unit may be epi-aortic and would be threaded through subcutaneously to the location of the power pack. The device may be mounted on a titanium, or other suitable material, mesh stent-like structure, which would be lightweight and extremely strong. The device mechanism would be mounted within that mesh which would be sized appropriately to fit the aorta. In the case of pulmonary location, this would need to be placed in the supravalvular position in the pulmonary artery.
In another exemplary form, the device (whether the device 10 or the device 200) may be placed using a trans-apical approach as illustrated in
The exemplary device of
Preferably, the timing of the pump function would be optimized to provide phasic flow which would be coordinated with ventricular systole. In many patients with end-stage heart failure, a dual chamber or bi-ventricular pacemaker is often used to create synchronicity in contraction between the atrial and ventricular chambers. Placement of this device would not alter such function. The sensor 68 (or 288) includes electrodes which would be placed on the heart to obtain atrial and ventricular electrograms (the native cardiac rhythms) and this data would be sent to the timing control module 34 (or controller 282). The power source 32 (or 280) preferably is a pacemaker-like power source. The pumping function of the device 10 (or 200) would be timed to coordinate with the ventricular electrical impulse indicating the onset of systole. A pressure sensor may also be provided and preferably would be available to detect changes in pressure thus providing additional information. In this way, the device 10 would be able to adapt to changing needs and changing heart rate conditions. This would result in augmentation of blood flow in a more synchronous fashion. The timing control module 34 would also have algorithms incorporated to take into account the timing of atrial and ventricular signals and input of pressure sensor data to indicate when pressure is rising, thus improving the timing of augmentation of phasic flow. In effect, the pump would increase its flow based on physiologic need. The mechanism is that the baseline speed of the impeller increases, thus forcing blood across the device at higher velocity and augmenting native cardiac function.
Additionally, there are several possibilities to prevent thrombus formation. In one iteration, systemic anticoagulation with traditional anticoagulants in the form of warfarin or low molecular weight heparin could be used with use of low dose aspirin as an anti-platelet agent. In another iteration, the device could be coated with material that prevents formation of thrombus. A non-thrombogenic surface would therefore minimize the need for systemic anticoagulation. In another potential iteration, the use of a direct current charge on the device by coating it with a dielectric and using a specific circuit to distribute the charge could be used (such as that found in PCT Publication No. WO 2008/024714 A1). In another iteration the system could be coated with fibrinogen like peptide that would prevent thrombus formation and prevent the need for systemic anticoagulation.
The unit including the power source 32 and the timing control module 34 (or power source 280 and controller 282) preferably would be positioned as illustrated in
The device as described functions in a synchronous fashion to augment cardiac contractility. Therefore if cardiac standstill occurs, or ventricular arrhythmias occur which prevent normal electrical activation, problems with device function could occur. One iteration of the device includes the use of a defibrillator lead which is attached to the power pack which can be used to sense the presence of ventricular arrhythmias and deliver an appropriate shock to the heart to terminate the arrhythmia. This would be necessary in order to provide continued cardiac output. This could be incorporated into the algorithms which would be programmed into the device. Atrial arrhythmias should not be as much of a problem, provided ventricular rate is maintained.
Because of the supravalvular nature of the device and its lack of interference with native cardiac function, it could be used in different cardiac failure states. In pure left ventricular failure, the valve would be placed in the supra-aortic position. In pure right ventricular failure, it would be placed in the supra-pulmonary valve position. In biventricular failure, two devices could be employed sitting in the aorta and the pulmonary artery with appropriate power packs for each functioning device. The power packs could be placed in a infra-clavicular of infra-diaphragmatic location. In pulmonary hypertension with severe right heart failure, the device could be used in the supra-pulmonary valve position augmenting the function of the failing right ventricle. By virtue of its location, the etiology of the heart failure becomes less important. Thus, it could also be used in diastolic dysfunction and restrictive cardiomyopathic states. By simply augmenting device function and increasing the revolutions per minute during phasic contraction of the heart, the timing of diastolic filling becomes less important.
Because of its location, the device would function adequately as a heart valve in addition to being an assist device. Hence, the native valves could be removed and the ability to stop or slow down the impeller completely would prevent backflow of blood and minimize forward flow of blood during the diastolic phase.
Because of its ability to be located in any major vessel, the device could also be used as a peripheral circulatory assist device for severe peripheral vascular disease. In that iteration, it could be placed in the descending aorta or in the femoral or iliac vessels and thus augment blood flow to the lower limbs. Similarly, it could be placed in other locations within the aorta to augment blood flow in the relevant vascular beds. For instance, in individuals with severe peripheral vascular disease, placement of the device in the infra-renal position would augment natural blood flow and increase perfusion of the lower limbs. In critical lower limb ischemia, improvement of a proximal blood flow may allow the ability to treat the lower limb ischemia.
The disclosed device and/or method may additionally prove especially useful or suitable for placement during congenital heart surgery in patients requiring hypoplastic left heart reconstruction. Those of skill in the art, upon reading the present disclosure, will also find the disclosed device and/or method useful in other procedures as well.
The disclosed device and/or method may also prove especially adaptable for certain energy saving or energy providing technology. For example, the device may be adapted to extract and/or use kinetic energy from the heart and/or from the flow of blood, and use that energy to supply at least a portion of the power requirements of the device. Further, the device may be especially suitable for use with bionic fuel cell power, which can extract electrons from blood glucose, thus supplying power to the device. A more detailed explanation of such bionic fuel cell technology can be found in Microfabricated Miniature Biofuel Cells with Nanoengineered Enzyme Electrodes, by Nishizawa et al. and Miniaturized Microfluidic Biofuel Cells, by Nishizawa.
Preferred embodiments of this invention are described herein, including the best mode or modes known to the inventors for carrying out the invention. Although numerous examples are shown and described herein, those of skill in the art will readily understand that details of the various embodiments need not be mutually exclusive. Instead, those of skill in the art upon reading the teachings herein should be able to combine one or more features of one embodiment with one or more features of the remaining embodiments. Further, it also should be understood that the illustrated embodiments are exemplary only, and should not be taken as limiting the scope of the invention. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the aspects of the exemplary embodiment or embodiments of the invention, and do not pose a limitation on the scope of the invention. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
This application is a continuation of U.S. patent application Ser. No. 13/686,885, filed Nov. 27, 2012, which claims the benefit of U.S. Application No. 61/564,264, filed Nov. 28, 2011, and U.S. Application No. 61/566,489, filed on Dec. 2, 2011, all of which are hereby incorporated by reference in their entirety herein.
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| Child | 15007005 | US |
