HK40007512B - Implantable pump system having an undulating membrane - Google Patents

Description

Implantable pump system with undulating membrane

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the filing date of united states provisional patent application No. 62/321,076, filed 2016, 4, 11, the disclosure of which is incorporated herein by reference.

Technical Field

The present invention relates generally to cardiac pumps, and more particularly to implantable pumps having a pulsatile membrane designed to reduce hemolysis and platelet activation.

Background

The human heart includes four main chambers: two ventricles and two atria. Generally, the right heart receives deoxygenated blood from the body into the right atrium and pumps it to the lungs via the right ventricle. The left heart receives oxygen-enriched blood from the lungs into the left atrium and pumps it through the left ventricle to the aorta for distribution throughout the body. Due to any of several diseases including coronary artery disease, hypertension, valve regurgitation and calcification, damage to the heart muscle caused by infarction or ischemia, myocarditis, congenital heart defects, abnormal heart rhythm, or various infectious diseases, the left ventricle can be rendered less efficient and therefore unable to pump oxygenated blood throughout the body.

The united states centers for disease control and prevention (CDC) estimates that about 510 million people in the united states suffer from some form of heart failure. Heart failure is generally classified into four distinct stages, the most severe of which is end-stage heart failure. In the case where a patient has heart failure symptoms at rest despite treatment, end-stage heart failure can be diagnosed. Patients at this stage may have systolic heart failure, which is characterized by a reduced ejection fraction. In patients with systolic heart failure, the ventricular wall (which is usually thick in healthy patients) becomes thin and fragile. Thus, during systole, a reduced volume of oxygenated blood is injected into the blood circulation, which continues in a spiral descending manner until death. One year mortality in patients diagnosed with end-stage heart failure is approximately 50%.

For patients who have reached end-stage heart failure, treatment regimens are limited. In addition to continuing with the medications commonly prescribed during early heart failure, typical recommendations are heart transplantation and implantation of mechanical aids. While heart transplantation can significantly extend the life of a patient to reduce annual mortality, patients often wait on a waiting list for a suitable donor heart for months and sometimes years to die. Currently, the only alternative to heart transplantation is mechanical implantation. While mechanical implants have improved designs in recent years, these implants typically extend the life of the patient by only a few years at most and include several comorbidities.

One type of mechanical implant commonly used in patients with end-stage heart failure is the Left Ventricular Assist Device (LVAD). LVAD is a surgically implanted pump that draws oxygenated blood from the left ventricle and pumps it directly to the aorta, thereby relieving (reducing) the pumping work of the left ventricle. LVAD is commonly used as "transition therapy prior to transplantation" or "replacement therapy". When used for transition therapy prior to transplantation, LVAD is used to extend the life of patients awaiting heart transplantation. LVAD may be used as an alternative therapy to extend life or improve the quality of life of patients when they are not suitable for heart transplantation, but such extension can last only a few years.

Generally, the LVAD includes an inlet cannula, a pump, and an outlet cannula, and is coupled to an extracorporeal battery and a control unit. The inlet cannula is typically connected directly to the left ventricle (e.g., at the apex) and delivers blood from the left ventricle to the pump. The outlet cannula is typically connected to the aorta distal to the aortic valve, delivering blood from the pump to the aorta. Typically, a hose-type structure (e.g., a dacron vascular prosthesis) is used to extend the outlet cannula of the pump to reach the proper delivery location on the aorta. Early LVAD designs were of the reciprocating type but recently rotating and centrifugal pumps have been used.

U.S. patent No. 4,277,706 entitled "Actuator for Heart Pump" (Isaacson) describes a LVAD with a reciprocating Pump. The pump described in the Isaacson patent includes: a housing having an inlet and an outlet; a cavity inside the pump connected to the inlet and the outlet; a flexible membrane extending across the cavity; a plate secured to the membrane; and a ball screw configured to reciprocate to drive the plate and connect the membrane from one end of the cavity to the other end to simulate systole and diastole. The ball screw is actuated by a dc motor. The Isaacson patent also describes a controller configured to manage the rotation of the ball screw to control start, stop and reverse direction to control blood flow into and out of the pump.

Previously known reciprocating pumps LVAD have several disadvantages. These pumps are typically bulky, heavy and may require removal of bone and tissue within the thoracic cavity for implantation. They also require a large amount of energy to expel the blood through the compression chamber. Moreover, the pump subjects the blood to significant pressure fluctuations as it passes through the pump, resulting in high shear and risk of hemolysis. These pressure fluctuations may be exaggerated at higher blood flow rates. Furthermore, depending on the geometry of the pump, areas with little or no flow may cause flow stagnation, which may lead to thrombosis and possibly fatal medical conditions (e.g., stroke). Finally, positive displacement pumps as described in the assackson patent cannot achieve pulsatility similar to the natural heart (e.g., about 60 to 100 times per minute) while maintaining a physiological pressure gradient.

LVADs using both rotary and centrifugal configurations are also known. For example, U.S. patent No. 3,608,088 entitled "Implantable Blood Pump" to Reich (Reich) describes a centrifugal Pump to assist in failing hearts. The reishi patent describes a centrifugal pump having an inlet connected to a rigid cannula coupled to the left ventricular chamber and a dacron vascular prosthesis extending from the pump diffuser to the aorta. The pump includes an impeller that rotates at high speed to accelerate blood and simulates the pulsation of the natural heart by changing the rotational speed or introducing a fluidic oscillator.

United states patent No. 5,370,509 to Golding (gold) entitled "Sealless Rotodynamic Pump with Fluid Bearing" describes an axial blood Pump that can be used as a cardiac Pump. One embodiment described relates to an axial flow blood pump having impeller blades aligned with the axis of the blood inlet and blood outlet. U.S. patent No. 5,588,812 to Taylor (Taylor) entitled "Implantable Electrical Axial-Flow Blood Pump" describes an Axial-Flow Blood Pump similar to the gordin patent. The pump described in the taylor patent has: a pump housing defining a cylindrical blood conduit through which blood is pumped from an inlet to an outlet; and a rotor blade rotating along the shaft of the pump to accelerate the flow of blood through the blood conduit.

While previously known LVAD devices have been improved, these pump designs are not without problems. Like reciprocating pumps, rotary and centrifugal pumps are typically bulky and difficult to implant. While a rotary pump is mechanically distinct from a positive displacement pump, it also exhibits undesirable characteristics. Like positive displacement pumps, rotary pumps apply significant shear to the blood, thereby creating the risk of hemolysis and platelet activation. The nature of the disc or blade rotating about the shaft results in regions of high and low speed as well as vibration and heat generation. In particular, the region near the edge of the disk or blade furthest from the axis of rotation experiences a higher angular velocity and hence flow velocity than the region closest to the axis of rotation. The resulting radial velocity profile along the rotating blades results in high shear being applied to the blood. In addition, stagnation or low flow velocities near the axis of rotation can lead to thrombus formation.

While centrifugal pumps are capable of producing pulsating flow by varying the rotational speed of the associated disks or blades, this only exacerbates the problems caused by steep radial velocity profiles and high shear. In common practice, the output of currently available rotary pumps (measured as flow rate at a given head) is controlled by varying the rotational speed of the pump. The change in rotational speed cannot be instantaneous but instead must be gradual, taking into account the mass of the rotating parts, the angular velocity of the rotating parts and the resulting inertia. Thus, while centrifugal pumps can mimic pulsatile flow with gradual speed changes, the resulting pulse is not immediate and differs from a typical physiological pulse.

Moreover, rotary pumps often result in the application of non-physiological pressure to the blood. This high operating pressure has the adverse effect of over-dilating the vessel, which in the presence of continuous flow can cause the vessel to fibrillate and become inelastic. This in turn can lead to loss of elasticity in the circulatory system, promoting calcification and plaque formation. Furthermore, if the rotational speed of the pump is changed to simulate pulsating flow or increase the flow rate, the rotary pump is less likely to operate at its optimal operating point, reducing efficiency and increasing energy losses and heat generation.

LVADs may also be configured to increase blood flow to match the needs of the patient. Numerous publications and patents describe methods for adjusting LVAD pump flow to match the flow requested by the patient. For example, U.S. patent No. 7,520,850 entitled "Feedback control and ventricular assist devices" to Brockway describes a system and method for controlling a ventricular assist device using pressure Feedback. The system described in the brevich patent attempts to maintain a constant filling of the ventricles by measuring the ventricular pressure and/or ventricular volume. While such systems can achieve flow rates of up to 8 or 9 liters per minute, these flow rates are typically outside the effective operating range of current rotary pumps, which are typically tuned to operate in the range of 4 to 6 liters per minute. Thus, increasing the flow rate in a rotary pump to match patient demand results in non-optimal pump performance.

Pumps for discharging fluid other than rotary and positive displacement types are known in the art. For example, united states patents No. 6,361,284 and No. 6,659,740 entitled "Vibrating Membrane Fluid Circulator" of derevir (Drevet) describe pumps in which a deformable Membrane vibrates to propel Fluid through a pump housing. In these patents, the vibratory motion applied to the deformable membrane results in wave-like fluctuations in the membrane that propel fluid along a channel. Different flow rates can be achieved by controlling the stimulus applied to the membrane.

United states patent number 7,323,961 entitled "Electromagnetic Machine with a Deformable Membrane" to derevir (Drevet) describes a device in which the Membrane is coupled in tension along an outer edge to an Electromagnetic device arranged to rotate around the Membrane. As the electromagnetic device rotates, the outer edge of the membrane is slightly deflected in a direction perpendicular to the plane of the membrane. These deflections cause wave-like fluctuations in the membrane that can be used to move the fluid in contact with the membrane.

United states patent No. 9,080,564 entitled "Diaphragm Circulator" to derevir (Drevet) describes a tensioned deformable membrane in which undulations are created by electromagnetically moving a magnetized ring attached to the outer edge of the deformable membrane over a coil. Axial displacement of the magnetized ring causes fluctuation of the film. As in the' 961 patent, membrane fluctuations may be controlled by manipulating the magnetic attraction. United states patent No. 8,714,944 entitled "Diaphragm Pump with corrugated Diaphragm having Improved Efficiency (diepsagm Pump with a Crinkle diepsagm of Improved Efficiency)" of derlervir (Drevet) and united states patent No. 8,834,136 entitled "corrugated Diaphragm Pump" of derlervir (Drevet) teach similar types of Diaphragm pumps.

None of the aforementioned patents to dellervir describe a diaphragm pump suitable for use in a biological environment or capable of pumping blood for extended periods of time with a low risk of flow stagnation leading to thrombosis.

There is a need for an energy efficient operable implantable pump that is lightweight, small in size, and quick to start and stop in response, with minimal blood damage over a large range of flow rates.

Disclosure of Invention

The present invention overcomes the shortcomings of previously known LVAD systems and methods by providing an implantable pump system having a fluctuating membrane capable of generating a wide range of physiological flow rates while applying low shear to the blood, thereby reducing hemolysis and platelet activation relative to previously known systems.

According to one aspect of the invention, the implantable blood pump system includes an implantable pump, a controller, and a rechargeable battery, each electrically coupled to one another. The system further may include a programmer in communication with the controller to set and change pumping parameters.

An implantable blood pump constructed in accordance with the principles of the present invention may have: an implantable housing configured to be implanted at a heart of a patient; a membrane disposed within the implantable housing; and an actuator system also disposed within the implantable housing, the actuator system having a stationary component and a moving component. The moving component may be coupled to the membrane. The actuator system may receive an electrical signal to cause the moving component to reciprocate at different frequencies and amplitudes relative to the stationary component, thereby causing the membrane to reciprocate at different frequencies and amplitudes, resulting in blood flow.

The implantable housing may include an inlet and an outlet. The membrane may be part of a membrane assembly disposed concentrically within the housing proximal to the outlet. The membrane may be a tensioned flexible circular membrane having a central aperture. The tensioned flexible membrane may be coupled to a rigid ring. The stationary portion of the actuator system may include a stator assembly and an electromagnet assembly and the moving component may be a magnetic ring. The electromagnet assembly selectively generates a magnetic field. The magnetic ring may be coupled to the rigid ring and may be suspended concentrically about the brake. The magnetic ring is reciprocable in response to the magnetic field generated by the electromagnet assembly. During operation of an implantable blood pump, blood may enter the inlet, flow around the actuator assembly and the magnetic ring, flow through the membrane, and eventually flow out of the outlet.

The magnetic ring may be coupled to the membrane assembly and first and second suspension rings by three rigid posts equally spaced around the actuator assembly, such that the first and second suspension rings allow the magnetic ring to reciprocate over the actuator assembly but resist movement in other directions. The first and second suspension rings act as springs that enable movement of the magnetic ring over the actuator assembly. The implantable blood pump can further include a housing securing ring positioned concentrically around the actuator assembly and coupled to both the actuator assembly and the housing, which anchors the actuator assembly to the housing.

In accordance with the principles of the present invention, the magnetic ring is configured to cause an undulating deformation in the circular membrane by reciprocating over the actuator assembly in response to alternating energization of first and second electromagnetic coils. This reciprocation causes a wave-like deformation in the circular membrane having a magnitude determined by the displacement and frequency of the magnetic ring movement. The undulating deformation of the circular membrane in turn causes a flow through the pump, enabling a physiological flow rate in the range between 4 and 10 litres per second.

According to another aspect of the present principles, the controller may be programmed to vary the actuation of the actuator assembly to cause the pump to generate a pulsating flow. Methods for pumping blood from the left ventricle to the aorta using the implantable blood pump and system of the present invention are also provided.

Drawings

Fig. 1 depicts an exemplary embodiment of a pump system of the present invention comprising an implantable pump, a controller, a battery, a programmer, and a mobile device.

Fig. 2 is a perspective view of the implantable pump of fig. 1.

Fig. 3A and 3B are perspective and schematic views, respectively, of the electronic components of an exemplary embodiment of a controller of the present invention.

Fig. 4 is a plan view of an extracorporeal battery used in the pump system of the present invention.

Fig. 5A and 5B are perspective and schematic views, respectively, of the electronic components of an exemplary embodiment of a programmer of the present invention.

Figure 6 is a perspective view of the pump assembly of the present invention.

Fig. 7 is a perspective cross-sectional view of an implantable pump of the present invention.

Fig. 8 is an exploded view of the implantable pump of the present invention.

Figure 9 is a perspective cross-sectional view of the pump assembly of the present invention.

FIG. 10 is a perspective cross-sectional view of the membrane assembly of the present invention.

Figure 11 is a perspective cross-sectional view of the moving component of the pump assembly according to the first embodiment of the present invention.

Fig. 12 is a cross-sectional view of an implantable pump of the present invention.

Fig. 13 is a cross-sectional view of a lower portion of an implantable pump depicting the flow channel and membrane assembly in a resting position.

Fig. 14 is a cross-sectional view of the lower portion of an implantable pump depicting the flow channel and membrane assembly as the membrane undulates.

Detailed Description

The implantable pump system of the present invention is particularly well suited for use as a Left Ventricular Assist Device (LVAD) and comprises a pulsatile membrane pump suitable for long-term implantation into patients with end-stage heart failure. An implantable pump system constructed in accordance with the principles of the present invention includes an implantable pump and an extracorporeal battery, a controller and a programmer. An implantable pump includes a housing having an inlet and an outlet, a flexible membrane, and an actuator assembly. When configured as a LVAD, the housing comprises an inlet cannula inserted into the left ventricle of the patient near the apex of the heart and an outlet cannula surgically placed in fluid communication with the aorta of the patient. By activating an actuator assembly within the implantable pump, membrane fluctuations are induced, thereby causing blood to be drawn into the pump through the inlet cannula and expelled into the aorta through the outlet cannula. The flow rate and pulsatility can be manipulated by changing one or more of the frequency, amplitude, and duty cycle of the actuator assembly.

Referring now to FIG. 1, a pump system 10 constructed in accordance with the principles of the present invention is described. Pump system 10 includes an implantable pump 20, a controller 30, a battery 40, a programmer 50, and a software module optionally programmed to run on a mobile device 60. The implantable pump 20 is configured to be implanted within the chest cavity of a patient such that the inlet cannula 21 is coupled to the left ventricle LV of the heart H. The outlet cannula 22 of the pump 20 is configured to be coupled to the aorta a. The inlet cannula 21 is preferably coupled to the apex of the left ventricle LV, while the outlet cannula 22 is coupled to the aorta a near the ascending aorta, above the level of the cardiac arteries. The implantable pump 20 can be attached within the patient's chest using a circumferential suture or other conventional techniques. An outlet cannula 22 (which may comprise a dacron graft or other synthetic material) is coupled to an outlet 23 of the implantable pump 20.

Referring now also to fig. 2, in a preferred embodiment, implantable pump 20 is comprised of an upper housing portion 24 and a lower housing portion 25 joined to the lower housing portion along an interface 26, such as by threading or welding, to form a fluid-tight pump housing 27 that may have a cylindrical shape. The upper housing portion 24 includes an inlet cannula 21 and an electrical conduit 28 for receiving electrical wires from the controller 30 and the battery 40. The lower housing portion 25 includes an outlet 23 coupled to an outlet cannula 22, as shown in fig. 1. The pump housing 27 is made of a biocompatible material (e.g., stainless steel) and is sized for implantation within the patient's chest cavity.

Referring again to fig. 1, in one embodiment, the controller 30 and battery 40 are external and sized to be placed on a belt or clothing worn by the patient. Both the controller 30 and the battery 40 are electrically coupled to the implantable pump 20, such as via a cable 29 extending through a percutaneous opening in the patient's skin and into an electrical conduit 28 of the pump housing 27. Illustratively, the battery 40 is electrically coupled to the controller 30 via a cable 41 integrated into a belt 42. In an alternative embodiment, the controller 30 may be enclosed within a biocompatible housing and sized for subcutaneous implantation into the abdominal cavity of a patient. In this alternative embodiment, the controller 30 may include a wireless transceiver for bidirectional communication with an extracorporeal programming device and also include a battery that is continuously and inductively charged via the extracorporeal battery 40 and extracorporeal charging circuitry. As will be appreciated, the foregoing alternative embodiment avoids the use of a percutaneous cable 29, and thus eliminates a frequent source of infection for conventional LVAD devices.

Battery 40 preferably comprises a rechargeable battery capable of charging implantable pump 20 and controller 30 for several days (e.g., 3 to 5 days) before recharging is required. The battery 40 may include a separate charging circuit (not shown) as is common with rechargeable batteries. The battery 40 is preferably disposed within a housing adapted to be carried on a belt or holster so as not to interfere with the patient's daily activities.

Programmer 50 may be comprised of a conventional laptop computer programmed to execute programming software routines for use by a clinician or medical professional in configuring and providing operating parameters to controller 30. The configuration and operating parameter data is stored in a memory associated with the controller 30 and used by the controller to control the operation of the implantable pump 20. As described in further detail below, controller 30 directs implantable pump 20 to operate at specific parameters determined by programmer 50. Programmer 50 is preferably coupled to controller 30 via cable 51 only when operating parameters of the implantable pump are initially set or periodically adjusted (e.g., when the patient is visiting a clinician).

According to another aspect of the present disclosure, mobile device 60, which may be a conventional smartphone, may include applications for bi-directional and wireless communication with controller 30, such as via WiFi or bluetooth communication. The application on the mobile device 60 may be programmed to allow the patient to send instructions to the controller to modify or adjust a limited number of operating parameters of the implantable pump 20 stored in the controller 30. Alternatively or additionally, the mobile device 60 may be programmed to receive data from the controller 30 and display data regarding the operation of the implantable pump 20 or an alarm or status message generated by the controller 30 on a screen 61 of the mobile device 60.

With respect to fig. 3A and 3B, the controller 30 is described in more detail. As depicted in fig. 1, the controller 30 may be sized and configured to be worn on the exterior of the patient's body and may be incorporated into a garment (e.g., a belt or vest). The controller 30 includes an input port 31, a battery port 32, an output port 33, an indicator light 34, a display 35, a status light 36, and a button 37.

Input port 31 is configured to periodically and removably accept a cable 51 to establish an electrical connection between programmer 50 and controller 30 via, for example, a USB connection. In this manner, a clinician may be coupled to the controller 30 to set or adjust operating parameters stored in the controller 30 for controlling the operation of the implantable pump. Additionally, when programmer 50 is coupled to controller 30, the clinician may also download data from controller 30 regarding the operation of the implantable pump (e.g., actuation statistics) for processing and presentation on display 55 of programmer 50. Alternatively or additionally, controller 30 may include a wireless transceiver for wirelessly communicating with programmer 50 regarding such information. In this alternative embodiment, wireless communications between the controller 30 and the programmer 50 may be encrypted with an encryption key associated with the unique identification number (e.g., serial number) of the controller.

The battery port 32 is configured to removably accept a cable 41 (illustratively shown in fig. 1 as being integrated with the strap 42) such that the cable 41 is routed through the strap and extends around the patient's back until it is coupled to the controller 30. In this manner, the battery 40 may be removed from the belt 42 and disconnected from the controller 30 to enable the patient to periodically replace the battery with a fully charged battery. It is contemplated that the patient will have at least two batteries available to him or her so that while one battery is coupled to the controller 30 to power the controller and implantable pump, the other battery may be connected to a recharging station. Alternatively or additionally, the battery port 32 may be configured to accept a cable that is directly coupled to a power source, this generally larger battery/charger combination allowing the patient to remove the battery 40 while lying supine in bed (e.g., sleeping).

The output port 33 is electrically coupled to the cable 29, which cable 29 is in turn coupled to the implantable pump 20 through the electrical conduit 28 of the pump housing 27. The cable 29 provides both energy to power the implantable pump 20 and to receive data from sensors disposed in the implantable pump 20 according to configuration settings and operating parameters stored in the controller 30. In one embodiment, the cable 29 may comprise a cable with a biocompatible coating and is designed to extend percutaneously. The cable 29 may be impregnated with a medicament to reduce the risk of infection, the transmission of potentially hazardous substances, or to promote healing where it extends through the patient's skin.

As mentioned above, the controller 30 may include an indicator light 34, a display 35, a status light 36, and a button 37. Indicator light 34 may visually display information related to the operation of the system, such as the remaining life of battery 40. The display 35 may be a digital liquid crystal display that displays real-time pump performance data, patient physiological data (e.g., heart rate), or operating parameters of the implantable pump (e.g., target pump pressure or flow rate), among others. When certain parameter conditions are determined to exceed preprogrammed thresholds, an alarm may be issued and may be displayed on display 35. The status light 36 may include Light Emitting Diodes (LEDs) that turn on or off to indicate whether certain functionality of the controller or implantable pump is functional. The button 37 may be used to wake up the display 35 to set or subside alarms, etc.

With respect to FIG. 3B, the components of an illustrative embodiment of the controller 30 of FIG. 3A are described. In addition to the components of the controller 30 described in connection with fig. 3A, the controller 30 further includes a microprocessor 38, a memory 39, a battery 43, an optional transceiver 44, and an amplifier circuit 45. The microprocessor may be a general purpose microprocessor in which programming for controlling the operation of implantable pump 20 is stored in memory 39. Memory 39 may also store configuration settings and operating parameters of implantable pump 20. Upon periodic swapping out of the battery 40, the battery 40 supplies power to the controller 30 to provide operational continuity. Optional transceiver 44 facilitates the communication viaBy any of several well-known communication standards, including BLUETOOTH^TMZigBee, and/or any IEEE 802.11 wireless standard (e.g., Wi-Fi or Wi-Fi direct)) wirelessly communicate with programmer 50 and/or mobile device 60. Controller 30 further may include amplifier circuitry 45 for amplifying electrical signals communicated between controller 30 and implantable pump 20.

Referring now to fig. 4, a battery 40 is depicted. The battery 40 provides power to the implantable pump 20 and may also provide power to the controller 30. The battery 40 may be comprised of a single battery or a plurality of batteries disposed within a housing, and is preferably sized and configured to be worn on the exterior of the patient's body (e.g., on the belt 42). A battery life indicator 46 may be provided on the exterior of the battery 40 to indicate the degree of charge remaining in the battery. A cable 41 may have one end removably coupled to the battery 40 and the other end removably coupled to a battery port of the controller 30 to supply power to power the implantable pump 20. In one embodiment, the battery 40 may be recharged using a separate charging station, as is known in the art of rechargeable batteries. Alternatively or additionally, the battery 40 may include a port 47 that is removably coupled to a transformer and cable to allow the battery to be recharged using a conventional household power outlet (e.g., 120V, 60Hz AC power supply).

Referring now to fig. 5A through 5B, programmer 50 is described. Programmer 50 may be a conventional laptop computer loaded with programming software routines for configuring controller 30 and setting operating parameters used by controller 30 to control the operation of implantable pump 20. As discussed above, programmer 50 is typically located within the clinician's office or hospital and is coupled to controller 30 via cable 51 or wirelessly to first set up controller 30 and then periodically adjust operating parameters as may be needed thereafter. The operating parameters of controller 30 set using the programming routines of programmer 50 may include, but are not limited to, applied voltage, pump frequency, pump amplitude, target flow rate, pulsatility, and the like. When initially implanted, the surgeon or clinician may use programmer 50 to communicate initial operating parameters to controller 30. After implantation, the patient may periodically return to the clinician's office to adjust the operating parameters, which may again be done using programmer 50.

Programmer 50 may be any type of conventional personal computer device, such as a laptop computer or a tablet computer with touch screen capabilities. As illustrated in fig. 5B, programmer 50 preferably includes a processor 52, memory 53, input/output devices 54, a display 55, a battery 56, and a communication unit 57. The memory 53 may contain an operating system for the programmer and programming routines needed to communicate with the controller 30. Communication unit 57 may include any of a number of well-known communication protocols, such as BLUETOOTH^TMZigBee, and/or any IEEE 802.11 wireless standard (e.g., Wi-Fi or Wi-Fi direct). As illustrated in fig. 5A, the programming routine used for programming and in communication with controller 30 may also provide data identifying the operating parameters used by controller 30 to control implantable pump 20 for display on the screen of programmer 50. The programming routine may also enable the programmer 50 to download operating or physiological data from the controller 30 that is passed by the implantable pump and display that information in real time as the programmer is coupled to the controller via a wired or wireless connection. The transferred data may then be processed and displayed on the screen of programmer 50.

Referring now to fig. 6 and 7, a preferred embodiment of the pump assembly 70 and implantable pump 20 is illustrated. However, it should be understood that the pump assembly and implantable pump, and the components included therein, may have shapes and sizes different than illustrated in fig. 6 and 7 without departing from the invention described herein. As illustrated in fig. 7, the pump assembly 70 is configured to fit within the pump housing 27. To secure the pump assembly 70 within the pump housing 27, the pump assembly 70 may include a securing ring 71 that may extend from and around the stator assembly 72 and may be captured between the upper and lower housing portions 24, 25 when the housing portions are assembled, as illustrated in fig. 7. In this manner, stator assembly 72 may be suspended within the pump housing to be in a close fitting relationship with the inner wall of the pump housing. The stationary ring 71 is preferably a rigid annular structure disposed concentrically around the stator assembly 72 and having a diameter greater than the stator assembly 72. The fixed ring 71 may be rigidly coupled to the stator assembly 72 via struts 73. Struts 73 may create a gap 74 between fixed ring 71 and stator assembly 72, which is preferably about 0.05mm at its most constrained point.

As shown in fig. 7, the pump assembly 70 may be disposed in the pump housing 27 such that the securing ring 71 is captured on a step 75 formed between the upper housing portion 24 and the lower housing portion 25. In this manner, stator assembly 72 may be suspended within pump housing 27 and prevented from moving within the pump housing. Pump housing 27 is preferably sized and configured to conform to pump assembly 70 such that stator assembly 72 does not contact the interior of the pump housing at any location other than at fixed ring 71.

Fig. 8 is an exploded view of the implantable pump 20 depicting the arrangement of internal components of the pump assembly 70 arranged between the upper and lower housing portions 24, 25. In particular, the pump assembly 70 can include a stator assembly 72, a magnetic ring assembly 76, a first electromagnetic coil 77, a second electromagnetic coil 78, a fixed ring 71, a first suspension ring 79, a second suspension ring 80, a post 81, and a membrane assembly 82. The stator assembly 72 may include a tapered section 83, electromagnetic coil retainer portions 84, 85, and 86, and a flange portion 87. Magnetic ring assembly 76 may include a magnetic ring 88 and magnetic ring holder portions 89 and 90. The first and second electromagnetic coils 77 and 78, along with the electromagnetic coil holder portions 84, 85, and 86, may form an electromagnet assembly 91. The electromagnet assembly 91 together with the stator assembly 72 form an actuator assembly. The actuator assembly, along with magnetic ring assembly 76, in turn, forms an actuator system for implantable pump 20.

The first and second electromagnetic coils 77, 78 may be concentrically sandwiched between the electromagnetic coil holder portions 84, 85, and 86 to form an electromagnet assembly 91. The tapered section 83 (which may be coupled to the fixed ring 71 and the first suspension spring 79) may be concentrically positioned atop the electromagnet assembly 91. The magnetic ring 88 may be disposed with magnetic ring holder portions 89 and 90 to form a magnetic ring assembly 76, which may be disposed concentrically to reciprocate over an electromagnet assembly 91. The second suspension ring 80 may be disposed concentrically below the electromagnet assembly 91. The flange portion 87 may be disposed concentrically below the second suspension ring 80. The posts 81 may engage the first suspension ring 79, the magnetic ring assembly 76 and the second suspension ring 80 at equally spaced locations around the actuator assembly. The membrane assembly 82 may be positioned concentrically under the flange portion 87 and engaged with the post 81.

Further details of the pump assembly 70 are provided with respect to fig. 9. In particular, the actuator assembly 95 includes the stator assembly 72 and the electromagnet assembly 91 (including the first and second electromagnetic coils 77 and 78). During use of implantable pump 20, actuator assembly 95 remains stationary relative to pump housing 27. The first and second electromagnetic coils 77, 78 may be separated by an electromagnetic holder portion 85. Controller 30 and battery 40 are electrically coupled to electromagnetic coils 77 and 78 via electrical cable 29 extending through electrical conduit 28 of pump housing 27 to supply electrical current to electromagnetic coils 77 and 78. The first and second electromagnetic coils 77, 78 may be in electrical communication with each other or may be configured to operate separately and have separate wired connections to the controller 30 and the battery 40 via the cable 29.

Electromagnetic coils 77 and 78 may be made of any electrically conductive metallic material (e.g., copper) and further may include one or more smaller metallic wires wound into a coil. The wire of the electromagnetic coil is insulated to prevent shorting to adjacent conductive material. Other components of the pump assembly 70, such as the stator assembly 72, are preferably also insulated and/or made of non-conductive materials to reduce undesired transmission of electrical signals.

The actuator assembly 95 may be surrounded by the first and second suspension rings 79, 80. The suspension rings 79 and 80 may have an annular shape and fit concentrically around the actuator assembly 95. The first suspension ring 79 is preferably rigidly affixed to a tapered section 83 near the top of the stator assembly 72 via struts 73 extending from the suspension ring to the stator assembly. As discussed above, the struts 73 may also attach the fixed ring 71 to the stator assembly 72. The fixed ring 71 and the first suspension spring 79 may be sized and positioned such that there is a gap of no less than 0.5mm between the first suspension ring 79 and the fixed ring 71. The second suspension ring 80 may similarly be affixed via struts to near the bottom of the stator assembly 72 below the electromagnet assembly 91. The suspension rings 79 and 80 are preferably sized and shaped such that when the suspension rings 79 and 80 are positioned around the actuator assembly 95, there is a gap of no less than 0.5mm between the actuator assembly 95 and the suspension rings 79 and 80.

The first and second suspension rings 79, 80 may comprise stainless steel having elastic properties and exhibiting a spring force when deflected in a direction perpendicular to the spring plane. The first and second suspension rings 79, 80 may be substantially rigid with respect to tangential forces applied to the suspension rings. In this way, the first and second suspension rings 79, 80 may exhibit spring tension when deformed up and down relative to the vertical axis of the actuator assembly but may rigidly resist movement along any other axis (e.g., tilting or twisting movement).

Magnetic ring assembly 76 may have an annular shape and concentrically surround actuator assembly 95. The magnetic ring 88 may comprise one or more materials exhibiting magnetic properties, such as iron, nickel, cobalt, or various alloys. The magnetic ring 88 may be made of a single unitary component or include several magnetic components coupled together. The magnetic ring assembly 76 may be sized and shaped such that when it is positioned concentrically over the actuator assembly 95, there is a gap of no less than 0.5mm between the outer lateral surface of the actuator assembly 95 and the inner surface of the magnetic ring assembly 76.

The magnetic ring assembly 76 can be concentrically positioned around the actuator assembly 95 between the first and second suspension rings 79, 80 and can be rigidly coupled to the first and second suspension rings 79, 80. The magnetic ring assembly 76 can be rigidly coupled to the suspension ring by more than one post 81 evenly spaced around the actuator assembly 95 and configured to extend parallel to the central axis of the pump assembly 70. Suspension rings 79 and 80 and magnet ring assembly 76 may be joined such that magnet ring assembly 76 is suspended equidistant between first and second electromagnetic coils 77 and 78 when the suspension rings have a non-deflected shape. Each of the suspension rings 79 and 80 and magnetic ring holder portions 89 and 90 may include a post receiving area for engagement with the post 81 or may be affixed to the post 81 in any suitable manner that results in the suspension rings 79 and 80 and the magnetic ring assembly 76 being rigidly affixed to the post 81. The posts 81 may extend beyond the suspension rings 79 and 80 to engage other components, such as the flange portion 87 and the membrane assembly 82.

The first electromagnetic coil 77 may be activated by the controller applying an electrical signal from the battery 40 to the first electromagnetic coil 77, inducing a current in the electromagnetic coil and generating a magnetic field around the electromagnetic coil 77. The direction of current in electromagnetic coil 77 and the polarity of magnetic ring assembly 76 closest to electromagnetic coil 77 may be configured such that the first electromagnetic coil magnetically attracts or repels magnetic ring assembly 76, as desired. Similarly, a magnetic field may be generated in second electromagnetic coil 78 by introducing a current in the second electromagnetic coil. The direction of the current in second electromagnetic coil 78 and the polarity of magnetic ring assembly 76 closest to second electromagnetic coil may also be similarly configured such that when an appropriate current is induced in second electromagnetic coil 78, first electromagnetic coil 77 magnetically attracts or repels magnetic ring assembly 76.

Since magnet ring assembly 76 may be rigidly affixed to post 81, which in turn may be rigidly affixed to first and second suspension rings 79, 80, the resilient nature of the suspension rings allows magnet ring assembly 76 to move up towards first electromagnetic coil 77 or down towards second electromagnetic coil 78, depending on the polarity of the magnetic field generated by the electromagnetic rings. In this way, when the magnetic ring assembly 76 experiences an upward magnetic force, the magnetic ring assembly 76 deflects upward toward the first electromagnetic coil 77. As post 81 moves upward with magnetic ring assembly 76, post 81 causes suspension rings 79 and 80 to elastically deform, which generates a spring force opposite the direction of movement. When the magnetic field generated by the first electromagnetic coil disappears, this downward spring force causes the magnetic ring assembly to return to its neutral position when the current is stopped. Similarly, when magnetic ring assembly 76 is magnetically attracted downward, magnetic ring assembly 76 deflects downward toward second electromagnetic coil 78. As post 81 moves downward with magnetic ring assembly 76, post 81 exerts elastic deformation of the first and second suspension rings, creating a spring force in the opposite direction. When the magnetic field generated by the second electromagnetic ring disappears, this upward spring force causes the magnetic ring assembly to return to its neutral position again when the current ceases.

Solenoids 77 and 78 may be energized separately, or alternatively, may be connected in series to cause the solenoids to activate simultaneously. In this configuration, the first magnetic coil may be configured to experience an opposite current direction as the second electromagnetic coil. Thus, when a current is induced to first electromagnetic coil 77 to attract magnetic ring assembly 76, the same current is applied to second electromagnetic coil 78 to induce a current that causes second electromagnetic coil 78 to repel magnetic ring assembly 76. Similarly, when a current is induced to second electromagnetic coil 78 to attract magnetic ring assembly 76, the current applied to first electromagnetic coil 77 causes the first electromagnetic coil to repel magnetic ring assembly 76. In this way, electromagnetic coils 77 and 78 work together to cause deflection of magnetic ring assembly 76.

By manipulating the timing and strength of the electrical signal applied to the electromagnetic coils, the frequency at which the magnetic ring assembly 76 is deflected toward the first and second electromagnetic coils can be altered. For example, by alternating the current induced in the electromagnetic coil more frequently, the magnetic loop assembly may be caused to cycle up and down more times in a given period. By increasing the amount of current, the magnetic loop assembly can deflect at a faster rate and can be made to travel longer distances.

Alternatively, the first electromagnetic coil 77 and the second electromagnetic coil 78 may be energized independently. For example, the first electromagnetic coil 77 and the second electromagnetic coil 78 may be energized at different intensities; one may be tuned to decrease in intensity as the other increases in intensity. In this way, as the strength of the signal applied to first electromagnetic coil 77 causes a reduced upward magnetic attraction, the strength of the signal applied to second electromagnetic coil 78 to cause a downward magnetic attraction may be simultaneously increased.

According to one aspect of the present invention, movement of the magnet ring assembly 76 may be transferred to a membrane assembly 82 that may be disposed concentrically below the stator assembly 72. The membrane assembly 82 is preferably rigidly attached to the magnet ring assembly 76 by posts 81. In the embodiment depicted in fig. 9, the post 81 may extend beyond the second suspension ring 80 and couple to the membrane assembly 82.

Referring now to FIG. 10, one embodiment of the membrane assembly 82 is described in more detail. The membrane assembly 82 may include a rigid membrane ring 96 and a membrane 97. The rigid membrane ring 96 exhibits rigid properties under typical forces experienced during the entire operating range of the present invention. Post receiving locations 98 may be formed into the rigid membrane ring 96 to engage the membrane assembly 82 with the posts 81. Alternatively, the posts 81 may be attached to the rigid membrane ring 96 in any other manner that translates the motion of the magnetic ring assembly 76 to the rigid membrane ring 96. A rigid membrane ring 96 may be affixed to the membrane 97 and hold the membrane in tension. The membrane 97 may be molded directly onto the rigid membrane ring 96 or may be affixed to the rigid membrane ring 96 in any manner that maintains the membrane 97 uniformly tensioned along its circumference. The membrane 97 may alternatively comprise a flexible folded structure, where it is attached to the rigid membrane ring 96 to increase the ability of the membrane to move, where the membrane is affixed to the rigid membrane ring 96. The membrane 97 may further comprise a circular hole 99 disposed in the center of the membrane.

In a preferred embodiment, the membrane 97 has a thin, planar shape and is made of an elastomer with elastic properties and good durability. Alternatively, the membrane 97 may have a uniform thickness from the membrane ring to the circular hole. As yet a further alternative, the thickness of the membrane 97 may vary and exhibit more complex geometries. For example, as shown in fig. 10, the membrane 97 may have a reduced thickness as it extends from the rigid membrane ring 96 to the circular aperture 99. Alternatively or additionally, the membrane 97 may incorporate a metal element (e.g., a coil spring) to enhance the spring force of the membrane in a direction perpendicular to the plane of the membrane, and this spring force may vary radially along the membrane. In yet another embodiment, the membrane 97 may be pre-formed with an undulating shape.

FIG. 11 depicts the moving portions of the embodiment of pump assembly 70 shown in FIGS. 6-9 as a non-ashing element. The non-moving portion of the pump assembly, including the actuator assembly 95 and electromagnet assembly 91 (partially shown), may be secured to the pump housing 27 by a securing ring 71. The moving portion of the pump assembly 70 may include a post 81, a first suspension spring 79, a magnetic ring assembly 76, a second suspension spring 80, and a membrane assembly 82. As the magnetic ring assembly 76 moves up and down, the movement is rigidly transferred to the membrane assembly 82 by the posts 81. Considering the rigidity of the column, when the magnet ring assembly 76 travels a certain distance up or down, the membrane assembly 82 may travel the same distance. For example, when the magnet ring assembly 76 travels 4mm from a position near the electromagnetic coil 77 to a position near the second electromagnetic coil 78, the membrane assembly 82 may also travel 4mm in the same direction. Similarly, the frequency at which the magnetic ring assembly 76 traverses the space between the first and second electromagnetic coils may be the same as the frequency at which the membrane assembly 82 travels the same distance.

Referring now to fig. 12, in the embodiment of the implantable pump 20 described in fig. 6-9, blood can enter the implantable pump 20 from the left ventricle through the inlet cannula 21 and flow down the pump assembly 70 into the delivery channel 100, which is defined by the inner surface of the pump housing 27 and the exterior of the pump assembly 70. Delivery channel 100 begins at the top of stator assembly 72 and extends between tapered section 83 and the interior of pump housing 27. As the blood moves down to the tapered section 83, it is directed through the gap 74 and into the vertical portion of the delivery channel 100 in the region between the pump housing 27 and the actuator assembly 95, and is included in the gap between the magnetic ring assembly 76 and the electromagnet assembly 91. The delivery channel 100 extends down to the flange portion 87 of the stator assembly 72, which routes blood into the flow channel 101 within which the membrane assembly 82 is suspended. The delivery channel 100 delivers blood to the membrane assembly 82 by directing blood from the inlet cannula 21 through the delivery channel 100 to the flow channel 101. By actuating the electromagnetic coils 77 and 78, the membrane 97 may undulate within the flow channel 101 to cause a wave formation in the membrane 97 moving from the membrane edge towards the circular aperture 99. Thus, when blood is delivered from the delivery channel 100 to the membrane assembly 82, it may be advanced radially along both the top and bottom of the membrane 97 toward the circular aperture 99 and from there out of the outlet 23.

According to one aspect of the invention, the undulating membrane pump described herein avoids thrombus formation by placing all moving parts directly within the primary flow path thereby reducing the risk of flow stagnation. In particular, the moving components depicted in fig. 11, including the magnetic ring assembly 76, suspension rings 79 and 80, posts 81, and membrane assembly 82, are all positioned within the delivery channel 100 and flow channel 101. Flow stagnation can be further avoided by eliminating secondary flow paths that can experience significantly slower flow rates.

Turning now to fig. 13 and 14, the lower portion of the implantable pump 20 including the flange portion 87, the membrane assembly 82, and the lower housing portion 23 is shown. The delivery channel 100 may be in fluid communication with the membrane assembly 82 and the flow channel 101, which is defined by the bottom surface of the flange portion 87 and the inner surface of the lower housing portion 25. The flange portion 87 may include a feature 102 that extends downward when the flange portion 87 is moved radially inward. The inner surface of the lower housing portion 25 may also be inclined upwardly as it extends radially inwardly. The combination of the upward slope of the inner surface of the lower housing portion 25 and the downward movement of the bottom surface of the flange portion 87 narrows the flow passage 101 because the passage moves radially inward from the delivery passage 100 to the circular aperture 99 of the membrane 97 disposed around the pump outlet 23.

As explained above, the membrane assembly 82 may be suspended by the posts 81 within the flow channel 101 below the bottom surface of the flange portion 87 and above the inner surface of the lower housing portion 25. The membrane assembly 82 can move freely up and down in the vertical direction within the flow channel 101, this movement being limited only by the suspension rings 79 and 80. The membrane assembly 82 may be restrained by the rigid posts 81 and suspension rings from twisting, tilting, or moving in any direction in the flow channel 101 (other than up and down).

The flow path 101 is divided into an upper flow path and a lower flow path by the membrane 97. The geometry of the membrane 97 may be angled such that the top surface of the membrane 97 is parallel to the bottom surface of the flange portion 87 and the bottom surface of the membrane 97 is parallel to the opposing surface of the lower housing portion 25 when the membrane assembly 82 is at rest. Alternatively, the membrane 97 may be sized and shaped such that when the membrane assembly 82 is stationary, the upper and lower flow channels narrow as they move radially inward from the delivery channel 100 to the circular aperture 99 in the membrane 97.

Referring now also to fig. 14, as the rigid membrane ring 96 is caused to move up and down in the flow channel 101 by the posts 81, the outermost portion of the membrane 97 closest to the rigid membrane ring 96 moves up and down with the rigid membrane ring 96. The membrane 97 (which is flexible and has elastic properties) causes the up and down movement of the portion of the membrane closest to the rigid membrane ring 96 to be gradually translated along the membrane 97 towards the circular aperture 99. This movement across the flexible membrane 97 causes a wave-like deformation in the membrane, which may propagate inwardly from the rigid membrane ring 96 toward the aperture 99.

The waves formed in the undulating membrane may be manipulated by varying the speed at which the rigid membrane ring 96 moves up and down and the distance at which the rigid membrane ring 96 moves up and down. As explained above, the amplitude and frequency of the up and down movement of the rigid membrane ring 96 is determined by the amplitude and frequency of the reciprocation of the magnetic ring assembly 76 over the electromagnet assembly 91. Thus, the waves formed in the undulating film may be tuned by varying the frequency and amplitude at which magnetic ring assembly 76 reciprocates.

When blood is introduced from the delivery channel 100 into the flow channel 101, the fluctuations in the membrane 97 cause the blood to advance toward the circular aperture 99 and exit the pump housing 27 via the outlet 23. Energy transfer from the membrane to the blood is directed radially inward along the length of the membrane toward the aperture 99 and pushes the blood along the flow channel along both sides of the membrane 97 toward the outlet 23.

Fig. 13 and 14 show that as the rigid membrane ring 96 moves downward with the magnetic ring assembly 76, the upper portion of the flow channel 101 near the delivery channel 100 enlarges, causing blood from the delivery channel 100 to fill the upper portion of the flow channel near the outer region of the membrane 97. As the rigid membrane ring 96 moves upward, the upper portion of the flow channel 101 begins to narrow near the rigid membrane ring 96, causing the undulating deformation to be transferred across the membrane. As the wave propagates across the membrane 97, blood in the upper portion of the flow channel 101 is pushed toward the circular aperture and eventually exits the pump housing 27 through the outlet 23. At the same time, as the rigid membrane ring 96 moves upward, the lower portion of the flow channel 101 closest to the exterior of the membrane 97 begins to expand, allowing blood to flow from the delivery channel 100 into this region. Subsequently, when the rigid membrane ring 96 is pushed down again, the lower region of the flow channel 101 closest to the outside of the membrane 97 begins to narrow, causing a wave-like deformation to be transferred across the membrane, which pushes blood towards the outlet 23.

By manipulating the wave formed in the undulating membrane by varying the frequency and amplitude of the up and down movement of magnetic ring assembly 76, the pressure gradient within flow channel 101 and ultimately the flow rate at which blood moves through flow channel 101 can be adjusted. Proper control of the movement of the magnetic ring assembly 76 allows the oxygen-enriched blood to be efficiently and safely pumped from the left ventricle to the aorta and throughout the body as needed.

In addition to pumping blood only from the left ventricle to the aorta, the implantable pump 20 of the present invention can be operated to accurately mimic physiologic pulsatility without loss of pump efficiency. In the embodiments detailed above, pulsatility can be achieved almost instantaneously by changing the frequency and amplitude of the magnetic ring assembly 76 movement to produce a desired flow output or by stopping the movement of the magnetic ring assembly for a period of time to produce periods with low or no flow output. Unlike typical rotary pumps that require some period of time to reach a set number of rotations per minute to achieve a desired fluid displacement and pulsatility, implantable pump 20 can almost instantaneously reach a desired flow output and similarly can almost instantaneously stop output due to the very low inertia created by the small moving masses of the moving components of the pump assembly. The ability to start and stop as needed allows for rapid changes in pressure and flow. The duty cycle, defined by the percentage of time that the membrane 97 is excited over a set period of time, along with the frequency and amplitude can be adjusted to achieve the desired flow output and pulsatility without loss of pump efficiency. Even with the frequency and amplitude kept constant, the flow rate can be altered by manipulating the duty cycle between 0 and 100%.

According to another aspect of the present invention, the controller 30 can be programmed by the programmer 50 to operate at a selected frequency, amplitude and duty cycle to achieve a wide range of physiological flow rates and with physiological pulsing. For example, programmer 50 may direct controller 30 to operate implantable pump 20 at a given frequency, amplitude, and/or duty cycle during periods when the patient is typically asleep and may direct controller 30 to operate implantable pump 20 at a different frequency, amplitude, and/or duty cycle during periods when the patient is typically awake. The controller 30 or implantable pump may also include an accelerometer or position indicator to determine whether the patient is supine or ambulatory, the output of which may be used to move from one set of pump operating parameters to another. When the patient experiences some discomfort or the physician determines that the parameters are not optimal, the physician may alter one or more of at least the frequency, amplitude, and duty cycle to achieve the desired functionality. Alternatively, the controller 30 or the mobile device 60 may be configured to alter one or more of the frequency, amplitude, and duty cycle to accommodate the needs of the patient.

Implantable pump 20 further may include one or more additional sensors for adjusting flow output and pulsatility according to patient demand. The sensor may be incorporated into the implantable pump 20 or alternatively or additionally may be implanted elsewhere in or on the patient. The sensor is preferably in electrical communication with the controller 30 and may monitor a physiological sensor that measures an operating parameter of the performance of the implantable pump 20 or that measures a physiological parameter of the patient (e.g., heart rate or blood pressure). By using one or more physiological sensors, pulsatile flow can be synchronized with the patient's cardiac cycle by, for example, monitoring blood pressure or muscle contraction and synchronizing the duty cycle according to the sensed output.

The controller 30 may compare the physiological sensor measurements to the current implantable pump output. If the demand exceeds the current output as determined by analyzing the sensor measurements, the frequency, amplitude, and/or duty cycle may be automatically adjusted to meet the current demand. Similarly, the controller may determine that the current output exceeds demand and therefore alter the output by changing the frequency, amplitude, and/or duty cycle. Alternatively or additionally, an alarm may be issued from the controller 30 when it is determined that the demand exceeds the current output. Similarly, operational measurements from operational sensors may be compared to predetermined thresholds and an alarm may be issued from the controller 30 in the event that the measurements exceed the predetermined thresholds or a fault is detected.

The implantable pump 20 is sized and shaped to generate physiological flow rates, pressure gradients, and pulsatility at the operating point where maximum efficiency is achieved. In particular, implantable pump 20 may be sized and shaped to produce a physiological flow rate ranging from 4 to 6 liters per minute at a pressure gradient below a threshold associated with hemolysis. Moreover, to mimic a typical physiological pulse of 60 times per minute, the implantable pump 20 may pulse about once per second. To achieve this pulsatility, a 50% duty cycle may be utilized, with an "on" period of 0.5 seconds and an "off period of 0.5 seconds. For a given system, maximum efficiency at a particular operating frequency, amplitude and voltage can be achieved when a flow rate of 4 to 6 liters per minute is produced at a 50% duty cycle by manipulating one or more of the shape and size of the blood flow channel, the elastic properties of the suspension ring, the mass of the moving parts, the membrane geometry and the elastic and frictional properties of the membrane. In this manner, the implantable pump 20 can be designed to produce a desired physiological output while continuing to operate at optimal operating parameters.

By adjusting the duty cycle, the implantable pump 20 can be configured to produce a wide range of output flows at physiological pressure gradients. For example, for an exemplary LVAD system configured to produce 4 to 6 liters per minute at a duty cycle of 50%, the optimal operating frequency may be 120 Hz. For this system, the flow output may be increased to 10 liters per minute or decreased to 4 liters per minute, for example, by only changing the duty cycle. Since the duty cycle and frequency operate independently of each other, the duty cycle can be manipulated between 0 and 100% without affecting the 120Hz frequency.

The implantable pump systems described herein, tuned to achieve physiological flow rates, pressure gradients, and pulsatility, also avoid hemolysis and platelet activation by exerting low to moderate shear forces on the blood, similar to that exerted by a healthy heart. The moving components are rigidly affixed to each other and do not incorporate any parts (e.g., mechanical bearings or gears) that would cause friction. In the embodiments detailed above, the delivery channel 100 can be sized and configured to avoid friction between the moving magnetic ring assembly 76, the suspension rings 79 and 80, the posts 81, and the lower housing portion 25, also by sizing the channel such that a gap of at least 0.5mm is maintained between all moving components. Similarly, magnetic ring assembly 76, suspension rings 79 and 80, and post 81 are all offset from stator assembly 72 by at least 0.5mm to avoid friction between the stator assembly and moving parts.

While various illustrative embodiments of the invention have been described above, it will be apparent to those skilled in the art that various changes and modifications can be made in the embodiments without departing from the invention. For example, the pump assemblies 70 shown in FIG. 9 may have a different order and may include additional or fewer components of various sizes and compositions. It is intended by the appended claims to cover all such changes and modifications that fall within the true spirit and scope of the invention.

Claims (18)

1. An implantable blood pump, comprising:

a housing having an inlet and an outlet and configured to be implanted at a heart of a patient;

a membrane assembly disposed within the housing proximal to the outlet, the membrane assembly including a tensioned flexible membrane coupled to a rigid ring, the tensioned flexible membrane having a central bore;

an actuator disposed within the housing, the actuator having a stator assembly and an electromagnet assembly configured to selectively generate a magnetic field; and

a magnetic ring coupled to the rigid ring, the magnetic ring suspended concentrically around the actuator and configured to reciprocate in response to the magnetic field,

wherein during operation, blood enters the inlet, flows around the actuator and the magnetic ring, and is urged across the membrane to the outlet.

2. The implantable blood pump of claim 1, further comprising first and second suspension rings disposed concentrically about and coupled to the actuator and the magnetic ring.

3. The implantable blood pump of claim 2, wherein the magnetic ring is coupled to each of the membrane assembly and the first and second suspension rings by a plurality of posts.

4. The implantable blood pump of claim 2, wherein the first and second suspension rings allow the magnetic ring to reciprocate over the actuator.

5. The implantable blood pump of claim 4, wherein the first and second suspension rings exert a spring force on the magnetic ring as the magnetic ring reciprocates over the actuator.

6. The implantable blood pump of claim 1, further comprising a securing ring concentrically coupled to the actuator, the securing ring configured to anchor the actuator within the housing.

7. The implantable blood pump of claim 1, wherein a bottom surface of the actuator and an interior of the housing adjacent the outlet form a flow channel, the tensioned flexible membrane suspended within the flow channel.

8. The implantable blood pump of claim 7, wherein the bottom surface of the actuator restricts the flow channel as the flow channel approaches the central aperture in the tensioned flexible membrane.

9. The implantable blood pump of claim 7, wherein the interior of the housing restricts the flow path when the flow path is proximate to the outlet.

10. The implantable blood pump of claim 7, wherein the actuator and an inner surface of the housing adjacent to the inlet form a delivery channel extending from the inlet to the flow channel.

11. The implantable blood pump of claim 1, wherein the magnetic ring is configured to cause an undulating deformation in the tensioned flexible membrane by reciprocating over the actuator.

12. The implantable blood pump of claim 11, wherein the undulating deformation caused corresponds to a distance the magnetic ring reciprocates over the actuator and a frequency at which the magnetic ring reciprocates over the actuator.

13. The implantable blood pump of claim 12, wherein a blood flow rate is adjusted by manipulating a distance the magnetic ring reciprocates over the actuator and a frequency the magnetic ring reciprocates over the actuator.

14. The implantable blood pump of claim 1, wherein electromagnet assembly further comprises first and second electromagnetic coils and causes the magnetic ring to move when at least one of the first and second electromagnetic coils is energized.

15. An implantable blood pump system, comprising:

a controller;

a rechargeable battery operably coupled in electrical communication with the controller; and

a blood pump operably coupled in electrical communication with the controller, the blood pump comprising:

a housing having an inlet and an outlet and configured to be implanted at a heart of a patient;

a membrane assembly disposed within the housing proximal to the outlet, the membrane assembly including a tensioned flexible membrane coupled to a rigid ring, the tensioned flexible membrane having a central bore;

an actuator disposed within the housing, the actuator having a stator assembly and an electromagnet assembly configured to selectively generate a magnetic field; and

a magnetic ring coupled to the rigid ring, the magnetic ring suspended concentrically around the actuator and configured to reciprocate in response to the magnetic field,

wherein during operation, blood enters the inlet, flows around the actuator and the magnetic ring, and is urged across the membrane to the outlet.

16. The implantable blood pump system of claim 15, wherein the controller is programmed to operate the actuator to cause a wave-like deformation in the tensioned flexible membrane by causing the magnetic ring to reciprocate over the actuator.

17. The implantable blood pump system of claim 16, wherein the controller is programmed to operate the actuator to cause the membrane to advance blood from the inlet to the outlet with a pulsatile flow.

18. The implantable blood pump system of claim 17, further comprising a programmer configured to communicate with the controller to set and change operating parameters of the actuator.