Patent Description:
The present invention relates generally to heart pumps and more particularly to implantable pumps having an approximately rectangular profile that employ a membrane to propel blood through the pump.

The human heart is comprised of four major chambers with two ventricles and two atria. Generally, the right-side heart receives oxygen-poor blood from the body into the right atrium and pumps it via the right ventricle to the lungs. The left-side heart receives oxygen-rich blood from the lungs into the left atrium and pumps it via the left ventricle to the aorta for distribution throughout the body. Due to any of a number of illnesses, including coronary artery disease, high blood pressure (hypertension), valvular regurgitation and calcification, damage to the heart muscle as a result of infarction or ischemia, myocarditis, congenital heart defects, abnormal heart rhythms or various infectious diseases, the left ventricle may be rendered less effective and thus unable to adequately pump oxygenated blood throughout the body.

The Centers for Disease Control and Prevention (CDC) estimates that about <NUM> million people in the United States suffer from some form of heart failure. Heart failure is generally categorized into four different stages with the most severe being end stage heart failure. End stage heart failure may be diagnosed where a patient has heart failure symptoms at rest in spite of medical treatment. Patients may have systolic heart failure, characterized by decreased ejection fraction. In patients with systolic heart failure, the walls of the ventricle are weak and do not squeeze as forcefully as a healthy patient. Consequently, during systole a reduced volume of oxygenated blood is ejected into circulation, a situation that continues in a downward spiral until death. Patients may alternatively have diastolic heart failure (HFpEF) wherein the heart muscle becomes stiff or thickened making it difficult for the affected chamber to fill with blood. A patient diagnosed with end stage heart failure has a one-year mortality rate of approximately <NUM>%.

There is a category of patients who exhibit an advanced stage of heart failure but have not yet achieved end stage heart failure. Patients in this category may have severely symptomatic heart failure but some preserved end-organ function. Typically, the condition of these patients deteriorates rapidly over a short period of time and may ultimately require a left ventricular assist device (LVAD) and/or a heart transplant. Presently, the only alternative to a heart transplant is a mechanical implant. While in recent years mechanical implants have improved in design, typically such implants will prolong a patient's life by a few years at most, and include a number of co-morbidities.

Fortunately, patients who have not yet reached end stage heart failure may avoid or prolong a full-support LVAD and/or heart transplant by implantation of a smaller pump. Patients in this category whose condition does not yet warrant a conventional full-support LVAD could be treated effectively with partial-support assist devices providing partial flow support and requiring less invasive surgery. For comparison, implantation of an LVAD device typically requires sternotomy and cardiopulmonary bypass.

One such partial-support assist device is the CircuLite Synergy Micro-pump device. The CircuLite Synergy Micro-pump device provides partial flow support and may serve as a bridge to LVAD implantation or heart transplantation. The CircuLite device, similar to the devices described in at least <CIT> and <CIT>, has a cylindrical shape similar to a AA battery and incorporates a rotary pump having an impeller. The pump is designed to move up to <NUM> liters of blood per minute and to deliver oxygenated blood directly from the left atrium to the subclavian artery. To connect the pump to the patient's vasculature, an ePTFE graft is positioned between the pump outlet and the subclavian artery to delivery oxygenated blood thereto, while an inflow cannula is surgically connected between the pump inlet and the left atrium.

While the CircuLite device offers patients an alternative that provides clinical benefits, several problems with the device have been documented. One problem observed during clinical testing of the CircuLite device is failure due to thrombosis. The CircuLite device employs an impeller and has a size comparable to that of a AA battery, roughly <NUM> x <NUM>. To produce an output flow of up to <NUM> liters of blood per minute, the impeller - which has a diameter of roughly <NUM> - must be rotated at high RPM. However, the higher the RPMs, the greater the shear stress applied to the blood and thus the greater the risk of thrombosis.

Yet another problem with the CircuLite device is the configuration of the inflow cannula and the need to insert the inlet into the left atrium. Unlike the left ventricle, which is thick and muscular, the atrial wall is relatively thin and fragile. For this reason, an inflow cannula ring cannot be used to fix the cannula to the heart chamber. As a result, it was observed that the cannula insertion site is prone to leakage. Also, with a diameter of roughly <NUM>, and a mostly circular cross-section, the CircuLite device noticeably protrudes from the chest of the patient, which some patients may find unaesthetic.

Other partial-support pump devices suffer from problems similar to the CircuLite Synergy device. HeartWare produces a device similar to the CircuLite device, but which has a diameter of <NUM>. The HeartWare product is believed to suffer from the same shortcomings as the CircuLite device.

Other partial-support pump devices have a cylindrical shape and utilize a centrifugal pump having an impeller such as the one described in <CIT> which is assigned to CircuLite and Foundry LLC. The implantable pump described in the '<NUM> patent provides partial circulatory support much like the CircuLite Synergy device. Yet, another partial-support pump device is Abiomed's Symphony device, which employs a centrifugal pump and is also implanted in the chest region.

Other types of partial-support pump devices are known that accelerate blood axially. For example, Abiomed's Impella pump, similar to the pump described in <CIT>, is cylindrical in shape and pulls blood into an inlet area at one end. As described in the `<NUM> patent, the pump involves an axial flow pump having a number of blades extending from a hub that accelerate the blood, which is expelled from an opposing end. While Abiomed's Impella pump is intended to be implanted in the left ventricle and aorta, a similar device by Procyrion, the Aortix device, works in a similar fashion but is an intra-aortic pump that is suspended in the aorta. <CIT> and <CIT> to Procyrion describe pumps similar to the Aortix device and discuss axial flow pumps having an impeller to propel blood from one of its ends to the other.

<CIT>) relates to a vibrating membrane fluid circulator made up of an admission orifice, a pump body and a delivery orifice, the pump body having two rigid walls defining therebetween a circulation space for fluid circulation from the admission to the delivery orifice.

While all the foregoing devices are partial-support pump devices that may result in clinical benefits, each of the partial-support pump devices share similar shortcomings with the CircuLite Synergy device. Specifically, each of these pumps have a relatively small blade or impeller that rotates at a high rate of speed to partially support blood circulation. For the reasons discussed above with regard to CircuLite, these pumps too are believed to present an increased risk of thrombosis caused by excessive shear stress and trauma to the blood cells, and risk of platelet activation. Furthermore pumps like the Abiomed's Symphony device generate an unpleasant noise when in use.

Accordingly, there is a need for an energy efficient implantable pump having light weight, small size, and a delivery mechanism for partially support blood circulation with minimal blood damage.

The present invention overcomes the drawbacks of previously-known partial-support assist devices and methods by providing an implantable pump system having an undulating membrane capable of producing a wide range of flow rates while applying low shear forces to the blood, thereby reducing hemolysis and platelet activation relative to previously-known systems.

The implantable pump system of the present invention is particularly well-suited for use as a partial-support assist device and includes an undulating membrane pump particularly suitable for partial-support circulation in a patient having heart failure at a stage that does not warrant implantation of a left ventricle assist device (LVAD) or heart transplantation. The pump system may also be suitable for patients exhibiting heart failure with reduced ejection fraction (HFrEF) who in the later stage may benefit from an LVAD as well as patients that exhibit heart failure with preserved ejection fraction (HFpEF) who currently do not benefit from LVAD. An implantable pump system constructed in accordance with the principles of the present invention may include an implantable pump, a battery and controller as well as an extracorporeal programmer. The implantable pump preferably includes a housing having an inlet and an outlet, a flexible membrane, and an electromagnetic actuator having electromagnetic portions and a magnet portion. When configured as a partial-support assist device, an inlet cannula may be inserted into a patient's left atrium and an outlet cannula may be placed in fluid communication with the patient's subclavian artery. By activating the electromagnetic actuator within the implantable pump, the membrane is induced to undulate, thereby causing blood to be drawn into the pump through the inlet cannula and expelled through the outlet cannula into the subclavian artery. Flow rate and pulsatility may be manipulated by changing one or more of the frequency, amplitude and duty cycle of the electromagnetic actuator assembly.

The membrane pump described herein overcomes the shortcomings in the prior art by achieving desirable flow rates for partial circulatory support in a manner causing minimal blood damage, thereby avoiding the problems with thrombus formation that plagued earlier partial-support assist devices. The implantable pump described herein is an improvement over <CIT>, <CIT>, <CIT> and <CIT>, which generally disclose vibrating membrane fluid circulators. More specifically, these patents disclose a deformable membrane disposed within a structure having an admission orifice and a delivery orifice. At the admission end, the membrane is attached to a member that provides an excitation force to the membrane, causing waves in the membrane to travel toward the delivery orifice, thereby transferring energy to fluid within the structure and ultimately directing the fluid out of the delivery orifice. The present invention incorporates the teachings of these patents into the implantable pump system described herein for use as a partial-support assist device.

Referring now to <FIG>, pump system <NUM> constructed in accordance with the principles of the present invention is described. System <NUM> illustratively includes implantable pump <NUM>, controller <NUM>, battery <NUM>, programmer <NUM> and optionally, a software module programmed to run on mobile device <NUM>. Implantable pump <NUM> is configured to be implanted within the patient and may be positioned into a subcutaneous or intra-muscular pocket inferior to the subclavian artery and in front of the right pectoralis major muscle. Implantable pump <NUM> may be connected to inlet cannula <NUM> and outlet cannula <NUM>. Inlet cannula <NUM> may connect implantable pump <NUM> to a first heart chamber or body lumen, e.g., the left atrium LA of heart H, and outlet cannula <NUM> may connect implantable pump to a second heart chamber or body lumen, e.g., the right subclavian artery SA. Outlet cannula <NUM>, may be any kind of graft suitable for fluid communication between implantable pump <NUM> and subclavian artery SA. For example, outlet cannula <NUM> may be a ePTFE graft or other synthetic material.

Controller <NUM> and battery <NUM> may be extracorporeal and sized so as to be placed on a belt or garment worn by the patient, as illustrated in <FIG>. Battery <NUM> may be electrically coupled to controller <NUM> via a cable that is integrated into the belt. Controller <NUM> and battery <NUM> may be two separate units or may be incorporated into the same unit. Where controller <NUM> and battery <NUM> are extracorporeal, cable <NUM> may be tunneled from the subcutaneous pocket to the right upper quadrant of the abdomen at which point cable <NUM> may exit the body. Accordingly, cable <NUM> may extend from the pump in the subcutaneous pocket, through the body of the patient to the abdomen and out the abdomen and to the extracorporeal controller <NUM> and/or battery <NUM> on the exterior of the body. In this manner, both controller <NUM> and battery <NUM> may be electrically coupled via cable <NUM> to implantable pump <NUM>.

In an alternative embodiment, controller <NUM> and/or battery <NUM> may be enclosed within a biocompatible housing and sized to be implanted subcutaneously in the patient's abdomen or in any other suitable subcutaneous location. In this alternative embodiment, controller <NUM> and/or battery <NUM> may include a wireless transceiver for bi-directional communications with an extracorporeal programming device and/or charging device. Where battery <NUM> is implanted subcutaneously, a second extracorporeal battery may be worn by the patient near implanted battery <NUM> which may charge battery <NUM> transcutaneously. As will be understood, the foregoing alternative embodiment avoids the use of percutaneous cable <NUM>, and thus eliminates a frequent source of infection.

Battery <NUM> preferably comprises a rechargeable battery capable of powering implantable pump <NUM> and controller <NUM> for a period of several hours or even days before needing to be recharged. Battery <NUM> may include a separate charging circuit, not shown, as is conventional for rechargeable batteries. Battery <NUM> preferably is disposed within a housing suitable for carrying on a belt or holster, so as not to interfere with the patient's daily activities. However, as explained above, battery may be implanted and thus battery may be disposed within a biocompatible housing.

Programmer <NUM> is programmed to execute programmed software routines on a computer (e.g., laptop computer, desktop computer, smartphone, tablet, smartwatch, etc.) for use by a clinician or medical professional, for configuring and providing operational parameters to controller <NUM>. The configuration and operational parameter data is stored in a memory associated with controller <NUM> and used by the controller to control operation of implantable pump <NUM>. As described in further detail below, controller <NUM> directs implantable pump <NUM> to operate at specific parameters determined by programmer <NUM>. Programmer <NUM> may be coupled to controller <NUM> via cable <NUM>. Using programmer <NUM>, operational parameters of implantable pump <NUM> are set and periodically adjusted, e.g., when the patient visits the clinician.

In accordance with another aspect of the invention, mobile device <NUM>, which may be a conventional laptop, smartphone, tablet, or smartwatch, may include an application program for bi-directionally and wirelessly communicating with controller <NUM>, e.g., via WiFi or Bluetooth communications. Preferably, mobile device <NUM> is used by the patient or the patient's caretaker. The application program on mobile device <NUM> may be programmed to permit the patient to send instructions to controller <NUM> to modify or adjust a limited number of operational parameters of implantable pump <NUM> stored in controller <NUM>. Alternatively or in addition, mobile device <NUM> may be programmed to receive from controller <NUM> and to display on screen <NUM> of mobile device <NUM>, data relating to operation of implantable pump <NUM> or alert or status messages generated by controller <NUM>.

Referring now to <FIG>, implantable pump <NUM> may be implanted using a surgical approach as is illustrated in <FIG>. The surgical approach involves creating a subcutaneous pocket, e.g., at a position inferior to the subclavian artery and in front of the right pectoralis major muscle, in which implantable pump <NUM> is positioned. An incision is made in the right subclavian artery SA into which an end of outflow cannula <NUM> is positioned. Outflow cannula <NUM> may be anastomosed to the right subclavian artery SA. The opposing end of outflow cannula <NUM> is inserted into the subcutaneous pocket and coupled with implantable pump <NUM>. To reach the heart, a mini-thoracotomy may be performed and pericardium is opened to insert an end of inflow cannula <NUM> into left atrium LA. Inflow cannula <NUM> may be secured to the left atrium using sutures. The opposing end of inflow cannula <NUM> may be tunneled through intercostal space and ultimately into the subcutaneous pocket to be coupled with implantable pump <NUM>.

Alternatively, implantable pump <NUM> may be implanted using an endovascular approach, illustrated in <FIG>. Like in the surgical approach, the endovascular approach involves creating a subcutaneous pocket, e.g., at a position inferior to the subclavian artery and in front of the right pectoralis major muscle, in which implantable pump <NUM> is positioned. The endovascular approach also involves an incision made in the right subclavian artery SA into which an end of outflow cannula <NUM> is positioned and anastomosed to the right subclavian artery SA. The opposing end of outflow cannula <NUM> may similarly be inserted into the subcutaneous pocket and coupled with implantable pump <NUM>. However, unlike the surgical approach described above, to reach the right atrium, inflow cannula <NUM> is inserted through the right subclavian vein. In this approach, an incision is made in the right subclavian vein SV and a guidewire is inserted and advanced through the superior vena cava SVC to right atrium RA. Upon reaching right atrium RA, a transseptal puncture technique may be used to advance the guidewire into left atrium LA. Inflow cannula <NUM> may then be advanced to left atrium LA over the guidewire and may be anchored to the atrial septum.

Referring now to <FIG>, implantable pump <NUM> is illustrated in greater detail. Implantable pump <NUM> includes pump housing <NUM> which is made of a biocompatible material, such as titanium, and is sized to be implanted within a patient's chest as described above. Pump housing <NUM> may have a general rectangular shape or may narrow at one or both ends and may be two or more pieces that fit together by, for example, threads or welding, to form fluid tight pump housing <NUM>. Pump housing <NUM> may have any size suitable for pump assembly <NUM> to be disposed within pump housing <NUM>. Pump housing includes inlet <NUM> and outlet <NUM> through which blood may flow in and out, respectively. Pump housing <NUM> in <FIG> demonstrates a narrowing step-down feature to facilitate blood flow towards outlet <NUM>. Pump also may include electrical port <NUM> to attach implantable pump <NUM> to cable <NUM>. Electrical port <NUM> may permit cable <NUM> to transverse pump housing <NUM> and connect to pump assembly <NUM> in a fluid tight manner. Cable <NUM> may deliver electrical wires from controller <NUM> and battery <NUM> to pump assembly <NUM>.

With respect to <FIG>, controller <NUM> is illustrated in greater detail. As depicted in <FIG>, controller <NUM> may be sized and configured to be worn on the exterior of the patient's body or may be sized and configured to be implanted subcutaneously. Controller <NUM> includes input port <NUM>, output port <NUM>, battery port <NUM>, indicator lights <NUM>, display <NUM>, status lights <NUM> and buttons <NUM>. Input port <NUM> is configured to periodically and removably accept cable <NUM> to establish an electrical connection between programmer <NUM> and controller <NUM>, e.g., via a USB connection. In this manner, a clinician may couple to controller <NUM> to set or adjust operational parameters stored in controller <NUM> for controlling operation of implantable pump <NUM>. In addition, when programmer <NUM> is coupled to controller <NUM>, the clinician also may download from controller <NUM> data relating to operation of the implantable pump, such as actuation statistics, for processing and display on display <NUM> of programmer <NUM>. Alternatively, or in addition, controller <NUM> may include a wireless transceiver for wirelessly communicating such information with programmer <NUM>. In this alternative embodiment, wireless communications between controller <NUM> and programmer <NUM> may be encrypted with an encryption key associated with a unique identification number of the controller, such as a serial number.

Battery port <NUM> is configured to removably accept a cable connected to battery <NUM> which may be incorporated into the belt illustrated in <FIG>. Battery <NUM> may be removed from the belt and disconnected from controller <NUM> to enable the patient to periodically replace the battery with a fully charged battery. It is expected that the patient will have available to him or her at least two batteries, so that while one battery is coupled to controller <NUM> to energize the controller and implantable pump <NUM>, the other battery may be connected to a recharging station. Alternatively, or in addition, battery port <NUM> may be configured to accept a cable that is coupled directly to a power supply, such as a substantially larger battery/charger combination that permits the patient to remove battery <NUM> while lying supine in a bed, e.g., to sleep.

Output port <NUM> is electrically coupled to cable <NUM>, which is coupled to implantable pump <NUM> through electrical port <NUM> of pump housing <NUM>. Cable <NUM> provides energy to energize implantable pump <NUM> in accordance with the configuration settings and operational parameters stored in controller <NUM>. Cable <NUM> also may permit controller <NUM> to receive data from sensors disposed in implantable pump <NUM>. In one embodiment, cable <NUM> is designed to extend percutaneously and may be an electrical cable having a biocompatible coating. Cable <NUM> may be impregnated with pharmaceuticals 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, controller <NUM> may include indicator lights <NUM>, display <NUM>, status lights <NUM> and buttons <NUM>. Indicator lights <NUM> may visually display information relevant to operation of the system, such as the remaining life of battery <NUM>. Display <NUM> may be a digital liquid crystal display that displays real time pump performance data, physiological data of the patient, such as heart rate, and/or operational parameters of the implantable pump, such as the target pump pressure or flow rate, etc. When it is determined that certain parameter conditions exceed preprogrammed thresholds, an alarm may be sounded and an alert may be displayed on display <NUM>. Status lights <NUM> may comprise light emitting diodes (LEDs) that are turned on or off to indicate whether certain functionality of the controller or implantable pump is active. Buttons <NUM> may be used to wake up display <NUM>, to set or quiet alarms, etc..

With respect to <FIG>, the components of the illustrative embodiment of controller <NUM> of <FIG> are described. In addition to the components of controller <NUM> described in connection with <FIG>, controller <NUM> further includes microprocessor <NUM>, memory <NUM>, battery <NUM>, optional transceiver <NUM> and amplifier circuitry <NUM>. Microprocessor <NUM> may be a general purpose microprocessor, for which programming to control operation of implantable pump <NUM> is stored in memory <NUM>. Memory <NUM> also may store configuration settings and operational parameters for implantable pump <NUM>. Battery <NUM> supplies power to controller <NUM> to provide continuity of operation when battery <NUM> is periodically swapped out. Optional transceiver <NUM> facilitates wireless communication with programmer <NUM> and/or mobile device <NUM> via any of a number of well-known communications standards, including BLUETOOTH™, ZigBee, and/or any IEEE <NUM> wireless standard such as Wi-Fi or Wi-Fi Direct. Controller <NUM> may further include amplifier circuitry <NUM> for amplifying electrical signals transferred between controller <NUM> and implantable pump <NUM>.

Referring now to <FIG>, battery <NUM> is described. Battery <NUM> provides power to implantable pump <NUM> and also may provide power to controller <NUM>. As described above, battery <NUM> may be implanted subcutaneously or may be extracorporeal. Battery <NUM> may consist of a single battery or a plurality of batteries disposed within a housing, and when configured for extracorporeal use, is sized and configured to be worn on the exterior of the patient's body, such as on a belt. Alternatively, where battery <NUM> is implanted into a patient, battery <NUM> may be disposed in a biocompatible housing. Battery life indicator <NUM> may be provided on the exterior of battery <NUM> to indicate the remaining charge of the battery. Controller may be connected to battery <NUM> via a cable connecting battery port <NUM> of controller <NUM> to output port <NUM> of battery <NUM>. In one embodiment, battery <NUM> may be rechargeable using a separate charging station, as is known in the art of rechargeable batteries. Alternatively, or in addition, battery <NUM> may include port <NUM> which may be removably coupled to a transformer and cable to permit the battery to be recharged using a conventional residential power outlet, e.g., <NUM>/240V, <NUM>/<NUM> AC power.

Referring now to <FIG>, programmer <NUM> is described. Programmer <NUM> may be a conventional laptop, desktop, tablet, smartphone, smartwatch loaded with programmed software routines <NUM> for configuring controller <NUM> and setting operational parameters that controller <NUM> uses to control operation of implantable pump <NUM>. As discussed above, programmer <NUM> typically is located in a clinician's office or hospital, and is coupled to controller <NUM> via cable <NUM> or wirelessly to initially set up controller <NUM>, and then periodically adjust controller <NUM> thereafter as required to adjust the operational parameters as may be needed. The operational parameters of controller <NUM> set using the programmed routines of programmer <NUM> may include but are not limited to applied voltage, pump frequency, pump amplitude, target flow rate, pulsatility, etc. When first implanted, the surgeon or clinician may use programmer <NUM> to communicate initial operating parameters to controller <NUM>. Following implantation, the patient periodically may return to the clinician's office for adjustments to the operational parameters which may again be made using programmer <NUM>.

Programmer <NUM> may be any type of conventional personal computer device having touch screen capability. As illustrated in <FIG>, programmer <NUM> preferably includes processor <NUM>, memory <NUM>, input/output device <NUM>, display <NUM>, battery <NUM> and communication unit <NUM>. Memory <NUM> may be a non-transitory computer readable medium that stores the operating system for the programmer, as well as the programmed routines needed to communicate with controller <NUM>. When executed by processor <NUM>, instructions from the programmed routines stored on the non-transitory computer readable medium cause execution of the functionality described herein. Communication unit <NUM> may include any of a number of well-known communication protocols, such as BLUETOOTH™, ZigBee, and/or any IEEE <NUM> wireless standard such as Wi-Fi or Wi-Fi Direct. As illustrated in <FIG>, the programmed routines used to program and communicate with controller <NUM> also may provide data for display on the screen of programmer <NUM> identifying operational parameters with which controller <NUM> controls implantable pump <NUM>. The programmed routines also may enable programmer <NUM> to download from controller <NUM> operational data or physiologic data communicated by the implantable pump and to display that information in real time while 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 <NUM>.

Referring now to <FIG>, pump assembly <NUM> is illustrated. Pump assembly <NUM> illustratively includes membrane assembly <NUM>, magnet assembly <NUM>, electromagnetic assembly <NUM>, mounting structure <NUM> (not shown), linear guides <NUM> which may optionally include spring system <NUM>. Linear guides <NUM> may permit magnet assembly <NUM> to move up and down linearly along linear guides <NUM>. Spring system <NUM>, discussed in greater detail below with reference to <FIG>, may be configured to apply a spring force toward a neutral center position as magnet assembly <NUM> deviates from the natural position.

Referring now to <FIG>, pump assembly <NUM> is illustrated showing mounting structure <NUM>. Pump assembly <NUM> is sized and configured to fit within pump housing <NUM>. Mounting structure <NUM>, may be mounted to pump housing <NUM> using any well-known fixation technique. For example, mounting structure <NUM> may include threaded grooves that correspond to threaded grooves in pump housing <NUM> and may be coupled to pump housing <NUM> using plurality of screws. Alternatively, mounting structure <NUM> may be welded to pump housing <NUM>.

Mounting structure <NUM> is sized and configured to be disposed within pump housing <NUM> adjacent to inlet <NUM>. Mounting structure <NUM> may have a rectangular shape with a square cross-section. Mounting structure <NUM> may have inlet channel <NUM> which permits blood received at inlet <NUM> to flow through mounting structure <NUM>. Mounting structure <NUM> may include inflow separator <NUM> which may permit blood that enters through inlet channel <NUM> to separate into upper flow channel <NUM> and lower flow channel <NUM>.

Electromagnet assembly <NUM> and linear guides <NUM> may be coupled to or otherwise incorporated into mounting structure <NUM>. Electromagnet assembly <NUM> includes first electromagnet <NUM> and second electromagnet <NUM> each having an electromagnetic winding that exhibits electromagnetic properties when an electrical current is applied. First electromagnet <NUM> may be coupled to upper flange portion <NUM> of mounting structure <NUM> as is illustrated in <FIG>. Second electromagnet <NUM> may similarly be coupled to lower flange portion <NUM>. In this configuration first electromagnet <NUM> may be positioned directly above second electromagnet <NUM> and a gap may exist between first electromagnet <NUM> and second electromagnet <NUM>.

Linear guides <NUM> may be coupled at one end to upper flange portion <NUM> and another end to lower flanged portion <NUM> and may span the gap between first electromagnet <NUM> and second electromagnet <NUM>. Linear guides <NUM> may be arranged parallel to one another and perpendicular to the direction of blood flow through inlet channel <NUM>.

Magnet assembly <NUM> may include upper magnet <NUM> which is configured to move linearly along linear guides <NUM>. Magnet <NUM> may be a permanent magnet and may either be a single magnet or may be may include multiple magnets coupled together to form magnet <NUM>. Magnet <NUM> may be rectangular in shape and may have linear guide receiving portions that extend through magnet <NUM> through which linear guides <NUM> may be inserted and extend through. In this manner, magnet <NUM> may move up towards first electromagnet <NUM> and down towards second electromagnet <NUM>.

Membrane assembly <NUM> may include membrane connector <NUM> and rectangular membrane <NUM>. As discussed in greater detail below, rectangular membrane <NUM>, may be generally rectangular in shape and may be connected to magnet <NUM> at by membrane connector <NUM>. Magnet <NUM> may include a threaded receiving portion through which membrane connector <NUM> in the form of screws may be used to couple an end of rectangular membrane <NUM> to magnet <NUM>. Alternatively, membrane connector <NUM> may be a clamping device that clamps membrane <NUM> to magnet <NUM>. It is understood that membrane connector <NUM> may be any well-known mechanism or techniques, e.g. epoxy, screws, etc..

Membrane <NUM>, coupled to magnet <NUM>, as is illustrated in <FIG>, may move up and down with magnet <NUM>. Spring system <NUM> may optionally be coupled to linear guides <NUM> as illustrated in <FIG>. Spring system may be designed to position magnet <NUM> in a neutral position. For example, the neutral position may be the same plane as inflow separator <NUM>. As such, though magnet <NUM> may travel up and down along linear guides <NUM>, magnet <NUM> may be designed to return to the neutral position.

First electromagnet <NUM> and second electromagnet <NUM> of electromagnetic assembly <NUM> may include one or more smaller metallic wires that may be wound into a coil, and may be in electrical communication with battery and/or controller via cable <NUM> connected via electrical port <NUM>. First electromagnet <NUM> and second electromagnet <NUM> are in electrical communication with one another and are electrically activated independently and may have separate wired connections to controller <NUM> and/or battery <NUM> via cable <NUM>. Current flow applied to first electromagnet <NUM> and second electromagnet <NUM> could be reversed depending on the operating parameters applied. The wires of first electromagnet <NUM> and second electromagnet <NUM> may be insulated to prevent shorting to adjacent conductive material.

Implantable pump housing <NUM> may be comprised of titanium, stainless steel or any other rigid biocompatible material suitable for mounting pump assembly <NUM> to pump housing <NUM>. Magnet assembly <NUM> may be comprised of one or more materials exhibiting magnetic properties such as iron, nickel, cobalt or various alloys. Where multiple magnets make up magnet assembly <NUM>, the magnets may be linked by metallic parts made of a high saturation alloy, such as Vacoflux. Mounting structure too may be made from Vacoflux. The one or more smaller metallic wires wound into a coil in electromagnetic assembly <NUM> may be made of copper or any other metal having appropriate electromagnetic properties.

Referring now to <FIG>, various rectangular membranes are illustrated in greater detail. Rectangular membrane <NUM> may take a general thin rectangular shape. In a preferred embodiment, rectangular membrane <NUM> has a thin, planar shape and is made of an elastomer having elastic properties and good durability. For example, rectangular membrane <NUM> may be flexible through the entire length and cross-section of rectangular membrane <NUM> such that actuation of the implantable pump moves rectangular membrane to create wave-like deformation that pumps blood through the pump. Rectangular membrane <NUM> may have a uniform thickness from one end to the other. As yet a further alternative, rectangular membrane <NUM> may vary in thickness and exhibit more complex geometries, as described further herein. For example, rectangular membrane <NUM> may have a reduced thickness as the membrane extends from one end to the other and/or may have right-angled or beveled or rounded corners. Alternatively, or in addition to, rectangular membrane <NUM> may incorporate metallic elements such as a spring to enhance the spring force of the membrane in a direction normal to plane of the membrane. In yet another embodiment, rectangular membrane <NUM> may be pre-formed with an undulating shape.

<FIG> illustrate various rectangular membranes that may be used in the implantable pumps described herein. As shown, each of the rectangular membranes have protrusions extending from the distal end of the rectangular membrane in a direction orthogonal to the blood flow path. As is illustrated in <FIG>, rectangular membrane <NUM>' has two post receiving portions <NUM> and <NUM>. Post receiving portions <NUM> and <NUM> may have a diameter slightly larger than that of posts <NUM> which may be parallel to linear guides <NUM> and extend from a top side of pump housing <NUM> to a bottom side as shown in <FIG>. Alternatively, posts <NUM> may extend between upper funnel portion <NUM> and lower funnel portion <NUM> as is illustrated in <FIG>. Also, as shown in <FIG>, rectangular membrane <NUM>' has extended portions <NUM> and <NUM> that each protrude from the main body of rectangular membrane <NUM> in a direction parallel to the blood flow path to create a space between extended portions <NUM> and <NUM>. Extended portions <NUM> and <NUM> have post receiving portions <NUM> and <NUM>, respectively, therein and may permit fluid to more freely escape out of outlet <NUM> of implantable pump <NUM>. Alternatively, in <FIG>, the main body of rectangular membrane <NUM>" extends the entire length of the membrane without any extended portions. In <FIG>, the main body of rectangular membrane <NUM>" has two post receiving portions <NUM>' and <NUM>'. In yet another alternative, as shown in <FIG>, rectangular membrane <NUM>‴ does not include the post receiving portions. This may permit the distal end of rectangular membrane <NUM>‴ nearest outlet <NUM> to move more freely.

Referring now to <FIG>, one embodiment of spring system <NUM> is illustrated in greater detail. Spring system <NUM> may optionally be coupled or otherwise incorporated into linear guides <NUM>. As mentioned above, spring system <NUM> may provide a spring force to magnet <NUM> when magnet <NUM> deviates from a neutral position. As illustrated in <FIG> the neutral position may be equidistant between upper flange portion <NUM> and lower flange portion <NUM>. However, spring system <NUM> may be designed to set the neutral position at any position between upper flange portion <NUM> and lower flange portion <NUM>. Spring system <NUM> may include upper spring portion <NUM> and lower spring portion <NUM>. Upper spring portion <NUM> and lower spring portion <NUM> may collectively apply a spring force providing increased resistance as magnet <NUM> deviates from the neutral position.

Referring now to <FIG>, funnel assembly <NUM> is illustrated. Funnel assembly <NUM> may optionally be disposed within pump housing <NUM> near outlet <NUM>, as is illustrated in <FIG>, to further narrow the blood flow through implantable pump <NUM> as blood travels from inlet <NUM> to outlet <NUM>. Funnel assembly <NUM> may include upper funnel portion <NUM> and a lower funnel portion <NUM>. As is illustrated in <FIG>, the thickness of the funnel generally increases towards outlet <NUM>. Additionally, the width of the flow channel may narrow as it moves inward toward outlet <NUM>. Upper funnel portion <NUM> and lower funnel portion <NUM> may include threaded portions that extend the through upper funnel portion <NUM> and lower funnel portion <NUM> or at least partway through to permit the funnel portions to be secured to pump housing <NUM>.

Referring now to <FIG>, sectional views of implantable pump <NUM> are illustrated. In <FIG>, rectangular membrane <NUM> is seen suspended in tension between linear guides <NUM> and posts <NUM>. In this configuration membrane <NUM> is suspended within pump housing <NUM>. As explained above, blood may enter pump housing at inlet <NUM> and travel through mounting structure <NUM> via inlet channel <NUM>. After traveling through inlet channel <NUM>, blood must travel around inflow separator <NUM>. Inflow separator <NUM> separates blood flow into upper flow channel <NUM> and lower flow channel <NUM>. Upper flow channel <NUM> is defined by a top surface of magnet <NUM> and membrane <NUM>, on one side, and an interior surface of pump housing <NUM> on the other side. Lower flow channel <NUM> is defined by a bottom surface of magnet <NUM> and membrane <NUM>, on one side, and an interior surface of pump housing <NUM> on the other side. Upper flow channel <NUM> and lower flow channel <NUM> merge at outlet <NUM>. In this manner, after exiting inlet channel <NUM>, and traveling around inflow separator <NUM>, blood travels along the top and bottom surface of membrane <NUM> until it reaches outlet <NUM>.

Implantable pump may be activated to pump blood from inlet <NUM> to outlet <NUM> by moving magnet <NUM> up and down along linear guides <NUM>. In this manner magnet <NUM> may move up towards first electromagnet <NUM> or down towards second electromagnet <NUM>. To move magnet <NUM> up, current may be applied to first electromagnet <NUM> such that first electromagnet <NUM> generates a magnetic field that attracts magnet <NUM> and thus causes magnet <NUM> to move toward first electromagnet <NUM>. At the same time, second electromagnet <NUM> may be induced with a current that causes second electromagnet <NUM> to generate a magnetic field having the opposite polarity of first electromagnet <NUM>, thereby repelling magnet <NUM> from second electromagnet <NUM> while first electromagnet <NUM> attracts magnet <NUM>. In this manner, first electromagnet <NUM> and second electromagnet <NUM> may work together to move magnet <NUM>. Alternatively, second electromagnet <NUM> may not be energized while first electromagnet <NUM> is energized.

To move magnet <NUM> down, current may be applied to second electromagnet <NUM> such that second electromagnet <NUM> generates a magnetic field that attracts magnet <NUM> and thus causes magnet <NUM> to move toward second electromagnet <NUM>. At the same time, first electromagnet <NUM> may be induced with a current that causes first electromagnet <NUM> to generate a magnetic field having the opposite polarity of second electromagnet <NUM>, thereby repelling magnet <NUM> from first electromagnet <NUM> while second electromagnet <NUM> attracts magnet <NUM>. Alternatively, first electromagnet <NUM> may not be energized while second electromagnet <NUM> is energized.

First electromagnet <NUM> and second electromagnet <NUM> are designed to generate opposite polarities when current is applied in the same direction through first electromagnet <NUM> and second electromagnet <NUM>. In this manner, the same electrical current may be applied simultaneously to first electromagnet <NUM> and second electromagnet <NUM> to achieve the desired effects. Alternatively, first electromagnet <NUM> and second electromagnet <NUM> are designed to generate the same polarity when current is applied in the same direction. In this configuration the same current would not be applied simultaneously to first electromagnet <NUM> and second electromagnet <NUM>.

As spring system <NUM> exhibits a spring force when magnet <NUM> deviates from the neutral position, when first electromagnet <NUM> and/or second electromagnet <NUM> cause magnet <NUM> to move up toward first electromagnet <NUM>, spring system <NUM> may exert a downward spring force on magnet <NUM> toward the neutral position. Similarly, when first electromagnet <NUM> and/or second electromagnet <NUM> cause magnet <NUM> to move downward toward second electromagnet <NUM>, spring system <NUM> may exert an upward spring force on magnet <NUM> toward the neutral position. The further magnet <NUM> deviates from the neutral position, the greater the spring force applied to magnet <NUM>.

By manipulating the timing and intensity of the electrical signals applied to electromagnetic assembly <NUM>, the frequency at which magnet <NUM> moves up and down may be altered. For example, by alternating the current induced in the electromagnetic assembly <NUM> more frequently, magnet <NUM> may be caused to cycle up and down more times in a given period. By increasing the voltage applied to electromagnetic assembly <NUM>, magnet <NUM> may travel at a faster rate and caused to travel longer distances from the neutral position.

As magnet <NUM> is coupled to rectangular membrane <NUM> via membrane connector <NUM>, movement of magnet <NUM> is applied to the end of rectangular membrane <NUM>. <FIG> illustrates movement by magnet <NUM> being applied to rectangular membrane <NUM>. As is shown in <FIG>, a current has been induced in first electromagnet <NUM> and/or second electromagnet <NUM> such that magnet <NUM> is attracted towards first electromagnet <NUM>. The movement of magnet <NUM> has caused the end of membrane <NUM> coupled to magnet <NUM> to also move up and down thereby causing wave-like deformations in membrane <NUM>. By inducing alternating current to first electromagnet <NUM> and second electromagnet <NUM>, membrane <NUM> may be undulated between upper flow channel <NUM> and lower flow channel <NUM> to induce wavelike formations in rectangular membrane <NUM> that moves from the edge of rectangular membrane <NUM> coupled to magnet <NUM> towards outlet <NUM>.

As rectangular membrane <NUM> is attached directly to magnet <NUM>, when magnet <NUM> travels a certain distance upward or downward, the end of rectangular membrane <NUM> attached to magnet <NUM> also travels the same distance. For example, when magnet <NUM> travels <NUM> above the neutral position, the end of rectangular membrane <NUM> attached to magnet <NUM> also travels <NUM> in the same direction. Similarly, the frequency at which magnet <NUM> reciprocates up and down is the same frequency at which the end of rectangular membrane <NUM> that is coupled to magnet <NUM> travels the same distance. Preferably, the frequency is between <NUM> to <NUM>, though other frequencies may be achieved using the system described herein.

Accordingly, when blood is delivered to inlet channel <NUM> and around inflow separator <NUM>, it is propelled along both the top and bottom of rectangular membrane <NUM> and ultimately out of outlet <NUM>. The waves formed in the undulating rectangular membrane may be manipulated by changing the speed at which magnet <NUM> moves up and down as well as the distance magnet <NUM> moves up and down. The transfer of energy from the membrane to the blood is directed along the length of membrane <NUM> towards outlet <NUM>, and propels the blood along both sides of rectangular membrane <NUM>.

In <FIG> magnet <NUM> is moving upward. As magnet <NUM> moves upwards, the entrance into lower flow channel <NUM> between a bottom surface of magnet <NUM> and mounting structure <NUM> begins to increase in size while the entrance to upper flow channel <NUM> between an upper surface of magnet <NUM> and mounting structure <NUM> begins to simultaneously decrease in size, causing blood to fill lower flow channel <NUM> nearest magnet <NUM>. As magnet <NUM> is subsequently moved downward towards second electromagnet <NUM>, lower flow channel <NUM> begins to narrow near magnet <NUM> and continues to narrow as a wave-like deformations in membrane <NUM> are propagated toward outlet <NUM>. As the wave propagates across rectangular membrane <NUM>, blood in the lower flow channel <NUM> is propelled towards outlet <NUM>. Simultaneously, as magnet <NUM> moves down, the entrance to upper flow channel <NUM> begins to enlarge, allowing blood from inlet channel <NUM> to flow into this region. Subsequently, when magnet <NUM> is again thrust upwards, upper flow channel <NUM> begins to narrow near magnet <NUM>, causing wave-like deformations to propagate across membrane <NUM>, propelling blood towards outlet <NUM>. Preferably, the speed of the wave propagation is <NUM> to <NUM>/s, though other propagation speeds may be achieved using the system described herein.

By manipulating the waves formed in the undulating membrane by changing the frequency and amplitude at which magnet <NUM> moves up and down, the pressure gradient within upper flow channel <NUM> and lower flow channel <NUM> and ultimately the flow rate of the blood moving through implantable pump <NUM> may be adjusted. Appropriately controlling magnet <NUM> permits oxygen-rich blood to be effectively and safely pumped from the left atrium to the right subclavian artery and throughout the body as needed. While the pump described herein is described as pumping blood from the left atrium to the right subclavian artery, implantable pump <NUM> described herein could be used to pump blood from and to different areas, e.g. from the left ventricle to the aorta.

In addition to merely pumping blood from the left atrium to the subclavian artery, implantable pump <NUM> of the present invention may be operated to closely mimic physiologic pulsatility, without loss of pump efficiency. Pulsatility may be achieved nearly instantaneously by changing the frequency and amplitude at which magnet <NUM> moves, to create a desired flow output, or by ceasing movement of the magnet assembly <NUM> for a period time to create a period of low or no flow output. Unlike typical rotary pumps, which require a certain period of time to attain a set number of rotations per minute to achieve a desired fluid displacement and pulsatility, implantable pump <NUM> may achieve a desired flow output nearly instantaneously and similarly may cease output nearly instantaneously due to the very low inertia generated by the small moving mass of the moving components of the pump assembly. The ability to start and stop on-demand permits rapid changes in pressure and flow. Along with the frequency and amplitude, the duty cycle, defined by the percentage of time rectangular membrane <NUM> is excited over a set period of time, may be adjusted to achieve a desired flow output and pulsatility, without loss of pump efficiency. Even holding frequency and amplitude constant, flow rate may be altered by manipulating the duty cycle between <NUM> and <NUM>%.

In accordance with another aspect of the invention, controller <NUM> may be programmed by programmer <NUM> to operate at selected frequencies, amplitudes and duty cycles to achieve a wide range of physiologic flow rates and with physiologic pulsatilities. For example, programmer <NUM> may direct controller <NUM> to operate implantable pump <NUM> at a given frequency, amplitude and/or duty cycle during a period of time when a patient is typically sleeping and may direct controller <NUM> to operate implantable pump <NUM> at a different frequency, amplitude and or duty cycle during time periods when the patient is typically awake. Controller <NUM> or implantable pump <NUM> also may 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 certain discomfort or a physician determines that the parameters are not optimized, physician may alter one or more of at least frequency, amplitude and duty cycle to achieve the desired functionality. Alternatively, controller <NUM> or mobile device <NUM> may be configured to alter one or more of frequency, amplitude and duty cycle to suit the patient's needs.

Implantable pump <NUM> further may comprise one or more additional sensors for adjusting flow output and pulsatility according to the demand of the patient. Sensors may be incorporated into implantable pump <NUM> or alternatively or in addition to may be implanted elsewhere in or on the patient. The sensors preferably are in electrical communication with controller <NUM>, and may monitor operational parameters that measure the performance of implantable pump <NUM> or physiological sensors that measure physiological parameters of the patients such as heart rate or blood pressure. By using one or more physiological sensors, pulsatile flow may be synchronized with a cardiac cycle of the patient by monitoring blood pressure or muscle contractions, for example, and synchronizing the duty cycle according to the sensed output.

Controller <NUM> may compare physiological sensor measurements to current implantable pump output. If it is determined by analyzing sensor measurements that demand exceeds current output, frequency, amplitude and/or duty cycle may be automatically adjusted to meet current demand. Similarly, the controller may determine that current output exceeds demand and thus alter output by changing frequency, amplitude and/or duty cycle. Alternatively, or in addition to, when it is determined that demand exceeds current output, an alarm may sound from controller <NUM>. Similarly, operational measurements from operational sensors may be compared against predetermined thresholds and where measurements exceed predetermined thresholds or a malfunction is detected, an alarm may sound from controller <NUM>.

Implantable pump <NUM> is sized and shaped to produce physiological flow rates, pressure gradients and pulsatility at an operating point at which maximum efficiency is achieved. Preferably, implantable pump <NUM> is sized and shaped to achieve flow rates ranging from <NUM> to <NUM> liters per minute at pressure gradients lower than a threshold value associated with hemolysis. However, implantable pump <NUM> described herein may be sized and configured to achieve various other flow rates at pressure gradients lower than a threshold value associated with hemolysis. Also, to mimic a typical physiological pulse of <NUM> beats per minute, implantable pump <NUM> may pulse about once per second. To achieve such pulsatility, a duty cycle of <NUM>% may be utilized with an "on" period of <NUM> seconds and an "off" period of <NUM> seconds. For a given system, maximum efficiency at a specific operating frequency, amplitude and voltage may be achieved while producing a flow rate of <NUM> to <NUM> liters per minute at a duty cycle of <NUM>% by manipulating one or more of the shape and size of blood flow channels and gaps, elastic properties of spring system, mass of the moving parts, membrane geometries, and elastic properties and friction properties of the membrane. In this manner, implantable pump <NUM> may be designed to produce desirable outputs to partially support physiological circulation while continuing to function at optimum operating parameters.

By adjusting the duty cycle, implantable pump <NUM> may be configured to generate a wide range of output flows at physiological pressure gradients. For example, pump system <NUM> may be configured to produce <NUM> to <NUM> liters per minute at a duty cycle of <NUM>%, optimal operating frequency may be <NUM>. For this system, flow output may be increased to <NUM> liters per minute or decreased to <NUM> liters per minute, for example, by changing only the duty cycle. As duty cycle and frequency operate independent of one another, duty cycle may be manipulated between <NUM> and <NUM>% while leaving the frequency of <NUM> unaffected.

The implantable pump system described herein may be tuned to achieve partial-support flow rates and physiological pressure gradients and pulsatility while avoiding hemolysis and platelet activation by applying low to moderate shear forces on the blood, similar to those exerted by a healthy heart. The moving components are rigidly affixed to one another and do not incorporate any parts that would induce friction, such as mechanical bearings or gears. Inlet channel <NUM> and upper flow channel <NUM> and lower flow channel <NUM> are sized and configured to also avoid friction by sizing the channels and gaps such that clearances of at least <NUM> are maintained between all moving components. Similarly, magnet <NUM> is sized and configured to be separated by at least <NUM> from non-moving components such as mounting structure <NUM> to avoid friction.

Other embodiments of pump system <NUM> may include fewer or additional components or components having different shapes or sizes. For example, <FIG> illustrates an implantable housing <NUM>' that narrows toward outlet <NUM>'. In this configuration, the rectangular membrane may be disposed therein and similarly narrow as it nears outlet <NUM>'. In this embodiment, the narrowing of implantable housing <NUM>' may help direct the blood flow out of outlet <NUM>'.

Other embodiments may employ an electromagnetic actuator having magnets and electromagnetic portions different than those described in <FIG>. For example, <FIG> illustrates an alternative embodiment of the pump assembly. Pump assembly <NUM>', shown in <FIG>, includes electromagnetic assembly <NUM>', magnet assembly <NUM>', first support structure <NUM>, second support structure <NUM>, membrane holder <NUM> and rectangular membrane <NUM>. Membrane holder <NUM> is configured to be disposed within and mounted to implantable housing <NUM> using screws, welding or any other well-known technique appropriate for rigidly coupling membrane holder <NUM> to implantable housing <NUM>. Membrane holder <NUM> is configured to support electromagnetic assembly <NUM>' and rectangular membrane <NUM>.

First support structure <NUM> and second support structure <NUM> are also configured to be disposed within and mounted to implantable housing using any well-known technique such as screws or welding. First support structure <NUM> and second support structure <NUM> each may support a portion of magnet assembly <NUM>' having one or more positive permanent magnets and negative permanent magnets. Magnet assembly <NUM>' may be mounted to first support structure <NUM> and second support structure <NUM> such that a magnetic field is generated at a top end of first support structure <NUM> and second support structure <NUM> and a magnetic field having an opposite polarity is generated near a bottom end of first support structure <NUM> and second support structure <NUM>. First support structure <NUM> and second support structure <NUM> may be mounted to implantable housing <NUM> such that a gap exists between the two that is sufficiently large enough for electromagnetic assembly <NUM>' to fit between and move in a plane parallel to the gap.

Membrane holder <NUM> may be flexible and may permit electromagnetic assembly <NUM>' to move up toward the first magnetic field and down toward the second magnetic field. As electromagnetic assembly <NUM>' moves up and down, an end of membrane <NUM> coupled to electromagnetic assembly <NUM>' is also caused to move up and down. Also, as electromagnetic assembly <NUM>' moves up and down, membrane holder <NUM> is elastically deformed and applies a spring force is to electromagnetic assembly <NUM>' to return electromagnetic assembly <NUM>' to the neutral position where membrane holder <NUM> is not deformed.

As the end of rectangular membrane <NUM> moves up and down, wavelike deformations are propagated along membrane <NUM> toward outlet <NUM>, as described above. In this embodiment, current applied to electromagnetic assembly <NUM>' causes electromagnetic assembly <NUM>' to move up and down while magnet assembly <NUM>' stays stationary. Unlike the embodiment where magnet <NUM> moves, in the embodiment illustrated in <FIG>, electromagnetic assembly <NUM>' may be attracted to and thus move toward one magnetic field by inducing current in one direction, and conversely, may be attracted to and thus move in the other direction towards the other magnetic field, having an opposite polarity, by inducing current in the opposite direction.

Another embodiment of the electromagnetic actuator is illustrated in <FIG>. In <FIG>, an alternative system for propagating waves in the membrane is described. As is shown in <FIG>, this alternative system may include rectangular membrane <NUM>, first magnet <NUM>, first coil <NUM>, and first ferromagnetic casing <NUM> as well as second magnet <NUM>, second coil <NUM>, and second ferromagnetic casing <NUM>. First magnet <NUM> and second magnet <NUM> are connected by rod <NUM> which is also coupled to membrane <NUM>. First coil <NUM> and second coil <NUM> may be connected to controller <NUM> and/or battery <NUM>. Controller may induce, and alternate, current in first coil <NUM> and second coil <NUM> which causes first magnet <NUM> and second magnet <NUM> to move up and down in tandem. As first magnet <NUM> and second magnet <NUM> move up and down, rod <NUM> may be moved up and down causing the portion of membrane <NUM> connected to rod <NUM> to move up and down. In this manner, membrane <NUM> may be caused to undulate. Membrane <NUM> may vary in thickness as it moves from one end to another. The alternative electromagnetic actuator shown in <FIG> may be designed and configured to fit within pump housing <NUM> and function as a blood pump in the manner described herein.

Referring now to <FIG>, an electromechanical actuator embodiment is illustrated. The system shown in <FIG> includes rectangular membrane <NUM>, rod <NUM>, guide <NUM>, cam <NUM>, an assembly of coil <NUM>, rotating magnet <NUM>, the combination of <NUM> and <NUM> forming an asynchronous motor, and connector <NUM>. Coil <NUM> may be in electrical communication with controller <NUM> and/or battery <NUM> and may be energized to move in rotation magnet <NUM> on the same axis as coil <NUM>. Rotating magnet <NUM> may be connected to connector <NUM> which is connected to cam <NUM> at the other end. Membrane <NUM> is connected at one end to rod <NUM>. Rod <NUM> is connected to cam <NUM> at one end and is guided by guide <NUM> so that rod <NUM> is only free to move along its longitudinal axis. As rotating magnet <NUM> is caused by the magnetic field generated by coil assembly <NUM>, the movement of rotation of magnet <NUM> is transmitted by cam <NUM> via connector <NUM> to rod <NUM> which moves up and down its longitudinal axis. As rod <NUM> moves up and down its longitudinal axis, the end of membrane <NUM> that is connected to rod <NUM> moves up and down causing wave-like deformations to propagate along membrane <NUM>. The alternative electromechanical actuator shown in <FIG> may be designed and configured to fit within pump housing <NUM> and function as a blood pump in the manner described herein.

Referring now to <FIG>, implantable pump <NUM>, which may be used in system <NUM> in place of implantable pump <NUM>, is illustrated in greater detail. Implantable pump <NUM> includes pump housing <NUM> which is made of a biocompatible material, such as titanium, and is sized to be implanted within a patient's chest as described above. Pump housing <NUM> may be two or more pieces that fit together by, for example, threads or welding, to form fluid tight pump housing <NUM>. In one embodiment, pump housing <NUM> is sized and configured to have a length between <NUM>-<NUM>, a width between <NUM>-<NUM> and a height between <NUM>-<NUM>. However, pump housing <NUM> may have any other size suitable for pump assembly <NUM> to be disposed within pump housing <NUM>. Pump housing includes inlet <NUM> and outlet <NUM> through which blood may flow in and out, respectively. Pump also may include electrical port <NUM> to attach implantable pump <NUM> to cable <NUM>. Electrical port <NUM> may permit cable <NUM> to transverse pump housing <NUM> and connect to pump assembly <NUM> in a fluid tight manner. Cable <NUM> may deliver electrical wires from controller <NUM> and battery <NUM> to pump assembly <NUM>.

Referring to <FIG>, pump assembly <NUM> is illustrated in greater detail. Pump assembly <NUM> may include membrane assembly <NUM>, magnet assembly <NUM>, electromagnetic assembly <NUM>, fixation elements <NUM> and <NUM>, and funnel assembly <NUM>. Membrane assembly <NUM> may include mounting structure <NUM>, membrane holder <NUM> and rectangular membrane <NUM>. Electromagnetic assembly <NUM> includes first coil <NUM> and second coil <NUM> each having an electromagnetic winding. Magnet assembly <NUM> includes upper magnet unit <NUM> and a lower magnet unit <NUM>.

Pump assembly <NUM> is sized and configured to fit within pump housing <NUM>. Fixation elements <NUM> and <NUM>, mounting structure <NUM> and funnel assembly <NUM> may be mounted to pump housing <NUM> using any well-known fixation technique. For example, fixation elements <NUM> and <NUM>, mounting structure <NUM>, funnel assembly <NUM> may include threaded grooves that correspond to threaded grooves in pump housing <NUM> and may be coupled to pump-housing <NUM> using plurality of screws. Alternatively, fixation elements <NUM> and <NUM>, mounting structure <NUM>, funnel assembly <NUM> may be welded to pump housing <NUM>.

Referring now to <FIG>, an exploded view of pump assembly <NUM> is illustrated. As is shown in <FIG>, upper magnet unit <NUM> and lower magnet unit <NUM> may include a number of smaller magnets, or alternatively may include only a single magnet. As is also shown in <FIG>, both upper magnet unit <NUM> and lower magnet unit <NUM> may be rectangular in shape and may be sized and configured to be supported by funnel assembly <NUM>. Upper magnet unit <NUM> and lower magnet unit <NUM> also may be secured to pump housing <NUM> and may include a securing portion designed to secure upper magnet unit <NUM> and lower magnet unit <NUM> to pump housing <NUM>.

Funnel assembly <NUM> may include upper funnel <NUM> and lower funnel <NUM>, as is illustrated in <FIG>. Upper funnel <NUM> and lower funnel <NUM> may include a flanged portion for supporting upper magnet unit <NUM> and lower magnet unit <NUM>, respectively. Upper funnel <NUM> may have an upper surface secured to pump housing <NUM> and lower funnel <NUM> may have a lower surface secured to pump housing <NUM>. When lower funnel <NUM> and upper funnel <NUM> are secured to the pump housing, a gap exists between lower funnel <NUM> and upper funnel <NUM>, as is illustrated in <FIG>.

Between lower funnel <NUM> and upper funnel <NUM> rectangular membrane <NUM> is suspended and may extend the length of upper funnel <NUM> and lower funnel <NUM>. Posts <NUM> and <NUM> extend between upper funnel <NUM> and lower funnel <NUM> near a distal end of upper funnel <NUM> and lower funnel <NUM> adjacent to outlet <NUM> of pump housing <NUM>. Posts <NUM> and <NUM> are positioned in a parallel fashion and are separated a sufficient distance to permit fluid flow between them. Rectangular membrane <NUM> is connected to posts <NUM> and <NUM> at a distal end of rectangular membrane <NUM>. Rectangular membrane <NUM> may have two holes in the distal end of rectangular membrane <NUM> that are sized and configured to receive posts <NUM> and <NUM>. Posts <NUM> and <NUM> may further include connection elements that move freely along posts <NUM> and <NUM> and serve to anchor rectangular membrane <NUM> to posts <NUM> and <NUM>.

As is shown in <FIG> as well as <FIG>, membrane holder <NUM> is positioned at the distal end of rectangular membrane <NUM>. As is illustrated in <FIG>, membrane holder <NUM> is also positioned between upper magnet unit <NUM> and lower magnet unit <NUM>. Additionally, membrane holder <NUM> is positioned between first coil <NUM> and second coil <NUM>. Membrane holder <NUM> may be designed to couple to membrane clamp <NUM>. To secure rectangular membrane <NUM> to membrane holder <NUM>, a proximal end of rectangular membrane <NUM> may be placed over an end of membrane holder <NUM> designed to received rectangular membrane <NUM>. Subsequently, membrane clamp <NUM> may be placed over the portion of rectangular membrane <NUM> that is covering membrane holder <NUM> and clamped or otherwise secured to membrane holder <NUM>. Membrane clamp <NUM> may be designed to snap into membrane holder <NUM> or otherwise screw into membrane holder <NUM>. In this manner, rectangular membrane <NUM> may be secured to membrane holder <NUM>. Alternatively, rectangular membrane <NUM> may secured to membrane holder <NUM> without the use of membrane clamp <NUM> using a number of well-known securing techniques, e.g. epoxy, screws, etc. At a proximal end of membrane holder <NUM>, membrane holder <NUM> is secured to mounting structure <NUM>. As explained above, mounting structure <NUM> is secured to pump housing <NUM>.

First coil <NUM> and second coil <NUM> of electromagnetic assembly <NUM> may include one or more smaller metallic wires that may be wound into a coil, and may be in electrical communication with battery and/or controller via cable <NUM> connected via electrical port <NUM>. First coil <NUM> and second coil <NUM> are in electrical communication with one another and are electrically activated independently and may have separate wired connections to controller <NUM> and/or battery <NUM> via cable <NUM>. Current flow applied to first coil <NUM> and second coil <NUM> could be reversed depending on the operating parameters applied. The wires of first coil <NUM> and second coil <NUM> may be insulated to prevent shorting to adjacent conductive material.

First coil <NUM> and second coil <NUM> may include membrane holder receiving portions <NUM> for securing a portion of the distal end of membrane holder <NUM> to first coil <NUM> on one side and second coil <NUM> on the other side. In this manner, first coil <NUM> and second coil <NUM> are supported only by membrane holder <NUM> which is mounted on mounting structure <NUM>. The connection between first coil <NUM> and second coil <NUM> and membrane holder <NUM> may further include a spring system to reduce resonance effects. First coil <NUM> and second coil <NUM> are positioned relative to membrane holder <NUM> such that upper magnet unit <NUM> and lower magnet unit <NUM> are positioned between first coil <NUM> and second coil <NUM> but do touch coil <NUM> and second coil <NUM>. First coil <NUM> and second coil <NUM> may be sized such that upper funnel <NUM> and lower funnel <NUM> are positioned between first coil <NUM> and second coil <NUM> without touching first coil <NUM> and second coil <NUM>.

Fixation elements <NUM> and <NUM> may be secured to pump housing <NUM> such that first coil <NUM> and second coil <NUM> are positioned between fixation elements <NUM> and <NUM> without touching fixation elements <NUM> and <NUM>. Fixation elements <NUM> and <NUM> may have magnetic properties and thus may loop the magnet field created by magnet assembly <NUM> and otherwise contribute to the magnetic force generated. In this manner, first coil <NUM> is positioned between fixation element <NUM> on one side and on the other side magnet assembly <NUM>, membrane holder <NUM>, rectangular membrane <NUM> and funnel assembly <NUM>. Similarly, second coil <NUM> is positioned between fixation element <NUM> on one side and on the other side magnet assembly <NUM>, membrane holder <NUM>, rectangular membrane <NUM> and funnel assembly <NUM> on the other side. Also, in this configuration, rectangular membrane <NUM> is suspended within funnel assembly <NUM>, membrane holder <NUM> is suspended within magnet assembly <NUM> rectangular membrane <NUM> and membrane holder <NUM> are surrounded on either side by first coil <NUM> and second coil <NUM>.

Implantable pump housing <NUM>, fixation elements <NUM> and <NUM>, mounting structure <NUM>, and funnel assembly <NUM> may be comprised of titanium, stainless steel or any other rigid biocompatible material suitable for mounting pump assembly <NUM> to pump housing <NUM>. These components may be insulated and/or made of non-conductive material to reduce unwanted transmission of the electrical signal. Magnet assembly <NUM> may be comprised of one or more materials exhibiting magnetic properties such as iron, nickel, cobalt or various alloys. Where multiple magnets make up magnet assembly <NUM>, the magnets may be linked by metallic parts made of a high saturation alloy, such as Vacoflux. Mounting structure too may be made from Vacoflux. The one or more smaller metallic wires wound into a coil in electromagnetic assembly <NUM> may be made of copper or any other metal having appropriate electromagnetic properties.

Referring now to <FIG>, a portion of funnel assembly <NUM> is illustrated. The funnel portion illustrated may be either upper funnel <NUM> and lower funnel <NUM> as these units may be interchangeable. As is illustrated in <FIG>, the thickness of the funnel portion increases as it moves towards narrows funnel outlet <NUM>. As is also illustrated in <FIG>, the width of the flow channel creased by the flow channel narrows as it moves towards funnel outlet <NUM>. The funnel may include flanged portion <NUM> designed to support at least a portion of magnetic assembly <NUM> and secure at least a portion of magnetic assembly <NUM> to pump housing <NUM>. Upper funnel <NUM> and lower funnel <NUM> also may include threaded portions <NUM> that extend the through upper funnel <NUM> and lower funnel <NUM> or at least partway through and permit upper funnel <NUM> and lower funnel <NUM> to be secured to pump housing <NUM>.

Referring now to <FIG>, membrane holder <NUM> is illustrated. As is shown in these figures, membrane holder <NUM> may be generally rectangular having mounting potion <NUM> and membrane securing portion <NUM>. Mounting portion <NUM> is designed to be secured to mounting structure <NUM>. As is shown in <FIG>, at least membrane securing portion <NUM> is designed to be flexible. As such, membrane securing portion <NUM> may flex up and down relative to mounting portion <NUM>. Membrane holder <NUM>, including at least membrane securing portion <NUM>, may have elastic properties which exhibits a spring force when membrane securing portion <NUM> is deflected relative to mounting potion <NUM>. While, membrane securing portion <NUM> may flex when deformed up and down relative mounting portion <NUM>, membrane securing portion <NUM> may rigidly resist movement along any other axis, e.g., tilt or twist movements. Membrane holder <NUM> may be made from any metal or material having the properties just described.

In one embodiment, membrane holder <NUM> and/or membrane clamp <NUM> may exhibit electromagnetic properties. For example, membrane holder <NUM> and/or membrane clamp <NUM> may be in electrical communication with electromagnetic assembly <NUM>. As such when electromagnetic assembly <NUM> is electrically activated, membrane holder <NUM> and/or membrane clamp <NUM> may too become electrically activated and thus generate a magnetic field due to their electromagnetic properties. In generating an electromagnetic field, membrane holder <NUM> and/or membrane clamp <NUM> may become attracted to either upper magnet unit <NUM> or lower magnet unit <NUM>.

Referring now to <FIG>, rectangular membranes similar to those described above in <FIG> are illustrated. Thus, the description of the rectangular membranes in <FIG> can be referred to above. In general, rectangular membrane <NUM> may take a general thin rectangular shape. In a preferred embodiment, rectangular membrane <NUM> has a thin, planar shape and is made of an elastomer having elastic properties and good durability. Rectangular membrane <NUM> may have a uniform thickness from one end to the other. As yet a further alternative, rectangular membrane <NUM> may vary in thickness and exhibit more complex geometries. For example, rectangular membrane <NUM> may have a reduced thickness as the membrane extends from one end to the other. Alternatively, or in addition to, rectangular membrane <NUM> may incorporate metallic elements such as a spring to enhance the spring force of the membrane in a direction normal to plane of the membrane. In yet another embodiment, rectangular membrane <NUM> may be pre-formed with an undulating shape.

As is illustrated in <FIG>, rectangular membrane <NUM> may have two post receiving portions <NUM> and <NUM>. Post receiving portions <NUM> and <NUM> may have a diameter slightly larger than that of posts <NUM> and <NUM>. Also, as shown in <FIG>, rectangular membrane <NUM> may have extended portions <NUM> and <NUM>. Extended portions <NUM> and <NUM> may permit fluid to more freely escape out of outlet <NUM> of implantable pump <NUM>. Alternatively, in <FIG>, rectangular membrane <NUM>' may extend the entire length of the membrane without any extended portions. In yet another alternative, as shown in <FIG>, rectangular membrane <NUM>" may not include the post receiving portions. This may permit the distal end of rectangular membrane <NUM>" nearest outlet <NUM> to move more freely.

Referring now to <FIG>, sectional views of non-claimed examples of implantable pump <NUM> are illustrated. In <FIG>, rectangular membrane <NUM> and membrane holder <NUM> are seen suspended between upper funnel <NUM> and upper magnet unit <NUM> above, and lower funnel <NUM> and lower magnet unit <NUM> below. Rectangular membrane <NUM> is shown being held in tension between membrane holder <NUM> and posts <NUM> and <NUM>. As is also shown in <FIG>, second coil <NUM> is suspended within implantable pump housing <NUM> by membrane holder <NUM> which is secured in a cantilevered configuration by mounting structure <NUM>.

From <FIG> it is clear that a flow channel exists between inlet <NUM> and outlet <NUM>. Specifically, blood may flow through inlet <NUM>, over and around mounting structure <NUM>, and then flow toward outlet <NUM> between upper magnet unit <NUM> and a top surface of membrane holder <NUM> and membrane <NUM> as well as between lower magnet unit <NUM> and a bottom surface of membrane holder <NUM> and membrane <NUM>. As the blood nears the outlet, blood may then flow between a bottom surface of upper funnel <NUM> and a top surface of membrane <NUM> as well as between a top surface of lower funnel <NUM> and a bottom surface of membrane <NUM>. As blood flows through funnel assembly <NUM>, the flow channel begins to narrow.

Referring now to <FIG>, a sectional view along an orthogonal plane from that shown in <FIG> is provided. As just described, blood may enter from inlet <NUM> and travel along membrane holder <NUM> and rectangular membrane <NUM>. As is shown in <FIG>, blood may flow in the space between first coil <NUM> and second coil <NUM> and may even flow between first coil <NUM> and second coil <NUM> and fixation elements <NUM> and <NUM>, respectively. As will be described in greater detail below, first coil <NUM> and second coil <NUM> and fixation elements, membrane holder <NUM> and rectangular membrane <NUM> all may move relative to pump housing <NUM>. Conversely, mounting structure <NUM>, magnet assembly <NUM>, fixation elements <NUM> and <NUM>, and funnel assembly <NUM> remain stationary relative to pump housing <NUM>. Thus, in accordance with one aspect of the present invention, the implantable pump described herein avoids thrombus formation by placing all moving parts directly within the primary flow path, thereby reducing the risk of flow stagnation. Flow stagnation is further avoided by configuring all gaps in the flow path to be no less than <NUM> and also by eliminating secondary flow paths that may experience significantly slower flow rates.

Referring now to <FIG>, implantable pump of non-claimed examples may be activated to pump blood from inlet <NUM> to outlet <NUM> by moving first coil <NUM> and second coil <NUM> up and down relative to pump housing <NUM>. Constrained by only membrane holder <NUM>, first coil <NUM> and second coil <NUM> may move up and down between membrane holder <NUM>, rectangular membrane <NUM>, magnet assembly <NUM> and funnel assembly <NUM> on one side and fixation elements <NUM> and <NUM> on the other. To move first coil <NUM> and second coil <NUM> up, current may be applied to first coil <NUM> and second coil <NUM> such that first coil <NUM> and second coil <NUM> generate a magnetic field that causes first coil <NUM> and second coil <NUM> to move toward upper magnet unit <NUM>. Conversely, to move first coil <NUM> and second coil <NUM> down, current may be applied to first coil <NUM> and second coil <NUM> such that first coil <NUM> and second coil <NUM> generate an electric field that causes first coil <NUM> and second coil <NUM> to move toward lower magnet unit <NUM>.

Upper magnet unit <NUM> and lower magnet unit <NUM> may have opposite polarities such that when current is applied in one direction through first coil <NUM> and second coil <NUM>, first coil <NUM> and second coil <NUM> are attracted to upper magnet unit <NUM>, but when current is applied to first coil <NUM> and second coil <NUM> in the reverse direction, first coil <NUM> and second coil <NUM> are attracted to lower magnet unit <NUM>.

In <FIG>, current is flowing in first coil <NUM> and second coil <NUM> such that first coil <NUM> and second coil <NUM> are attracted to upper magnet unit <NUM>. First coil <NUM> and second coil <NUM> may be activated by controller <NUM> by applying an electrical signal from battery <NUM> to first coil <NUM> and second coil <NUM>, thus inducing current in the first coil <NUM> and second coil <NUM> and generating a magnetic field surrounding first coil <NUM> and second coil <NUM>. As membrane holder <NUM> includes a flexible portion to which first coil <NUM> and second coil <NUM> are secured to and suspended by, first coil <NUM> and second coil <NUM> are free to move up toward upper magnet unit <NUM>. Similarly, should the direction of current be reversed in first coil <NUM> and second coil <NUM>, first coil <NUM> and second coil <NUM> would be attracted to lower magnet unit <NUM> and thus move down toward lower magnet unit <NUM>.

As membrane holder <NUM> exhibits a spring force when elastically deformed in a direction normal to a longitudinal plane of membrane holder <NUM>, when first coil <NUM> and second coil <NUM> move up toward upper magnet unit <NUM>, membrane holder <NUM> exerts a downward spring force on first coil <NUM> and second coil <NUM> toward the neutral position. Similarly, when first coil <NUM> and second coil <NUM> move downward toward lower magnet unit <NUM>, membrane holder <NUM> exerts an upward spring force on first coil <NUM> and second coil <NUM> toward the neutral position. The further first coil <NUM> and second coil <NUM> move from the undeflected neutral position, the greater the spring force applied to first coil <NUM> and second coil <NUM>.

By manipulating the timing and intensity of the electrical signals applied to electromagnetic assembly <NUM>, the frequency at which electromagnetic assembly <NUM> moves up and down may be altered. For example, by alternating the current induced in the electromagnetic assembly <NUM> more frequently, electromagnetic assembly <NUM> may be caused to cycle up and down more times in a given period. By increasing the voltage applied, the electromagnetic assembly <NUM> may be deflected at a faster rate and caused to travel longer distances.

As first coil <NUM> and second coil <NUM> are rigidly coupled to an end of membrane holder <NUM> and rectangular membrane <NUM> is also coupled at the same end of membrane holder <NUM>, movement of first coil <NUM> and second coil <NUM> is applied to the end of rectangular membrane <NUM>. <FIG> and 125B illustrate movement by first coil <NUM> and second coil <NUM> being applied to rectangular membrane <NUM>. As is shown in <FIG>, a current has been induced in first coil <NUM> and second coil <NUM> such that first coil <NUM> and second coil <NUM> are attracted to upper magnet unit <NUM>. The movement of first coil <NUM> and second coil <NUM> has caused membrane securing portion <NUM> to move upward with first coil <NUM> and second coil <NUM>. In <FIG>, the deformation in membrane holder <NUM> can clearly be seen. As can also be seen, rectangular membrane <NUM> has traveled upward with membrane securing portion <NUM>.

As rectangular membrane <NUM> is attached to the same portion of membrane holder <NUM> as first coil <NUM> and second coil <NUM>, when first coil <NUM> and second coil <NUM> travel a certain distance upward or downward, the end of rectangular membrane <NUM> attached to membrane holder <NUM> also travels the same distance. For example, when first coil <NUM> and second coil <NUM> travel <NUM> above the neutral position of membrane holder <NUM>, the end of rectangular membrane <NUM> attached to membrane holder <NUM> also travels <NUM> in the same direction. Similarly, the frequency at which first coil <NUM> and second coil <NUM> reciprocates up and down is the same frequency at which rectangular membrane <NUM> travels the same distance. Preferably, the frequency is between <NUM> to <NUM>, though other frequencies may be achieved using the system described herein.

Referring now to <FIG>, and as is illustrated in <FIG> and <FIG> and described above, blood enters implantable pump <NUM> from inlet cannula <NUM> extending into the left atrium and flows into inlet <NUM> directly into delivery channel <NUM>. As the blood moves toward outlet <NUM> it is directed through gap <NUM> between upper magnet unit <NUM> and lower magnet unit <NUM> and then into gap <NUM> between upper funnel <NUM> and lower funnel <NUM>. By directing blood from delivery channel <NUM> to gap <NUM> blood is delivered to rectangular membrane <NUM>. By inducing alternating current to first coil <NUM> and second coil <NUM>, membrane <NUM> may be undulated between gaps <NUM> and <NUM> to induce wavelike formations in rectangular membrane <NUM> that moves from the edge of rectangular membrane <NUM> coupled to membrane holder <NUM> towards outlet <NUM>. Accordingly, when blood is delivered to rectangular membrane <NUM> from delivery channel <NUM>, it is propelled along both the top and bottom of rectangular membrane <NUM> and ultimately out of outlet <NUM>. The waves formed in the undulating rectangular membrane may be manipulated by changing the speed at which first coil <NUM> and second coil <NUM> move up and down as well as the distance first coil <NUM> and second coil <NUM> move up and down. The transfer of energy from the membrane to the blood is directed along the length of the membrane towards outlet <NUM>, and propels the blood along both sides of rectangular membrane <NUM>.

<FIG> shows that when membrane securing portion <NUM> moves upward, the lower portion of gap <NUM> below membrane holder <NUM> and rectangular membrane <NUM> expands, causing blood to fill the lower portion of gap <NUM>. As membrane securing portion <NUM> moves downward, the lower portion of gap <NUM> begins to narrow toward outlet <NUM>, causing wave-like deformations to translate across the membrane. As the wave propagates across rectangular membrane <NUM>, blood in the lower portion of gap <NUM> is propelled towards gap <NUM> and ultimately out of implantable pump <NUM>. As blood moves toward outlet <NUM> within gap <NUM>, gap <NUM> narrows accelerating the blood towards the outlet. Simultaneously, as membrane securing portion <NUM> moves downwards, the upper portion of gap <NUM> above the top surface of rectangular membrane <NUM> and membrane holder <NUM>, begins to enlarge, allowing blood from delivery channel <NUM> to flow into this region. Subsequently, when membrane securing portion <NUM> is again thrust upwards, the upper portion of gap <NUM> begins to narrow, causing wave-like deformations to propagate across the membrane, propelling blood towards outlet <NUM>. Preferably, the speed of the wave propagation is <NUM> to <NUM>/s, though other propagation speeds may be achieved using the system described herein.

By manipulating the waves formed in the undulating membrane by changing the frequency and amplitude at which membrane securing portion <NUM> moves up and down, the pressure gradient within gap <NUM> and gap <NUM> and ultimately the flow rate of the blood moving through implantable pump <NUM> may be adjusted. Appropriately controlling the membrane securing portion <NUM> permits oxygen-rich blood to be effectively and safely pumped from the left atrium to the right subclavian artery and throughout the body as needed. While the pump described herein is described as pumping blood from the left atrium to the right subclavian artery, the implantable pump described herein could be used to pump blood from and to different areas, e.g. from the left ventricle to the aorta.

In addition to merely pumping blood from the left atrium to the subclavian artery, implantable pump <NUM> of the present invention may be operated to closely mimic physiologic pulsatility, without loss of pump efficiency. Pulsatility may be achieved nearly instantaneously by changing the frequency and amplitude at which membrane securing portion <NUM> moves, to create a desired flow output, or by ceasing movement of the electromagnetic assembly <NUM> for a period time to create a period of low or no flow output. Unlike typical rotary pumps, which require a certain period of time to attain a set number of rotations per minute to achieve a desired fluid displacement and pulsatility, implantable pump <NUM> may achieve a desired flow output nearly instantaneously and similarly may cease output nearly instantaneously due to the very low inertia generated by the small moving mass of the moving components of the pump assembly. The ability to start and stop on-demand permits rapid changes in pressure and flow. Along with the frequency and amplitude, the duty cycle, defined by the percentage of time rectangular membrane <NUM> is excited over a set period of time, may be adjusted to achieve a desired flow output and pulsatility, without loss of pump efficiency. Even holding frequency and amplitude constant, flow rate may be altered by manipulating the duty cycle between <NUM> and <NUM>%.

Implantable pump <NUM> is sized and shaped to produce physiological flow rates, pressure gradients and pulsatility at an operating point at which maximum efficiency is achieved. Preferably, implantable pump <NUM> is sized and shaped to achieve flow rates ranging from <NUM> to <NUM> liters per minute at pressure gradients lower than a threshold value associated with hemolysis. However, implantable pump <NUM> described herein may be sized and configured to achieve various other flow rates at pressure gradients lower than a threshold value associated with hemolysis. Also, to mimic a typical physiological pulse of <NUM> beats per minute, implantable pump <NUM> may pulse about once per second. To achieve such pulsatility, a duty cycle of <NUM>% may be utilized with an "on" period of <NUM> seconds and an "off" period of <NUM> seconds. For a given system, maximum efficiency at a specific operating frequency, amplitude and voltage may be achieved while producing a flow rate of <NUM> to <NUM> liters per minute at a duty cycle of <NUM>% by manipulating one or more of the shape and size of blood flow channels and gaps, elastic properties of the membrane holder, mass of the moving parts, membrane geometries, and elastic properties and friction properties of the membrane. In this manner, implantable pump <NUM> may be designed to produce desirable outputs to partially support physiological circulation while continuing to function at optimum operating parameters.

The implantable pump system described herein may be tuned to achieve partial-support flow rates and physiological pressure gradients and pulsatility while avoiding hemolysis and platelet activation by applying low to moderate shear forces on the blood, similar to those exerted by a healthy heart. The moving components are rigidly affixed to one another and do not incorporate any parts that would induce friction, such as mechanical bearings or gears. Delivery channel <NUM> and gaps <NUM> and <NUM> are sized and configured to also avoid friction by sizing the channels and gaps such that clearances of at least <NUM> are maintained between all moving components. Similarly, first electromagnet <NUM> and second electromagnet <NUM> and membrane holder <NUM> are sized and configured to be separated by at least <NUM> from non-moving components to avoid friction.

Other non-claimed examples of pump system <NUM> may include fewer or additional components. For example, <FIG> illustrates an alternative example wherein pump assembly <NUM>' includes electromagnetic assembly <NUM>' having only one electromagnet positioned between magnet assembly <NUM>'. Magnet assembly <NUM>' has an upper magnet unit with a gap in the middle and a lower magnet unit with a gap in the middle. Pump assembly <NUM>' also includes modified membrane holder <NUM>' which is coupled to mounting structure <NUM> at a proximal end, coupled to the electromagnetic assembly <NUM>' at a mid-section and coupled to rectangular membrane <NUM> at a distal end. As electromagnetic assembly <NUM>' is electrically activated and attracted to lower magnet unit and upper magnet unit of magnet assembly <NUM>', electromagnetic assembly <NUM>' moves up and down through the gaps in magnet assembly <NUM>'. Like in the embodiment described above, as modified membrane holder <NUM>' moves up and down with electromagnetic assembly <NUM>', the end of rectangular membrane <NUM> coupled to modified membrane holder <NUM>' also travels up and down, thereby deforming rectangular membrane <NUM> and propagating wavelike deformations toward outlet <NUM>. In this example, though the displacement of rectangular membrane <NUM> is proportional to the displacement of electromagnetic assembly <NUM>', the displacement may not be the same depending on the design of modified membrane holder <NUM>'.

Other non-claimed examples may employ an electromagnetic actuator having magnets and electromagnetic portions different than those described in <FIG>. For example, in <FIG> an alternative system for propagating waves in the membrane is described. As is shown in <FIG>, this alternative system may include membrane <NUM>, first magnet <NUM>, first coil <NUM>, and first ferromagnetic casing <NUM> as well as second magnet <NUM>, second coil <NUM>, and second ferromagnetic casing <NUM>. First magnet <NUM> and second magnet <NUM> are connected by rod <NUM> which is also coupled to membrane <NUM>. First coil <NUM> and second coil <NUM> may be connected to controller <NUM> and/or battery <NUM>. Controller may induce, and alternate, current in first coil <NUM> and second coil <NUM> which causes first magnet <NUM> and second magnet <NUM> to move up and down in tandem. As first magnet <NUM> and second magnet <NUM> move up and down, rod <NUM> may be moved up and down causing the portion of membrane <NUM> connected to rod <NUM> to move up and down. In this manner, membrane <NUM> may be caused to undulate. Membrane <NUM> may vary in thickness as it moves from one end to another. The alternative electromagnetic actuator shown in <FIG> may be designed and configured to fit within pump housing <NUM> and function as a blood pump in the manner described herein.

Referring now to <FIG>, another electromagnetic actuator non-claimed example is illustrated. The system shown in <FIG> includes membrane <NUM>, bar magnet <NUM>, first coil <NUM>, second coil <NUM>, posts <NUM> and ferromagnetic housing <NUM>. In this embodiment, first coil <NUM> and second coil <NUM> may be in communication with controller <NUM> and/or battery <NUM>. First coil <NUM> and second coil <NUM> may be designed to receive an electrical signal that attracts bar magnet <NUM>. First coil <NUM> and second coil <NUM> also may be designed to repel bar magnet <NUM>. For example, first coil <NUM> may receive an electrical signal that causes first coil <NUM> to attract bar magnet <NUM> while at the same time, second coil <NUM> may receive an electrical signal that causes second coil <NUM> to repel bar magnet <NUM>. By alternating the current applied to first coil <NUM> and second coil <NUM>, bar magnet <NUM> is caused to move up and down along posts <NUM> towards and away from first coil <NUM> and second coil <NUM>. Bar magnet <NUM> may be coupled to membrane <NUM> along the perimeter of one end of membrane <NUM>. As bar magnet <NUM> moves up and down posts <NUM>, the end of membrane <NUM> coupled to bar magnet <NUM> may move up and down causing wave-like deformations that propagate along membrane <NUM>. The alternative electromagnetic actuator shown in <FIG> may be designed and configured to fit within pump housing <NUM> and function as a blood pump in the manner described herein.

Referring now to <FIG>, another electromechanical actuator non-claimed example is illustrated. The system shown in <FIG> includes membrane <NUM>, rod <NUM>, guide <NUM>, cam <NUM>, an assembly of coil <NUM>, rotating magnet <NUM>, the combination of <NUM> and <NUM> forming an asynchronous motor, and connector <NUM>. Coil <NUM> may be in electrical communication with controller <NUM> and/or battery <NUM> and may be energized to move in rotation magnet <NUM> on the same axis as coil <NUM>. Rotating magnet <NUM> may be connected to connector <NUM> which is connected to cam <NUM> at the other end. Membrane <NUM> is connected at one end to rod <NUM>. Rod <NUM> is connected to cam <NUM> at one end and is guided by guide <NUM> so that rod <NUM> is only free to move along its longitudinal axis. As rotating magnet <NUM> is caused to rotate by the magnetic field generated by coil assembly <NUM>, the movement of rotating magnet <NUM> is transmitted by cam <NUM> via connector <NUM> to rod <NUM> which moves up and down its longitudinal axis. As rod <NUM> moves up and down its longitudinal axis, the end of membrane <NUM> that is connected to rod <NUM> moves up and down causing wave-like deformations to propagate along membrane <NUM>. The alternative electromechanical actuator shown in <FIG> may be designed and configured to fit within pump housing <NUM> and function as a blood pump in the manner described herein.

Referring now to <FIG>, various configurations for energizing implantable pump <NUM> or <NUM> described above are provided. As shown in <FIG>, in a non-claimed example, controller <NUM> includes output port <NUM> which is electrically coupled to cable <NUM> as described above, which in turn is coupled to implantable pump <NUM> or <NUM>. Controller <NUM> also includes power connector <NUM>, which may be electrically coupled to a battery, an extension port electrically coupled to a battery, or an AC/DC power supply. For example, power connector <NUM> may be male, while the connector of the corresponding battery or extension port is female.

In one non-claimed example, as shown in <FIG>, controller <NUM> includes two power connectors, e.g., first power connector <NUM> and second power connector <NUM>. As described above, first power connector <NUM> may be electrically coupled to a first battery, a first extension port electrically coupled to a first battery, or a first AC/DC power supply, and second power connector <NUM> may be electrically coupled to a second battery, a second extension port electrically coupled to a second battery, or a second AC/DC power supply. In this embodiment, first power connector <NUM> and second power connector <NUM> may both be male. In addition, controller <NUM> includes circuitry for switching between power sources such that energy is selectively transmitted to controller <NUM> from at least one of the first or second battery/power supply. For example, the circuitry may switch between a first and second battery intermittently, or after the remaining power level of one of the batteries reaches a predetermined threshold.

Referring now to <FIG>, configurations are illustrated in non-claimed examples wherein controller <NUM> is directly electrically coupled to battery <NUM>, such that controller <NUM> and battery <NUM> may be worn by the patient together, e.g., via a purse, shoulder bag, or holster. As shown in <FIG>, controller <NUM> of <FIG> may be electrically coupled to battery <NUM> via power connector <NUM>, wherein power connector <NUM> is male and battery <NUM> has a corresponding female connector. For example, <FIG> illustrates controller <NUM> electrically coupled to battery <NUM>, wherein battery <NUM> has a smaller size, and therefore lower capacity, and <FIG> illustrates controller <NUM> electrically coupled to battery <NUM>, wherein battery <NUM> has a larger size, and therefore higher capacity. As will be understood by a person of ordinary skill in the art, battery <NUM> may have various sizes depending on the need of the patient.

Referring now to <FIG>, configurations are illustrated in non-claimed examples wherein controller <NUM> is remotely electrically coupled to battery <NUM>, such that the weight and volume of controller <NUM> and battery <NUM> are distributed and may be worn by the patient separately, e.g., via a belt or a vest. As shown in <FIG>, cable <NUM>, which electrically couples controller <NUM> to battery <NUM>, is electrically coupled to first power connector port <NUM> via strain relief <NUM>, which is a hardwired junction between cable <NUM> and first power connector port <NUM>. Power connector port <NUM> includes power connector <NUM>, which may be electrically coupled to a battery. For example, power connector <NUM> may be male, while the connector of the corresponding battery is female.

As shown in <FIG>, controller <NUM> may be remotely electrically coupled to battery <NUM> via cable <NUM>. Cable <NUM> is electrically coupled at one end to controller <NUM> via second power connector port <NUM> and strain relief <NUM>, which is a hardwired junction between cable <NUM> and second power connector port <NUM>, and electrically coupled at another end to battery <NUM> via first connector port <NUM> and strain relief <NUM>. For example, power connector <NUM> of controller <NUM> may be male while the connector of corresponding second power connector port <NUM> is female, and power connector <NUM> of first power connector port <NUM> may be male while the connector of corresponding battery <NUM> is female.

In one non-claimed example, as shown in <FIG>, controller <NUM> may be remotely electrically coupled to multiple batteries, e.g., battery 4A and battery 4B, via a single second power connector port <NUM>. As shown in <FIG>, second power connector port <NUM> includes first strain relief 215A and second strain relief 215B, such that controller <NUM> is remotely electrically coupled to battery 4A via cable 214A and remotely electrically coupled to battery 4B via cable 214B. Specifically, cable 214A is electrically coupled at one end to controller <NUM> via second power connector port <NUM> and first strain relief 215A, and electrically coupled at another end to battery 4A via first connector port 205A and strain relief 206A, and cable 214B is electrically coupled at one end to controller <NUM> via second power connector port <NUM> and second strain relief 215B, and electrically coupled at another end to battery 4B via first connector port 205B and strain relief 206B. In this embodiment, controller <NUM> may include circuitry for switching between battery 4A and battery 4B such that energy is selectively transmitted to controller <NUM> from at least one of battery 4A and battery 4B. For example, the circuitry may switch between battery 4A and battery 4B intermittently, or after the remaining power level of one of the batteries reaches a predetermined threshold. Alternatively, controller <NUM> may receive energy from battery 4A and battery 4B simultaneously.

In another non-claimed example, as shown in <FIG>, controller <NUM> is electrically coupled to AC/DC power supply <NUM>, which may be plugged into an electrical outlet via AC plug <NUM>, e.g., when the patient is resting bedside. Specifically, AC/DC power supply <NUM> is electrically coupled to controller <NUM> via cable <NUM>, such that cable <NUM> is electrically coupled at one end to controller <NUM> via second power connector port <NUM> and strain relief <NUM>, and electrically coupled at another end to AC/DC power supply <NUM> via first power supply port <NUM>. In addition, AC/DC power supply <NUM> is electrically coupled to plug <NUM> via cable <NUM> and second power supply port <NUM>.

Controller <NUM> may include an internal battery, such that the internal battery powers controller <NUM> and implantable pump <NUM> or <NUM> during the time required for battery <NUM> to be replaced and/or recharged. Accordingly, controller <NUM> may include circuitry for switching between power sources such that energy is transmitted to controller <NUM> from the internal battery while battery <NUM> is disconnected from controller <NUM>, and from battery <NUM> when battery <NUM> is electrically coupled to controller <NUM>. In addition, the circuitry may allow battery <NUM> to charge the internal battery while also energizing implantable pump <NUM> or <NUM> until the internal battery is recharged to a desired amount, at which point the circuitry allows battery <NUM> to solely energize implantable pump <NUM> or <NUM>. Similarly, when controller <NUM> is electrically coupled to AC/DC power supply <NUM>, the circuitry may allow AC/DC power supply <NUM> to charge the internal battery while also energizing implantable pump <NUM> or <NUM> until the internal battery is recharged to a desired amount, at which point the circuitry allows AC/DC power supply <NUM> to solely energize implantable pump <NUM> or <NUM>.

Claim 1:
An implantable blood pump (<NUM>, <NUM>) for use in a partial-support assist device, comprising:
a housing (<NUM>, <NUM>', <NUM>) having an inlet (<NUM>, <NUM>) and an outlet (<NUM>, <NUM>', <NUM>), the housing configured to be implanted within a patient;
a rectangular membrane (<NUM>, <NUM>', <NUM>", <NUM>"', <NUM>, <NUM>, <NUM>, <NUM>', <NUM>", <NUM>, <NUM>, <NUM>) disposed within the housing;
a magnet assembly (<NUM>, <NUM>', <NUM>, <NUM>') disposed within the housing and comprising one or more magnets (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>); and
an electromagnetic assembly (<NUM>, <NUM>', <NUM>, <NUM>') disposed within the housing, the electromagnetic assembly configured to generate, when electrically activated, a magnetic field applied to the one or more magnets to induce wave-like deformation of the rectangular membrane, thereby pumping blood from the inlet, along the rectangular membrane, and out the outlet,
wherein the electromagnetic assembly comprises a first electromagnet portion (<NUM>, <NUM>, <NUM>, <NUM>) and a second electromagnet portion (<NUM>, <NUM>, <NUM>, <NUM>),
wherein the first electromagnet portion and the second electromagnet portion are electrically activated independently,
wherein the magnet assembly is disposed between the first electromagnet portion and the second electromagnet portion.