Abstract: A system for generating a blood circulation in at least part of an organ of a vertebrate, including a first artificial cavity and a second artificial cavity. The cavities each include a flexible membrane capable of beating under the action of a gas. Each of the membranes separate in a sealed manner a blood circulation chamber and a chamber containing the gas. The system also includes: a first low pressure gas buffer reservoir; a second high-pressure gas buffer reservoir; a gas distribution; and a pneumatic pump.

Abstract: A ventricular assist device is disclosed. The ventricular assist device may include a centrifugal pump and a controller. The controller may be configured to cause the centrifugal pump to operate at a first speed above a predetermined flow rate. The controller may also be configured to cause the centrifugal pump to operate at a second speed below the predetermined flow rate, wherein the predetermined flowrate is indicative of a crossover point between systole and diastole phases of a person's cardiac cycle.

Abstract: An assembly with a blood pump and a control unit to control the flow rate at the blood pump includes a device that is designed to deliver a parameter of the breathing cycle or a parameter associated with the breathing cycle. In this way, it is also made possible for a parameter that correlates to the breathing cycle to be used to control the blood pump, in order to proactively prevent problems associated with the drainage.

Abstract: A mechanical circulatory assist system includes a continuous-flow pump and a controller. The pump is implantable to assist blood flow from the left ventricle to the aorta The controller is operable to control a rotation speed of the pump over an operational cycle. The operational cycle includes a first segment over which the ventricular assist device is operated at first rotation speed, a second segment over which the rotation speed of the ventricular assist device is decreased from the first rotation speed to a second rotation speed, a third segment over which the ventricular assist device is operated at the second rotation speed, and a fourth segment over which the rotation speed of the ventricular assist device is increased from the second rotation speed. A contraction of the left ventricle that opens and closes the native aortic valve occurs during the third segment.

Abstract: The present disclosure provides for a method, control device, and implantable system, for acquiring a plurality of flow rate data points over time, each data point indicative of a flow rate of blood through the pump, calculating, based on the plurality of acquired flow rate data points, a value characterizing one or more features of a waveform formed from the plurality of flow rate data points; and determining, based on the value, the presence or absence of a suction condition in the pump.

Abstract: Methods and apparatus for estimating flow rate in a blood circulation assist system employing impeller eccentricity. A method includes magnetically rotating an impeller within a blood flow channel of a blood pump. The impeller is levitated within the blood flow channel transverse to the impeller axis of rotation. A rotational speed for the impeller is determined. At least one impeller transverse position parameter is determined. The at least one impeller transverse position parameter is based on at least one of (1) an amount of a bearing current that is used to levitate the impeller transverse to the impeller axis of rotation, and (2) a position of the impeller within the blood flow channel transverse to the impeller axis of rotation. A flow rate of blood pumped by the blood pump is estimated based on the impeller rotational speed and the at least one impeller transverse position parameter.

Abstract: A system and method for detecting and mitigating a suction condition are disclosed. The method may include estimating a flow waveform of the pump, identifying pulses in the flow waveform, determining a negative flow based on a valid identification of a pulse, and evaluating a characteristic of the pulse for an existence of a suction condition. In various embodiments, a suction marker is located based on a minimum in a diastolic phase, and the suction marker location is used to identify a probability of a suction condition. A speed of the pump may be adjusted to mitigate the suction condition. A system and method for estimating flow is further disclosed. The method may include interpolating data sets defining pump power to flow for various pump speed values.

Abstract: The flow rate of blood in an implantable blood pump is determined at least in part based on a parameter related to thrust on the rotor of the pump. The parameter may be a parameter related to displacement of the rotor along its axis, such as a function of the back electromotive force generated in one or more coils of the stator. The back electromotive force may be measured during open-phase periods of a particular coil or set of coils, during which no power is applied to the coil or set of coils by the motor drive circuit. The parameter related to thrust may be used in conjunction with the speed of rotation of the rotor, the magnitude of current supplied to the rotor, or both to determine the flow rate. The pump may be controlled responsive to the determined flow rate.

Abstract: Disclosed herein are systems and methods for an implantable device comprising a ferromagnetic mass at least partially disposed near a coil, said coil formed of electrically conducting material and having electrical leads, a resonator circuit coupled to the leads and operable to resonate on application of energy from said leads. Some embodiments include an antenna coupled to said resonator circuit, wherein when either the ferromagnetic mass or the coil moves, power is supplied to the resonator circuit. In certain embodiments the device further includes a modulator coupled to said resonator circuit and operable to modulate the output of the resonator circuit where either the ferromagnetic mass or the coil is disposed in an animal such as a human. some embodiments allow for disposing multiple devices in an animal for characterizing different animal motions.

Abstract: A method of estimating the blood flow rate of a heart ventricle assist device which is positioned externally of, or implanted in, a patient. The assist device comprises a blood pump having a rapidly rotating, electrically powered impeller, and comprises briefly interrupting power to the impeller to cause its rotation to slow. From this, blood viscosity can be estimated, which viscosity is used to obtain real time, estimated blood flow rates and pressure heads. Apparatus for accomplishing this is disclosed.

Abstract: Embodiments of the disclosed technology are directed to a self-contained, totally implantable blood pump that replaces the whole heart. It is a small spherical device that encloses all of its blood propulsion dynamics. The dynamics are controlled by a built-in microcontroller that regulates the speed of the motor in response to hemodynamic changes like blood pressure fluctuations, level of body activity, and/or posture. The hemodynamic changes are detected using a plurality of sensors disposed around the body. An implantable transcutaneously rechargeable battery provides power to the microcontroller, motor and/or sensors.

Abstract: Upon failure of a primary control unit for controlling an implanted pump in a ventricle assist system enhancing blood flow in a patient, an initial backup control unit is substituted for the failed unit. An interface device is connected to one of the initial backup control unit or the primary control unit. Patient-unique data is downloaded to the interface device to create a transfer data set. The initial backup control unit is connected to the implanted pump as a new primary control unit. The interface device is connected to a replacement backup control unit. The transfer data set is uploaded from the interface device to the replacement backup control unit. The transfer data set on the interface device is modified after uploading to prevent a subsequent uploading from the interface device to another control unit.

Abstract: At least one aspect is directed to a totally artificial heart, and at least another aspect is directed to a method of controlling blood flow in a patient. The totally artificial heart may include a first rotary pump having an input to receive blood and an output to provide blood to a patient's lungs, a second rotary pump having an input to receive blood and an output to provide blood to the patient's body, a first sensor associated with the first rotary pump, a second sensor associated with the second rotary pump, and a control system coupled to the first sensor, the second sensor, the first rotary pump and the second rotary pump and configured to control characteristics of the first rotary pump and the second rotary pump based on signals received from at least one of the first sensor and the second sensor such that an average flow of blood through the second rotary pump is greater than an average flow of blood through the first rotary pump.

Abstract: A TET system is operable to vary an amount of power transmitted from an external power supply to an implantable power unit in accordance with a monitored condition of the implantable power unit. The amount of power supplied to the implantable power unit for operating a pump, for example, can be varied in accordance with a cardiac cycle, so as to maintain the monitored condition in the power circuit within a desired range throughout the cardiac cycle.

Abstract: Methods and apparatus for controlling the operation of, and providing power for and to, implantable ventricular assist devices which includes a pump employing a brushless DC motor-driven blood pump, are disclosed. In one embodiment, a control system for driving an implantable blood pump is provided. The digital processor is responsive to data associated with the operation of the pump received at the data transfer pump, and from program data stored in the memory, (i) to determine therefrom, the identity of the pump, (ii) to determine therefrom, electrical characteristics and features of the identified pump, and (iii) to adaptively generate and apply to the data port, control signals for driving the identified pump.

Abstract: A method of estimating the blood flow rate of a heart ventricle assist device which is positioned externally of, or implanted in, a patient. The assist device comprises a blood pump having a rapidly rotating, electrically powered impeller, and comprises briefly interrupting power to the impeller to cause its rotation to slow. From this, blood viscosity can be estimated, which viscosity is used to obtain real time, estimated blood flow rates and pressure heads. Apparatus for accomplishing this is disclosed.

Abstract: An extracorporeal blood processing method using a blood circuit comprising a pair of blood passages attached to opposite flow ends of a blood treatment device and said blood circuit is mounted on a blood pump console, the method includes: withdrawing blood from a vascular system of a human patient and drawing the blood into the blood circuit; pumping the withdrawn blood through one of the pair of blood passages using a first blood pump of the console and into the blood treatment device; pumping the treated blood from the treatment device through the other of the pair of blood passages using a second blood pump of the console; infusing the treated blood from the other blood passage and into the vascular system of the patient, and periodically reversing a flow direction of blood through the pair of blood passages and blood treatment device.

Abstract: The present invention is thus directed to methods and apparatus for decreasing pressure in a first portion of a vessel of the cardiac structure of a patient by implanting a shunt communicating with an area outside said first portion, whereby a volume of blood sufficient to reduce pressure in said first portion is released. Preferably, the first portion comprises the left ventricle and the pressure reduced is the end diastolic pressure, which is accomplished by having the shunt communicate with the left ventricle so a small volume of blood is released from the left ventricle to reduce the end diastolic pressure.

Abstract: A physiologic control method and system for an implantable blood pump includes operating the pump at a predetermined speed and monitoring the patient's diastolic pump flow rate. The predetermined speed is varied in response to the diastolic pump flow rate. The pump speed may further be adjusted in response to the patient's heart rate. The speed may be increased and decreased in response to corresponding changes in the diastolic pump flow rate, and increased in response to an increase in heart rate.

Abstract: A physiologic control system and method for controlling a blood pump system such as a VAD system. The pump system includes, for example, a blood pump and a controller for controlling the pump. The system may further include a flow measurement device. A desired peak to peak flow amplitude is determined, and then adjusted in response to various system parameters either manually or automatically by the system.

Abstract: The flow rate of blood in an implantable blood pump is determined at least in part based on a parameter related to thrust on the rotor of the pump. The parameter may be a parameter related to displacement of the rotor along its axis, such as a function of the back electromotive force generated in one or more coils of the stator. The back electromotive force may be measured during open-phase periods of a particular coil or set of coils, during which no power is applied to the coil or set of coils by the motor drive circuit. The parameter related to thrust may be used in conjunction with the speed of rotation of the rotor, the magnitude of current supplied to the rotor, or both to determine the flow rate. The pump may be controlled responsive to the determined flow rate.

Abstract: The present invention is directed to methods and apparatus for decreasing pressure in the left atrium of a patient by implanting a valved shunt through the atrial septum, whereby a volume of blood sufficient to reduce pressure in said left atrium is released to the right atrium.

Abstract: A system and method for controlling extracorporeal blood flow in a patient. The system includes a blood pump having a rotor, a plurality of rollers carried by the rotor and a pump chamber extended in tension about the rollers. A sensor measures an operating parameter of the blood pump and a controller, coupled to the sensor, calculates the flow efficiency of the blood pump based on the measured operating parameter. The controller is further configured to display the flow efficiency on the display device, and the operation of the blood pump is adjusted based on the flow efficiency when necessary.

Abstract: An artificial heart pump system is provided independently with a controlling processor for controlling an operation status of a blood pump so as to perform in a preset condition and with an observing processor for controlling a display unit displaying an operation status and an operation condition of the blood pump. In addition, a memory device is mounted in an outside-the-body type battery pack included in the artificial heart pump system; data such as pump data, event log or the like is stored therein; and data are collected and managed automatically by a battery charger when charging the battery charger for a daily performance. Further, an interface unit of an artificial heart pump is proposed where a user can confirm displayed contents of the controller without exposing the controller externally.

Abstract: Methods and apparatus for decreasing cardiac pressure in a patient by implanting a shunt communicating with an area outside a first portion, whereby a volume of blood sufficient to reduce pressure in a first portion is released. Preferably, the end diastolic pressure in the left ventricle is reduced, which is accomplished by having the shunt communicate with the left ventricle so a small volume of blood is released from the left ventricle. Most preferably, the shunt selectively permits flow when a pressure differential between the left ventricle and another chamber of a heart above a threshold pressure, so that shunting is prevented during left ventricular systole, or, alternatively, selectively permits flow when a pressure differential between the left ventricle and another chamber of a heart is between a lower threshold and a higher threshold. In certain embodiments a semi-passive check-valve is controlled and actuated by an external signal.

Abstract: A demand responsive physiological control system for use with a rotary blood pump; said system including a pump controller which is capable of controlling pump speed of said pump; said system further including a physiological controller, and wherein said physiological controller is adapted to analyse input data relating to physiological condition of a user of said pump; and wherein said physiological controller determines appropriate pumping speed and sends a speed control signal to said pump controller to adjust pump speed; said system further including a physiological state detector which provides said input data indicative of at least one physiological state of said user, in use, to said physiological controller.

Abstract: A device and a method for working with electromagnetic fields, specifically those fields that occur in image-guided nuclear spin tomography examinations (MRT or MRI). More precisely, the invention concerns an at least partially implanted medical device (IMD) that permits the delivery of electrical stimulation impulses by an electrode only in timeframes, in which no electromagnetic interferences are recognized and/or the control unit performs a reconstruction of electrical measurements for the timeframes in which electromagnetic interferences are recognized.

Abstract: A method of controlling the speed of a blood pump, wherein the method includes the steps of deriving an estimated pulsatility index from speed, then deriving an estimated blood pressure from estimated pulsatility index; and maintaining target blood flow rate near to or at a preset value by adjusting the speed.

Abstract: A method of estimating the blood flow rate of a heart ventricle assist device which is positioned externally of, or implanted in, a patient. The assist device comprises a blood pump having a rapidly rotating, electrically powered impeller, and comprises briefly interrupting power to the impeller to cause its rotation to slow. From this, blood viscosity can be estimated, which viscosity is used to obtain real time, estimated blood flow rates and pressure heads. Apparatus for accomplishing this is disclosed.

Abstract: A blood pump system for an artificial heart including: a control unit for controlling a blood pump, the control unit including a first alarm generating part for generating a first alarm signal according to the state of the blood pump, and a speaker for outputting an audible sound upon receiving the first alarm signal when the blood pump is in an abnormal state; a supervisory section configured to supervise the state of the control unit; a determining section configured to determine whether the control unit is in an abnormal state or not, based on output signal from the supervisory section; and a second alarm generating part for generating a second alarm signal according to the state of the control unit, based on the result of determination by the determining section.

Abstract: Materials and methods related to blood pump systems are described. These can be used in patients to, for example, monitor arterial pressure, measure blood flow, maintain left ventricular pressure within a particular range, avoid left ventricular collapse, prevent fusion of the aortic valve in a subject having a blood pump, and provide a means to wean a patient from a blood pump.

Abstract: A blood pump including a ultrasonic sensor mounted in or on a blood contacting surface of said blood pump. The ultrasonic sensor measures blood velocity and reports information to a blood pump controller and wherein the ultrasonic sensor is directed to measure blood velocity in an inflow cannula connected to the blood pump.

Abstract: In a left ventricular assist device (LVAD) a rotodynamic blood pump (10) is powered by a brushless DC motor (12). A power supply (14) supplies power to the motor (12). Three feedback channels, one for each of voltage, current, and motor speed lead to a microcontroller or microprocessor (18). The three feedback waveforms are analyzed, and from these waveforms, motor input power, patient heart rate, current pump flow rate, and systemic pressure are determined. The microprocessor (18) then calculates a desired flow rate proportional to the patient heart rate. The microprocessor communicates a new power output to a commutation circuit (16), which regulates power to the motor (12). The pump (10) also includes safety checks that are prioritized over desired pump flow. These include prevention of ventricular suction, low pulsatility, minimum and maximum pump speed, minimum speed-relative pump flow, minimum absolute pump flow, minimum and maximum motor input power.

Abstract: A method of estimating the blood flow rate of a heart ventricle assist device which is positioned externally of, or implanted in, a patient. The assist device comprises a blood pump having a rapidly rotating, electrically powered impeller, and comprises briefly interrupting power to the impeller to cause its rotation to slow. From this, blood viscosity can be estimated, which viscosity is used to obtain real time, estimated blood flow rates and pressure heads.

Abstract: An artificial heart pump system has a heart pump is-implanted in a patient. A pump control unit worn by a patient includes a programmable device for adapting a secure aspect of heart pump operation in response to pump operating commands. The pump control unit has a wired interface and a wireless interface. A clinical external unit is adapted to be connected to the wired interface for delivering a pump operating command to the pump control unit. An auxiliary external unit is adapted to be connected to the wireless interface for collecting patient and/or pump system performance-related data from the pump control unit. The wireless interface is unable to consummate a pump operating command.

Abstract: A blood pump system for an artificial heart including: a control unit for controlling a blood pump, the control unit including a first alarm generating part for generating a first alarm signal according to the state of the blood pump, and a speaker for outputting an audible sound upon receiving the first alarm signal when the blood pump is in an abnormal state; a supervisory section configured to supervise the state of the control unit; a determining section configured to determine whether the control unit is in an abnormal state or not, based on output signal from the supervisory section; and a second alarm generating part for generating a second alarm signal according to the state of the control unit, based on the result of determination by the determining section.

Abstract: Since disruptive forces can be continuously exerted upon a rotor during a pulsatile flow through a pump with a magnetically mounted rotor (permanent magnets and addition control current coils), it is necessary to adjust position i.e. modify axial rotor position very quickly. The control current should only result in small amounts of losses. According to the invention, the current is pulse-width modulated by the control current coils by means of a set value predetermined by a controller which is arranged downstream from a position sensing system. If the set value is high, it is switched to a higher voltage level and the real value of the position sensing system is stored for a defined period of time, respectively beginning with the switching flank of the control current, and the position sensing system is disconnected during said period of time.

Abstract: An apparatus for a heart assist device, comprising a processing unit for computing the blood flow rate from the arterial pressure curve and for predicting at every heartbeat the closing time of the heart valve from the curve of the blood flow rate. The processing unit is adapted to deliver a signal for controlling a heart assist device at a point in time, a period ahead in time of the closing time of the heart valve, wherein the mechanical properties of the said heart assist device are taken into account in determining the period. The apparatus adapts itself to changes in a patient's heart frequency and aortic pressure.

Abstract: A blood pump may be adapted to sense the onset of left ventricular collapse by monitoring a pulsatility index, and may adjust the pump speed to maintain the index at a setpoint. The pulsatility index may be measured by the amount of difference between the maximum and the minimum volume of flow through the pump during a particular time period. The setpoint may be increased when the onset of ventricular collapse is detected, for example, when the pulsatility index falls suddenly. The setpoint may be decreased incrementally when the onset of ventricular collapse has not been detected for a period of time, such as for a particular period of time since the last detection of the onset of ventricular collapse.

Abstract: An apparatus for a heart assist device, comprising a processing unit for computing the blood flow rate from the arterial pressure curve and for predicting at every heartbeat the closing time of the heart valve from the curve of the blood flow rate. The processing unit is adapted to deliver a signal for controlling a heart assist device at a point in time, a period ahead in time of the closing time of the heart valve, wherein the mechanical properties of said heart assist device are taken into account in determining said period. The apparatus adapts itself to changes in a patient's heart frequency and aortic pressure.

Abstract: A balloon is positionable in the patient's descending aorta. The balloon includes a balloon catheter and two pressure sensors that electrically couple to an extra-corporeal controller. The balloon itself also couples pneumatically to the extra-corporeal controller. An extra-corporeal pump electrically couples to the extra-corporeal controller, the pump having an outlet connectable to the patient's infra-diaphragmatic The pump inlet is connectable via a cannula to the patient's supra-diaphragmatic artery. artery. A doctor inserts the balloon into the descending aorta, and positions the balloon near the level of the patient's diaphragm. A balloon catheter, coupled to the extra-corporeal controller, inflates and deflates the balloon. An electrocardiogram ECG and proximal aortic blood pressure, measured in the upper arterial compartment via a lumen in the balloon catheter, serve as inputs to cycle the balloon synchronously with the heartbeat.

Abstract: A blood pump is joined in parallel flow between the left ventricle and aorta of a patient's heart. The pump includes an inlet pressure sensor and cooperating controller for measuring inlet pressure to the pump to control operation thereof. The controller adjusts speed of the pump in a closed loop control using feedback of the measured inlet pressure to conform operation of the pump with the natural cycle of the heart.

Abstract: A biventricular cardiac prosthesis has a flow balance control system to balance blood flow through the left and right sides of the prosthesis to maintain a patient's left atrial pressure within physiologic bounds. The prosthesis can be configured to have flow characteristics so that a signal representative of the difference in hydraulic pumping pressures on the left and right sides of the prosthesis is representative of the difference between left and right atrial pressures of a patient having the prosthesis implanted. This signal can be used as a control signal to drive the prosthesis so that left atrial pressure is approximately equal to right atrial pressure, and within physiologic bounds. A specific prosthesis includes left and right pumping sections, each having a blood pumping chamber and a hydraulic fluid chamber, with a reciprocating hydraulic pump driving systole alternately on the right and left sides.

Abstract: A system for assisting the failing ventricle, which utilizes a single blood displacement chamber and a single cannula. The cannula is inserted into the failing ventricle cavity and is connected to a blood displacement actuator. The device produces blood displacement at a critical time for a critical duration and with blood flow time course such that it improves the systolic function of the heart: augments the cardiac output and increases the generated pressure. The device also improves the diastolic function by increasing the ventricle compliance and imposing rapid relaxation of the ventricle wall. The device provides additional external work without deteriorating the mechanical function of the failing ventricular, moreover it decreases the energy consumption of the failing heart and improves the coronary perfusion. Consequently, the device improves the balance between the energy supply (coronary perfusion) to the ventricle wall and the mechanical demands, and allows recovery of the failing heart.

Abstract: An apparatus and method for relieving stress on a heart muscle tissue in a wall of a heart having a chamber. A plurality of biocompatible and implantable elongate strips are configured to be connected to the heart wall and disposed about the chamber such that the elongate strips are arranged in spaced relation to one another. The elongate strips are bendable and are sufficiently resistant to elongation such that natural stretching of the heart wall does not cause elongation of the plurality of strips.

Abstract: An electrohydraulic energy converter useful in a circulatory assist device includes a housing defining a hydraulic fluid flow path and having first and second open ends. A left diaphragm is disposed on and seals the first open end of the housing, and a right diaphragm is disposed on and seals the second open end of the housing. A reversible axial flow pump is disposed within the housing for reversibly pumping hydraulic fluid along the hydraulic fluid flow path. In another embodiment, a blood pump is provided for alternately driving left and right systole in a circulatory assist device. The blood pump includes an energy converter having left and right blood pumping elements disposed on and sealing the two open ends of the housing. In a further embodiment, the axial flow pump includes a stator, a rotor rotatably connected to the stator, several impeller blades disposed around and extending radially outward from the rotor, and a motor for imparting mechanical movement on the rotor.

Abstract: An apparatus for use in an artificial heart assembly includes an internal coil adapted to be implanted beneath the skin of a subject and an external coil coupled to transmit electric power to the internal coil through the skin of the subject. The apparatus includes a DC-to-AC converter coupled to the external coil which selectively converts DC power from a DC power source into either a first frequency or a second frequency, the first frequency having a plurality of cycles each of a first duration and the second frequency having a plurality of cycles each of a second duration longer than the first duration. The DC-to-AC converter comprises four switching components each coupled in parallel with a respective one of four passive components and a drive circuit operatively coupled to the switching components.

Abstract: A ventricular assist device 10 includes a blood conduit 14, which carries the blood ejected from the ventricle to the ventricular assist device, a one-way valve 22, which is provided in the blood conduit and can open only toward the ventricular assist device, an afterload-controlling chamber 11, which temporarily stores the blood ejected from the ventricle, a pressure sensor 23, which measures the pressure in the afterload-controlling chamber, a blood pump 25 and a control unit 26 thereof, a blood conduit 16 that carries the blood to an artery, and a probe 27 for measuring blood flow rate and a flowmeter 28, which control the flow rate of the blood pump 25. The pressure of the afterload-controlling chamber 11 is controlled so as to keep the one-way valve closed during ventricular diastole, and also controlled so as to direct all the blood ejected from the ventricle into the afterload-controlling chamber 11 during ventricular systole.

Abstract: A centrifugal impeller-type pump for transporting blood has a new and improved design in the impeller, to allow for the elimination of stagnant flow areas, and a geometrical design that minimizes damage to the blood components. A system for controlling and stabilizing the speed of centrifugal-type pumps used in a human cardiovascular system is also provided. Further provided are methods of corrosion protection and enhancing thromboresistance, rejection of waste heat, and methods to connect the artificial heart to the cardiovascular system as a Left Ventricle Assist Device (LVAD) and as a Total Artificial Heart (TAH).

Abstract: An artificial heart assembly may be provided with a blood inlet conduit adapted to be implanted within a subject, a blood outlet conduit adapted to be implanted within the subject, a pumping mechanism implanted within the subject that pumps blood from the blood inlet conduit to the blood outlet conduit, and a motor coupled to drive the pumping mechanism. The artificial heart apparatus has a power source and a control circuit operatively coupled to cause the motor to drive the pumping mechanism in a regular mode when the power source has a relatively high charge level and in an irregular mode when the power source has a relatively low charge level so that the subject can feel when the pumping mechanism is being driven in the irregular mode and thus know that the power source has the relatively low charge level.