Abstract: A cardiac pacing system comprising one or more leadless cardiac pacemakers configured for implantation in electrical contact with a cardiac chamber and configured to perform cardiac pacing functions in combination with a co-implanted implantable cardioverter-defibrillator (ICD). The leadless cardiac pacemaker comprises at least two leadless electrodes configured for delivering cardiac pacing pulses, sensing evoked and/or natural cardiac electrical signals, and bidirectionally communicating with the co-implanted ICD.

Abstract: A detection method for detecting a QRS wave is disclosed. An electrocardiogram (ECG) signal is provided. The ECG signal is enhanced to generate a processed signal. A first crest of the processed signal is determined. Each crest following the first crest is defined as a second crest. The level of each second crest is higher than a first threshold value. The result of defining the second crest is utilized to determine whether the QRS wave has occurred and approached a first crest.

Abstract: An acoustic energy delivery system for delivering acoustic energy to an implantable medical device (“IMD”). The system includes an IMD having a power source and an energy delivery device. The energy delivery device includes a controller and an array of ultrasonic elements electrically coupled to the controller and configured to deliver acoustic energy to the IMD. Methods of delivering acoustic energy to an IMD are also disclosed.

Abstract: An external coil assembly for a transcutaneous system is disclosed. The assembly comprises: a housing having a skin-adjacent surface, an opposing exposed surface and a threaded shaft open to the exposed surface and extending toward the skin-adjacent surface; an external coil secured within the housing; and a magnet with a threaded exterior surface to threadingly engage the threaded shaft, wherein at least one of either the shaft thread or the magnet thread has at least one transverse channel forming discontinuities in the thread.

Abstract: A system, method and implantable medical for concurrently providing a therapeutic output to a patient while communicating transcutaneously with an external device. The therapeutic output is provided to the patient with an implantable medical device wherein an electromagnetic signal is associated with at least one of recharging of a rechargeable power source and providing the therapeutic output. Bi-directional transcutaneous communication is conducted via via telemetry between the implantable medical device and an external device using a telemetry signal while the telemetry signal and the electromagnetic signal occur simultaneously.

Abstract: An implantable system and method for deep brain stimulation (DBS) treatments. The implantable system is sufficiently small and self-contained to enable implantation of the entire system within the brain, or optionally within the brain and the surrounding tissue. The system comprises an implantable inductor on which a voltage is induced when subjected to an electromagnetic field, and an implantable device comprising a housing, stimulating elements at an exterior surface of the housing, and electronics within the housing and electrically connected to the implantable inductor. The electronics produces a brain-stimulating current from the voltage induced on the implantable inductor and then delivers the brain-stimulating current to the stimulating elements. Deep brain stimulation is performed by subjecting the inductor to an electromagnetic field to induce a voltage on the inductor that powers the electronics to produce and deliver the brain-stimulating current to the stimulating elements.

Abstract: An improved external charger for an implantable medical device is disclosed in which charging is at least partially controlled based on a sensed pressure impingent on its case, which pressure is indicative of the pressure between the external charger and a patient's tissue. The improved external charger includes pressure detection circuitry coupled to one or more pressure sensors for controlling the external device in accordance with the sensed impingent pressure. The sensed pressure can be used to control charging, for example, by suspending charging, by adjusting a maximum set point temperature for the external charger based on the measured pressure, or by issuing an alert via a suitable user interface. By so controlling the external charger on the basis of the measured pressure, the external charger is less likely to create potentially problematic or uncomfortable conditions for the user.

Abstract: Apparatus and methods for charging a power cell in an implantable medical device (“IMD”) are disclosed herein. In one embodiment, a method includes providing an electrical pulse to an inductor external to the IMD. A frequency of an oscillation signal induced in the inductor by the current pulse is measured. The inductor is driven with an oscillating signal having a frequency based on the measured frequency of the oscillation signal. The power cell is charged using current induced in the IMD by the driving of the inductor.

Abstract: The present invention is related to active implantable medical devices comprising an antenna and a band diplexer connected to said antenna. The band diplexer comprises first filter means for a first signal to be transmitted and/or received in a first RF band and second filter means for a second signal to be transmitted and/or received in a second RF band. A method of bidirectional wireless communication is disclosed between an active implantable medical device and an external device, comprising the steps of: communicating unidirectionally from the external device to the implantable medical device over a first wireless link in a first RF band in the MI near-field and communicating unidirectionally from the implantable medical device to the external device over a second wireless link in a second RF band in the EM field.

Abstract: A controller-transmitter transmits acoustic energy through the body to an implanted acoustic receiver-stimulator. The receiver-stimulator converts the acoustic energy into electrical energy and delivers the electrical energy to tissue using an electrode assembly. The receiver-stimulator limits the output voltage delivered to the tissue to a predetermined maximum output voltage. In the presence of interfering acoustic energy sources output voltages are thereby limited prior to being delivered to the tissue. Furthermore, the controller-transmitter estimates the output voltage that is delivered to the tissue by the implanted receiver-stimulator. The controller-transmitter measures a query spike voltage resulting from the electrical energy delivered to the tissue by the receiver-stimulator, and computes a ratio of the predetermined maximum output voltage and a maximum query spike voltage. The maximum query spike voltage is computed by detecting a query spike voltage plateau.

Abstract: An external defibrillator having a battery; a capacitor electrically communicable with the battery; at least two electrodes electrically communicable with the capacitor and with the skin of a patient; a controller configured to charge the capacitor from the battery and to discharge the capacitor through the electrodes; and a support supporting the battery, capacitor, electrodes and controller in a deployment configuration, the defibrillator having a maximum weight per unit area in the deployment configuration of 0.1 lb/in2 and/or a maximum thickness of 1 inch. The support may be a waterproof housing.

Abstract: A pulse generating implantable medical device comprises a power source , a control unit, a plurality of switching units, a timing unit, a pulse generating unit adapted to generate one or more stimulation pulses to be applied to human or animal tissue via one or more stimulation electrodes, and a coupling capacitor in series with each stimulation electrode. A stimulation pulse is adapted to be applied during a stimulation pulse timing cycle that includes a stimulation phase and a recharge phase, and that the timing of a stimulation pulse timing cycle is controlled by the control unit via the timing unit and the switching units. The implantable medical device further comprises an energy storage unit and that, during the recharge phase, one or more of the switching units is adapted to establish electrical connection between the one or many stimulation electrodes and the energy storage unit in order to collect and store energy from applied stimulation pulses.

Abstract: User interface for external power source, recharger, for an implantable medical device. At least some of patient controls and display icons of an energy transfer unit are common with at least some of the patient controls and the display icons of a patient control unit. An energy transfer unit is operable by the patient with less than three operative controls to control energy transfer from the external energy transfer unit to the implantable medical device. An external antenna having a primary coil can inductively transfer energy to a secondary coil of the implantable medical device when the external antenna is externally placed in proximity of the secondary coil. An energy transfer unit has an external telemetry coil allowing the energy transfer unit to communicate with the implantable medical device through the internal telemetry coil in order to at least partially control the therapeutic output of the implantable medical device.

Abstract: Systems including an implantable receiver-stimulator and an implantable controller-transmitter are used for leadless electrical stimulation of body tissues. Cardiac pacing and arrhythmia control is accomplished with one or more implantable receiver-stimulators and an external or implantable controller-transmitter. Systems are implanted by testing external or implantable devices at different tissue sites, observing physiologic and device responses, and selecting sites with preferred performance for implanting the systems. In these systems, a controller-transmitter is activated at a remote tissue location to transmit/deliver acoustic energy through the body to a receiver-stimulator at a target tissue location. The receiver-stimulator converts the acoustic energy to electrical energy for electrical stimulation of the body tissue. The tissue locations(s) can be optimized by moving either or both of the controller-transmitter and the receiver-stimulator to determine the best patient and device responses.

Abstract: By incorporating magnetic field-inducing position determination coils (PDCs) in an external charger, it is possible to determine the position of an implantable device by actively inducing magnetic fields using the PDCs and sensing the reflected magnetic field from the implant. In one embodiment, the PDCs are driven by an AC power source with a frequency equal to the charging coil. In another embodiment, the PDCs are driven by an AC power source at a frequency different from that of the charging coil. By comparing the relative reflected magnetic field strengths at each of the PDCs, the position of the implant relative to the external charger can be determined. Audio and/or visual feedback can then be communicated to the patient to allow the patient to improve the alignment of the charger.

Abstract: A magnetic core flux canceling device according to embodiments of the present invention includes a magnetic field sensor adapted for placement at a ferrite material core in an implantable medical device, the magnetic field sensor adapted to transmit a signal corresponding to a magnitude of a first magnetic field. Such a device may also include a coil disposed around the ferrite material core and a driver circuit configured to receive the signal and to vary a voltage applied across the coil based on the signal, the voltage applied across the coil creating a second magnetic field at least partially in a direction opposite the first magnetic field. According to some embodiments of the present invention, multiple coils may be used to cancel magnetic fields in multiple directions. A voltage applied across the coil varies in magnitude and/or direction to cancel or weaken an MRI-related magnetic field.

Abstract: Some embodiments of a cardiac stimulation system may include a plurality of electrode assemblies that are interconnected by one or more wires while at least one of the electrode assemblies (e.g., a control electrode) wirelessly receives energy through inductive coupling with a power communication unit external to the heart (e.g., a device implanted along one or more ribs). These embodiments may provide an arrangement for efficient inductive coupling from the power communication unit to the control electrode. Also, in some circumstances, the cardiac stimulation system may eliminate the need for wired leads that extend to a location outside the heart, thereby reducing the likelihood of infection that passes along the wire and into the heart.

Abstract: A cochlear implant system has an implantable portion that includes a stimulator module for producing for the auditory system of a user an electrical stimulation signal representative of an acoustic signal. The implantable portion further includes a battery for supplying power to the stimulator module, a receiver module for receiving an electrical power signal across the skin of a user, and a recharge module that uses the electrical power signal to recharge the battery. The recharge module recharges the battery at less than the maximum recharge rate.

Abstract: An external processor device is described for an implantable prosthetic system. An external processor housing has a generally planar skin contacting surface and a central axis perpendicular to the skin contacting surface. A signal processor is located within the processor housing for developing an implant data signal. The processor housing also contains a transmitter coil for coupling the implant data signal across the skin to the implantable prosthetic system. A battery compartment is also located within the processor housing in an annular region around the central axis for containing a battery arrangement to provide electrical power to the signal processor and the transmitter coil.

Abstract: A charging system is disclosed. In one embodiment, the system includes a charging unit having a primary coil, and an implantable medical device comprising a secondary coil to receive charge from the primary coil. The implantable medical device further includes a half-wave voltage-doubling rectifier coupled to the secondary coil, a full-wave rectifier coupled to the secondary coil, and a rechargeable power source. Control logic is provided to periodically configure the rechargeable power source to receive charge from a selected one of the voltage-doubling circuit and the full-wave rectifier in a manner that increases rate at which charge is transferred from the secondary coil to the rechargeable power source. The control logic may configure the rechargeable power source to receive charge based on one or more monitored conditions which may include, for example, an indication of a current, a voltage, a coupling coefficient, back-scatter, and temperature.

Abstract: A charging system for an implantable medical device having a secondary coil. The charging system includes an external power source having at least one primary coil, a modulation, circuit operatively coupled to the primary coil and capable of driving it in a manner characterized by a charging parameter, and a sensor in communication with the modulation circuit and capable of sensing a condition indicating a need to adjust the charging parameter during a charging process. The parameter may be varied so that data sensed by the sensor meets a threshold requirement, which may be based on a patient preference, a government regulation, a recommendation promulgated by a health authority and/or a requirement associated with another device carried by the patient. In one embodiment, the regulation dictates maximum magnetic field exposure, and a field limiting circuit is employed to adjust the charging process.

Abstract: An AED includes defibrillation circuitry housed within an enclosure, a first processor programmed to periodically test the operability of the defibrillation circuitry and a second processor in communication with the first processor. The AED further includes a visual indicator, such as a red/green LED, positioned at the exterior of the enclosure that is operatively connected to the second processor. The second processor is programmed to control the visual indicator in response to the periodic test results provided to it by the first processor.

Abstract: Techniques for determining whether a medical device will be able to deliver stimulation according to a particular program throughout a useable voltage range of a power source of the medical device are described. According to some examples, the medical device configures a DC to DC converter of the medical device in a specified output configuration and delivers electrical stimulation from the medical device according to a program while at the specified output configuration. Whether the medical device will be able to deliver stimulation according to the program when the power source is at a power source voltage level lower than a present voltage level used during therapy delivery is determined based on a value of a voltage drop across a regulator module determined while delivering the electrical stimulation according to the program. The determination for a program may be performed, as an example, when the program is created or modified.

Abstract: Techniques are disclosed for recharging an Implantable Medical Device (IMD). In one embodiment, a first external coil is positioned on one side of a patient's body, such as on a front side of the torso in proximity to the IMD. A second external coil is positioned on an opposite side of the patient's body, such as on the back of the torso. A recharging device generates a current in each of the coils, inductively coupling the first and the second coils to the secondary recharge coil of the IMD. According to another aspect, each of the two external coils may wrap around a portion of the patient's body, such as the torso or head, and are positioned such that the IMD lies between the coils. According to this aspect, current generated in the coils inductively couples to a second recharge coil that is angled within the patient's body.

Abstract: An apparatus and method can receive wireless energy using a wireless electrostimulation electrode assembly. In certain examples, at least some of the received wireless energy can be delivered as an electrostimulation to a heart. In certain examples, the wireless electrostimulation electrode can be mechanically supported at least partially using a ring formed by an annulus of a mitral valve of the heart. In certain examples, the wireless electrostimulation electrode assembly can be configured to be intravascularly delivered to an implant location within a chamber of the heart at the annulus of the mitral valve of the heart, and can fit entirely within the heart.

Abstract: In a cochlear implant system, the implantable stimulator includes a monitor which monitors parameters associated with the stimulation signals and/or the power stored in an energy storage element which stores energy transmitted from the processor. This parameter or parameters is/are analyzed and one or more feedback signals are generated and transmitted back to the processor. The processor uses the feedback signal to insure that power is transmitted to the stimulator optimally and that the stimulation signals are compliant.

Abstract: Electrotherapeutic implant for stimulation of body tissue, comprising at least two electrode poles (14) which are connected to electric feeder lines, a demodulation unit (22), at least one electric feeder line (20), which is designed as an antenna and contacts the demodulation unit (22), wherein the implant (10) is fabricated from one piece, can be affixed (16) at the treatment site and is equipped with a biocompatible insulation, whereby the components of the implant (10) are designed so that a therapeutic energy which can be injected from the outside over the antenna (20) during the treatment is delivered to the therapeutic target region without intermediate storage.

Abstract: A rechargeable implantable medical device with a magnetic shield placed on the distal side of a secondary recharging coil to improve charging efficiency is disclosed. The rechargeable implantable medical device can be a wide variety of medical devices such as neuro stimulators, drug delivery pumps, pacemakers, defibrillators, diagnostic recorders, cochlear implants. The implantable medical device has a secondary recharging coil carried over a magnetic shield and coupled to electronics and a rechargeable power source carried inside the housing. The electronics are configured to perform a medical therapy. Additionally a method for enhancing electromagnetic coupling during recharging of an implantable medical device is disclosed, and a method for reducing temperature rise during recharging of an implantable medical device is disclosed.

Abstract: A mechanism for transferring energy from an external power source to an implantable medical device is disclosed. An antenna is positioned in proximity of the implantable medical device. The position of a core of the antenna is adjusted relative to the implantable medical device while the antenna is maintained substantially stationary. A frequency of transmission of a power source is adjusted, and the antenna is driven at the adjusted frequency to transfer energy transcutaneously to the implantable medical device. In one embodiment, the frequency of transmission is selected based on an amplitude of a signal in the antenna.

Abstract: A wireless system for monitoring a patient's brain tissue including (1) a plurality of electrodes abutting brain tissue, (2) main circuitry outside the patient's body to transmit power at radio frequencies and send/receive data using infrared energy, and (3) subcutaneously-implanted remote circuitry connected to the electrodes and configured to (a) receive transmitted RF power, (b) capture and digitize EEG signals from the electrodes, and (c) send/receive data to/from the main circuitry using IR energy, including sending digitized EEG signals from each electrode to capture the full bandwidth of each EEG signal. The system preferably includes circuitry to measure the electrical impedance of each electrode for real-time monitoring of the condition of the electrode/tissue interfaces to enhance interpretation of captured EEG signals.

Abstract: A transcutaneous energy transfer system, transcutaneous charging system, external power source, external charger and methods of transcutaneous energy transfer and charging for an implantable medical device and an external power source/charger. The implantable medical device has a secondary coil adapted to be inductively energized by an external primary coil at a carrier frequency. The external power source/charger has a primary coil and circuitry capable of inductively energizing the secondary coil by driving the primary coil at a carrier frequency adjusted to the resonant frequency to match a resonant frequency of the tuned inductive charging circuit, to minimize the impedance of the tuned inductive charging circuit or to increase the efficiency of energy transfer.

Abstract: An implantable stimulation system includes a stimulation current generator encased in an implantable housing, one or more stimulation leads to deliver therapeutic stimulation from the generator to target patient tissue, and inductive elements arranged to condition the stimulation for delivery to the target tissue with increased efficiency and reduced pain sensation. The inductive elements are arranged external to the housing and integral with one or more of a stimulation lead or an external component of the housing, such as a header. The inductive elements serve to condition therapeutic stimulations such that varying the output of the generator allows the system to deliver arbitrary effective waveforms to the target tissue.

Abstract: A bio-implantable energy capture and storage assembly, including an acoustic energy transmitter for contact with the skin, and an acoustic energy receiver—converter for converting acoustic energy to electrical energy; and a battery or capacitor connected to the energy converter. The acoustic energy receiver/converter is contained within a biocompatible implant.

Abstract: The present invention provides, among other things, a sensor system, having (1) a sensor implanted in a body part of the subject, wherein the sensor has a first antenna, and (2) a sensor reader worn on the subject's body part, wherein the sensor reader has a band housing a second antenna, which is inductively coupled with the first antenna, for enabling the sensor reader to communicate with the sensor.

Abstract: Apparatus, system, and method that include a pacing apparatus having a stent electrode through which pulses of electrical current can be delivered. Stent electrodes receive energy for generating the electrical current from a variety of sources. Sources include from one or more induction coils that can form at least a portion of the stent. Sources can also include an implantable pulse generator coupled to a lead through which pulses of the electrical current are supplied to the stent electrodes.

Abstract: Endocardial or intravascular cardiac pacemaker having a sealed housing, in which a battery and a pacemaker controller connected to the battery, as well as at least one stimulation pulse generator, are situated, the housing being oblong and having a length of less than 70 mm and a cross-sectional area of less than 100 mm2 and carrying at least two electrodes, each of which has an outwardly directed, electrically conductive surface and is implemented as a stimulation electrode and is at least sometimes electrically connected to the stimulation pulse generator via an electrical connection situated in the interior of the housing.

Abstract: A system is disclosed for stimulating body tissue includes one or more leadless, battery-less, implantable electrodes; and an external controller configured to transmit energy to the implantable electrode(s) via an RF signal for generating tissue stimulating pulses emitted by the respective electrode(s). The external controller is preferably further configured to transmit identification information to the implantable electrode(s) for secured information exchange. The one or more implantable electrodes are preferably each configured to transmit sensed tissue information to the external controller via an RF signal. The system may employ fixation technologies such as screw-in mechanisms, stent-like scaffolding, cuff-type or anchoring mechanisms in order to attach the implanted electrode(s) to respective target body tissues, such as (without limitation) cardiac tissue, brain tissue, bladder tissue, diaphragm, nerve tissue, spine, digestive tract tissue, and muscle tissue.

Abstract: A mechanism for transferring energy from an external power source to an implantable medical device is disclosed. An antenna is positioned in proximity of the implantable medical device. The position of a core of the antenna is adjusted relative to the implantable medical device while the antenna is maintained substantially stationary. A frequency of transmission of a power source is adjusted, and the antenna is driven at the adjusted frequency to transfer energy transcutaneously to the implantable medical device. In one embodiment, the frequency of transmission is selected based on an amplitude of a signal in the antenna.

Abstract: Systems including an implantable receiver-stimulator and an implantable controller-transmitter are used for leadless electrical stimulation of body tissues. Cardiac pacing and arrhythmia control is accomplished with one or more implantable receiver-stimulators and an external or implantable controller-transmitter. Systems are implanted by testing external or implantable devices at different tissue sites, observing physiologic and device responses, and selecting sites with preferred performance for implanting the systems. In these systems, a controller-transmitter is activated at a remote tissue location to transmit/deliver acoustic energy through the body to a receiver-stimulator at a target tissue location. The receiver-stimulator converts the acoustic energy to electrical energy for electrical stimulation of the body tissue. The tissue locations(s) can be optimized by moving either or both of the controller-transmitter and the receiver-stimulator to determine the best patient and device responses.

Abstract: A transmission circuit for an RF inductive link, particularly for an implanted device such as a cochlear implant. In a preferred form, the transmission circuit 1 includes a transmitter coil 24 and a damping device, including an auxiliary coil 4 and switch 6. The switch is operated to close the coil circuit when data zeros are transmitted. This has the advantage of improving modulation depth without placing stress on the RF driver output switches.

Abstract: System, method and antenna for an external power source for an implantable medical device having therapeutic componentry and a secondary coil operatively coupled to the therapeutic componentry. A housing has a first surface adapted to be placed closest to the secondary coil of the implantable medical device. A primary coil is operatively coupled to the external power and is capable of inductively energizing the secondary coil, the primary coil being wound forming generally concentric loops having an axis. The housing has a protrusion extending from the first surface.

Abstract: Circuitry useable to protect and reliably charge a rechargeable battery, even from a zero-volt state, is disclosed, and is particularly useful when employed in an implantable medical device. The circuit includes two charging paths, a first path for trickle charging the battery at a relatively low current when the battery voltage is below a threshold, and a second path for charging the battery at relatively higher currents that the battery voltage is above a certain threshold. A passive diode is used in the first trickle-charging path which allows trickle charging even when the battery voltage is too low for reliable gating, while a gateable switch (preferably a PMOS transistor) is used in the second higher-current charging path when the voltage is higher and the switch can therefore be gated more reliably. A second diode between the two paths ensures no leakage to the substrate through the gateable switch during trickle charging.

Abstract: The present invention refers to a device used to recharge the battery of electronic cardiac implants, like implanted pacemakers and defibrillators. It can be used to recharge the battery after an emergency requirement, such as: defibrillation or in diagnosis and or reprogramming of implants, during which no energy is demanded from the internal battery, seeing that the energy feed becomes guaranteed (accepted) by the proposed device. The invention is composed by three essential components: a generator (A), a transmitter unit (B) and a receptor coil (C). The generator is destined to produce an energy signal with determined amplitude and frequency and that is carried across through a coaxial cable to the transmitter unit (B). The emitted magnetic field is captured by the receptor coil (C) that is implanted inside the human body, generating a voltage with the absence of the Gibbs phenomenon.

Abstract: An implantable stimulation system comprises an implantable stimulator and a control device. The control device is configured to transmit acoustic waves to the implantable stimulator, and the implantable stimulator is configured to transform the acoustic waves into electrical current, and generate stimulation energy based on the electrical current. For example, the electrical current can be transformed into electrical energy that can be used to generate the stimulation energy. Or the electrical current can contain signals used to directly or indirectly control the generation of the stimulation energy.

Abstract: A device for optimizing transmitting energy and transmitting position for an implantable electrical stimulator is provided. The device utilizes a design of a wireless energy transmitting and positioning device with an external energy-feedback control, which can automatically detect an optimum energy-transmitting position through an external antenna performing an adjustable energy transmission method, and through a wireless-feedback control method to provide the optimum energy. As such, the implantable electrical stimulator can exactly and effectively stimulate the nervous muscle.

Abstract: Receiver-stimulators comprise a nearly isotropic transducer assembly, demodulator circuitry, and at least two tissue contacting electrodes. Use of near isotropic transducers allows the devices to be implanted with less concern regarding the orientation relative to an acoustic energy source. Transducers or transducer elements having relatively small sizes, typically less than ½ the wavelength of the acoustic source, enhance isotropy. The use of single crystal piezoelectric materials enhance sensitivity.

Abstract: System for transcutaneous energy transfer to an implantable medical device adapted to be implanted under a cutaneous boundary having a housing having a first surface adapted to face the cutaneous boundary, the first surface of the housing of the implantable medical device having a first mating element, therapeutic componentry and a secondary coil operatively coupled to the therapeutic componentry. An external power source has housing having a first surface adapted to be placed closest to the cutaneous boundary, the first surface of the housing of the external power source having a second mating element and a primary coil capable of inductively energizing the secondary coil when externally placed in proximity of the secondary coil. The first mating element and the second mating element are configured to tactilely align the external power source with the implantable medical device.

Abstract: Receiver-stimulators comprise a nearly isotropic transducer assembly, demodulator circuitry, and at least two tissue contacting electrodes. Use of near isotropic transducers allows the devices to be implanted with less concern regarding the orientation relative to an acoustic energy source. Transducers or transducer elements having relatively small sizes, typically less than ½ the wavelength of the acoustic source, enhance isotropy. The use of single crystal piezoelectric materials enhance sensitivity.

Abstract: An apparatus includes a medical device for implantation in a blood vessel and a power supply adapted to be located outside the blood vessel. The extravascular power supply has a power transmitter that produces a radio frequency signal which is applied to an energy transmitting antenna. The energy transmitting antenna comprises first and second coils connected is series and wound around separate spaced apart, parallel axes axis wherein magnetic fields generated by each coil add together to produce a cumulative field. The receiving antenna, for positioning in a near field region of the cumulative field, has least one coil wound around a third axis that is aligned with the cumulative field.

Abstract: The implantable, electrically operated medical device system comprises an implanted radio frequency (RF) receiving unit (receiver) incorporating a back-up rechargeable power supply and an implanted, electrically operated device, and an external RF transmitting unit (transmitter). RF energy is transmitted by the transmitter and is coupled into the receiver which is used to power the implanted medical device and/or recharge the back-up power supply. The back-up power supply within the receiver has enough capacity to be able to, by itself, power the implanted device coupled to the receiver for at least 24 hours during continual delivery of medical therapy. The receiver is surgically implanted within the patient and the transmitter is worn externally by the patient. The transmitter can be powered by either a rechargeable or non-rechargeable battery. In a first mode of operation, the transmitter will supply power, via RF coupled energy, to operate the receiver and simultaneously recharge the back-up power supply.