Abstract: A multi-chamber cardiac pacing systems for providing synchronous pacing to at least the two upper heart chambers or the two lower heart chambers or to three heart chambers or to all four heart chambers employing one or more field density clamp (FDC) sense amplifiers for accurately sensing and timing cardiac depolarizations of the right and left heart chambers is disclosed. The synchronous pacing of one of the right and left heart chambers is provided on demand following expiration of programmable pace CDW and sense CDW that are started by both a paced event and a sensed event first occurring in the other of the right and left heart chambers. The delivery of the pacing pulse is inhibited by a sensed event detected in the other of the right and left heart chambers before the expiration of the corresponding CDW.

Abstract: An implantable cardioverter for providing cardioversion electrical energy to at least one chamber of a patient's heart in need of cardioversion and applying a pain alleviating therapy at an appropriate site in the patient's body prior to or in conjunction with the delivery of the cardioversion energy to the heart chamber to alleviate propagated pain perceived by the patient. The combined cardioversion and pain alleviating therapies are preferably realized in a single implantable, multiprogrammable medical device or separate implantable cardioversion and pain control devices with means for communicating operating and status commands between the devices through the patient's body.

Abstract: Methods and apparatus for interrogation of implantable medical device (IMD) information, including programmed parameter values, operating modes and programmed changes thereof and data stored in the IMD, by emission of audible sounds by the IMD are disclosed. The IMD includes an audio transducer that emits audible sounds including voiced statements or musical tones stored in analog memory correlated to a programming or interrogation operating algorithm or to a warning trigger event. The audible sounds can comprise the sole uplink transmission or may augment the contemporaneous uplink RF transmission of stored data, and/or programmed operating modes and parameters and/or device operations and states in an interrogation or during programming. To conserve energy, the audible sounds accompanying interrogation and programming of the IMD are at a low volume that preferably cannot be heard without use of an external audio amplifier or stethoscope.

Abstract: Pacemaker designed for support of both orthotopic and heterotopic transplants has three lead bore connector block assembly and dedicated or dedictable amplifiers for pacing and sensing configurations unique to transplant situations. The provision of definable amplifier assignments allows for enhanced sensing, capture detection and therapy.

Abstract: An adaptive, performance-optimizing communication system for communicating with an implanted medical device in which signals are transmitted and received in accordance with predetermined, interrelated operational parameters, such as transmission rate, transmitter power, and the like. Various aspects of system performance, including bit error rate in received signals, the strength of received signals, the signal-to-noise ratio of received signals, the presence of local RF noise and non-telemetry related RF signals, and the like, are dynamically monitored by the communication system, to determine whether predetermined system performance goals are being met. If it is determined that one or more system performance goals are not being met, one or more operational parameters may be automatically adjusted so that desired performance can be achieved.

Abstract: A feedthrough configuration for a hermetically sealed implantable medical device which includes a metal case having an aperture and a feedthrough in the aperture which includes an electrically conductive pin, an insulating material supporting the pin, a block spaced from the case and in electrical continuity with the pin and a device for electrical protection connected to the block and to the case. The device for electrical protection preferably includes two zener diodes, a first diode connected at the block and a second diode connected to the case with an electrical conductor connecting the two diodes in a back-to-back configuration.

Abstract: An implantable cardioverter for providing cardioversion electrical energy to at least one chamber of a patient's heart in need of cardioversion and applying a pain alleviating therapy at an appropriate site in the patient's body prior to or in conjunction with the delivery of the cardioversion energy to the heart chamber to alleviate propagated pain perceived by the patient. The combined cardioversion and pain alleviating therapies are preferably realized in a single implantable, multiprogrammable medical device or separate implantable cardioversion and pain control devices with means for communicating operating and status commands between the devices through the patient's body.

Abstract: A system and corresponding method for steering stimulus pulses to one or more selected cardiac sites are disclosed. An apparatus and corresponding method permit improved capture and easy adjustment of the stimulus pulse when the threshold level changes, without simply increasing stimulus power or replacing the implanted lead. Substantially concurrent pulses may be delivered across one, two or more anode electrodes and a corresponding common or cathode electrode, where the pulse amplitude, pulse duration or pulse phase characteristics of each individual component pulse are adjusted to permit the resulting composite pulse to be steered or directed towards a desired target cardiac site.

Abstract: A cardiac pacemaker with an analog telemetry system. A calibration circuit within the pacemaker is adapted to provide a reference signal of known character to the pacemaker's telemetry system. The reference signal is transmitted across the telemetry link as if it were an actual cardiac signal, and received by an external programmer. Since the reference signal has known, predetermined qualities, the programmer can automatically calibrate and scale the telemetry signal from the pacemaker, thereby increasing the accuracy of the telemetry channel. The increased accuracy is particular useful in assessing rejection of a transplanted heart, which is known to be associated with a 15% decline in the peak R-wave amplitude of the cardiac signal.

Abstract: A system and method for communicating with a medical device implanted in an ambulatory patient and for locating the patient in order to selectively monitor device function, alter device operating parameters and modes and provide emergency assistance to and communications with a patient. The implanted device includes a telemetry transceiver for communicating data and operating instructions between the implanted device and an external patient communications control device that is either worn by or located in proximity to the patient within the implanted device transceiving range. The control device preferably includes a communication link with a remote medical support network, a global positioning satellite receiver for receiving positioning data identifying the global position of the control device, and a patient activated link for permitting patient initiated personal communication with the medical support network.

Abstract: A feedthrough configuration for a hermetically sealed implantable medical device which includes a metal case having an aperture and a feedthrough in the aperture which includes an electrically conductive pin, an insulating material supporting the pin, a block spaced from the case and in electrical continuity with the pin and a device for electrical protection connected to the block and to the case. The device for electrical protection preferably includes two zener diodes, a first diode connected at the block and a second diode connected to the case with an electrical conductor connecting the two diodes in a back-to-back configuration.

Abstract: An adaptive, performance-optimizing communication system for communicating with an implanted medical device in which signals are transmitted and received in accordance with predetermined, interrelated operational parameters, such as transmission rate, transmitter power, and the like. Various aspects of system performance, including bit error rate in received signals, the strength of received signals, the signal-to-noise ratio of received signals, the presence of local RF noise and non-telemetry related RF signals, and the like, are dynamically monitored by the communication system, to determine whether predetermined system performance goals are being met. If it is determined that one or more system performance goals are not being met, one or more operational parameters may be automatically adjusted so that desired performance can be achieved.

Abstract: An implantable cardioverter for providing cardioversion electrical energy to at least one chamber of a patient's heart in need of cardioversion and applying a pain alleviating therapy at an appropriate site in the patient's body prior to or in conjunction with the delivery of the cardioversion energy to the heart chamber to alleviate propagated pain perceived by the patient. The combined cardioversion and pain alleviating therapies are preferably realized in a single implantable, multi-programmable medical device or separate implantable cardioversion and pain control devices with means for communicating operating and status commands between the devices through the patient's body.

Abstract: An enclosure for use in pacemaker as well as other implantable medical devices has a substantially planar lid which is welded to a circumferential flange formed on a deep drawn shield. The shield and lid form a "container" which is encased in a compliant shroud which isolates the welded flange from direct body contact and which enhances the biocompatibility of the entire device. A resilient and compliant shroud material accepts connector module components, integrates seals, provides storage for lead wrap, and provides a simple low cost and reliable method of attaching stimulating leads or other structures required by the medical device.

Abstract: A pump having a housing with an integral fluid reservoir and flexible end plates to permit the pump to be run dry for an extended period of time. A pair of reservoirs are provided, one each side of a pumping chamber. These reservoirs are in fluid communication with the pumping chamber via openings provided through the end plates of the pumping chamber and slots in the impeller hub. When the pump is run dry, fluid stored in these reservoirs is permitted to be released into the pumping chamber to provide a lubrication between the impeller and the chamber walls, thus reducing friction. The chamber end plates are thin and flexible. These end plates can bow outwardly due to the impeller expanding from increased heat when the pump is run dry, and thus reduce friction with the impeller. Accordingly, the pump can be run dry for an extended period of time without damaging or destroying the pump impeller.

Abstract: Electrical tissue stimulator and method for limiting the programmability of stimulation pulse parameters. The tissue stimulator includes a plurality of electrodes and a memory for holding a stimulation pulse parameter limit value and a programmed parameter value of a stimulation pulse. A pulse generator applies electrical stimulation pulses to the electrodes in accordance with the programmed parameter value. Programming means is included for receiving remotely generated programming signals and altering the contents of the memory in accordance with the signals. Means is included for comparing the stimulation pulse parameter limit value and the programmed parameter value and for preventing an alteration of the programmed parameter value, unless it is within stimulation pulse parameter limits. The stimulation pulse parameters may include pulse amplitude, pulse width, and pulse rate and the programmed parameter limit values may be upper and lower limits.

Abstract: An implantable medical device uses a solid-state sensor for detecting the application of an external magnetic field. The sensor includes first and second split-drain field-effect transistors (MAGFETs) which are cross-coupled such that an external magnetic field perpendicular to the channel regions of the MAGFETs causes an increase in current through one split-drain half of each MAGFET, and a decrease in current through the other split-drain half of each MAGFET. The sensor also includes a high-gain differential amplifier coupled between the MAGFETs for detecting changes in the current conducted through the respective split-drain halves, and produces an output voltage which changes upon application of an external magnetic field to the implantable medical device. The magnetic sensor operates at low power supply voltages and bias currents available in implantable medical devices such as a cardiac pacemaker, so that current drain and power consumption are minimized.

Abstract: An improved method for manufacturing a sophisticated cam profile liner used in pumps and compressors. A non-circular cam profile liner is fabricated from multiple parts, preferably two identical cam liner halves mated together. Each cam profile liner half is generally crescent-shaped, and is manufactured from a single mold using conventional molding techniques. Window openings are formed in the cam profile liner without the need for hand-placing inserts in the mold. Further, no taper is formed in the cam profile liner. Accordingly, the present invention is suitable for use in precision sliding vane pumps, as well as flexible and roller-type pumps. Since each cam profile liner half is identical to the other, a symmetrical cam chamber is defined by the cam profile liner.

Abstract: A cardiac pacemaker with an analog telemetry system. A calibration circuit within the pacemaker is adapted to provide a reference signal of known character to the pacemaker's telemetry system. The reference signal is transmitted across the telemetry link as if it were an actual cardiac signal, and received by an external programmer. Since the reference signal has known, predetermined qualities, the programmer can automatically calibrate and scale the telemetry signal from the pacemaker, thereby increasing the accuracy of the telemetry channel. The increased accuracy is particular useful in assessing rejection of a transplanted heart, which is known to be associated with a 15% decline in the peak R-wave amplitude of the cardiac signal.

Abstract: A method and apparatus for estimating the remaining capacity of a lithium-iodine battery through the nomographic analysis of two or more measurements of battery impedance. In a preferred embodiment, a pacemaker or other implantable medical device is provided with circuitry for periodically measuring the internal impedance of its battery. Each measurement of impedance is stored along with an indication of when such measurement was made. Nomographic analysis, based upon the rated capacity of the battery and the expected internal impedance at various stages of depletion, allows for two or more time-stamped impedance measurements to serve as the basis for an extrapolation to estimate the remaining service life of the implantable medical device. Nomographic analysis may be performed by circuitry contained in the implanted device itself; in the alternative, periodic impedance measurements may be communicated to external processing circuitry via a telemetry channel.