Abstract: An implantable electrode for stimulating tissue has a piezoelectric electrode for electrically and mechanically stimulating tissue and for detecting electrical and mechanical evoked response of the stimulated tissue. An implantable lead and an implantable stimulation device employing such an electrode are described including diagnostic circuitry for making a diagnosis of the heart condition using such an electrode.

Abstract: In an apparatus for terminating atrial fibrillation using pulses having an energy content which is the same as the energy content of conventional pacing pulses, stimulation pulses are respectively emitted by a number of electrodes disposed at different sites in or on a heart experiencing atrial fibrillation. When atrial fibrillation is detected, waveforms are measured at each of the electrodes, and the electrode having the waveform exhibiting the shortest interval between successive identifiable, cyclical waveform characteristics, such as successive P-waves, is selected as a first electrode for beginning an atrial defibrillation attempt. Stimulation pulses are emitted from the first electrode at a stimulation rate which is slightly shorter than the aforementioned shortest interval and the other electrodes are stimulated at a rate which is slightly shorter than the rate for the first electrode. All of the stimulation pulses are delivered starting at the latest local detection point in time.

Abstract: In a method and apparatus for physiological signal processing, a number of measured physiological signals are obtained in vivo from a subject and at least one of these measured physiological signals is supplied to the input of each first signal processing unit in a group of first signal processing units. Within each signal processing unit, the physiological measurement signal (or signals) supplied thereto is/are subjected to at least one transfer function so as to produce a pre-treated signal at the output of that first signal processing unit. The pre-treated signals from all of the first signal processing units are combined in a second signal processing unit so as to produce at least one synthesized ECG signal.

Abstract: An implantable heart defibrillator includes a pulse generator controlled by a control unit for emitting defibrillation pulses. The pulse generator is controllable to emit a number of low-energy defibrillation pulses, having a lower pulse amplitude and a shorter pulse duration than a conventional defibrillation pulse, with the total energy in the number of low-energy defibrillation pulses being less than the energy in a conventional defibrillation pulse. Each pulse in the number of low-energy defibrillation pulses, however, contains enough energy to depolarize heart cells oriented favorably in relation to the direction of the electrical field of the low-energy defibrillation pulse.

Abstract: A reset circuit for resetting a memory system following a radiation event includes an error detect circuit for producing an error signal in response to detection of an uncorrectable error in the systems memory arrays, and includes a control circuit for selectively resetting at least select portions of the memory system in response to the error detect signal. All or portions of the memory arrays can be reset by the control circuit, and complete or selective latch reset, or selective power recycling are provided. In one embodiment, the control circuit provides latch reset in response to the error detect signal so as to reset the memory latches without recycling power, and in another embodiment, the control circuit selectively cycles power to independent memory zones of the system to reset only those zones whose memory array is identified as having an uncorrectable error.

Abstract: An apparatus for determining a physical condition in a living subject by determining peripheral resistance to flow is wherein peripheral resistance to flow is determined by measuring changes in the pressure drop characteristic in an artery during diastole. The pressure drop characteristic can be determined by measuring absolute pressure, relative pressure or dimensional changes in the artery during diastole. The apparatus can advantageously be used in a rate-responsive heart stimulator.

Abstract: An apparatus for producing heart defibrillation sequences formed of stimulation pulses and defibrillation shocks contains a unit for delivering pulses through an intracardiac or epicardiac electrode, normally for cardiac pacing, and defibrillator circuitry for delivering defibrillation shocks through defibrillation electrodes. The unit for delivering pacing pulses has an output stage which is capable of generating a stimulation pulse, delivered to the heart via the pacing electrode, having a higher energy content than a pacing pulse, but considerably less energy than a conventional defibrillation shock. A control unit is connected to the unit for delivering stimulation pulses and to the defibrillator circuitry for forming a defibrillation sequence consisting of stimulation pulses and defibrillation shocks. The control unit determines the timing for delivering the stimulation pulses and the defibrillation shocks.

Abstract: A heart defibrillator includes a defibrillation circuit for delivering defibrillation pulses. The defibrillation circuit also emits a pre-pulse before the defibrillation pulse. The pre-pulse is not as intense as the defibrillation pulse, but is still intense enough to induce mechanical contraction of muscles in parts of the thorax and possibly the heart.

Abstract: An implantable heart defibrillator is equipped with at least one intracardiac defibrillation electrode. A post-therapy apparatus is arranged to emit, after a defibrillation pulse, at least one stimulation pulse through the defibrillation electrode, the stimulation pulse having energy far higher than the energy in a normal heart stimulation pulse for cardiac pacing, but less energy than a normal defibrillation pulse.

Abstract: A rate-responsive heart stimulator with a variable stimulation interval contains a measurement device which generates a measurement signal corresponding to the volume of blood in a heart during the blood-filling phase (diastole) and a comparator which compares the measurement signal with a defined threshold value corresponding to a defined degree of blood filling. The comparator generates a control signal when the measurement signal reaches the threshold value, the control signal representing the time elapsing since the last stimulation pulse, and controlling the heart stimulator's stimulation interval.

Abstract: In a method for increasing the energy output from a number of charged capacitors each of the capacitors is discharged, one after another, through a load. The capacitors are then coupled in series in successive, different combination, each of which includes a part or all of the capacitors. These combinations are and being discharged, one after another, through the load. An apparatus for increasing the energy output from a number of charged capacitors includes comprises a charging circuit, arranged to control the charging of the capacitors, and a controllable switching device, arranged to first connect each of the capacitors to a load for discharge of the capacitors, on after another. The switching device then couples the capacitors in series in successive, different combinations, each of which includes a part or all of the capacitors, and connects the respective combinations to the load for discharge of the series couplings, on after another.

Abstract: In order to be able to set a current distribution in the heart in the event of defibrillation which is optimum both spatially and temporally, a pulse-generating device is provided having n-1 outputs connected in series, to which a total of n output terminals and n electrodes are connected. The device generates output pulses at its outputs which temporally overlap one another at different times and in different numbers.

Abstract: A cardiac pacer which generates pacing pulses at a predetermined pacing rate, includes a device for generating an alternating signal which is unable to pace the heart. The pacing pulses and the alternating signal are transmitted together to the heart. The alternating signal after transmittal to the heart is measured and processed such that a respiratory signal is obtained. The predetermined pacing rate is then varied dependent on the respiratory signal.

Abstract: A heart pacemaker has a pulse generator and circuitry for measuring a respiration signal of the user and a control unit for controlling the pulse generator by changing the pulse repetition rate dependent on the respiration signal. A heart action detector is provided for acquiring heart action signals and the respiration signal measuring circuitry includes detectors for measuring the amplitude fluctuations in the heart action signal and supplying those fluctuations to the control unit.

Abstract: An atrium-controlled heart pacemaker has a monitoring circuit for interrupting tachycardia which may be generated by the pacemaker. The monitoring circuit includes a P-wave counter and a window generator connected thereto. The window generator prescribes a window for the P-wave counter within which a predetermined maximum number n of P-waves is allowed to appear. When the n.sup.th P-wave appears in the window, forwarding of the n+1.sup.th P-wave to the stimulation circuit is blocked.

Abstract: An atrium controlled heart pacemaker has a switching stage which is controlled in dependence upon the appearance of atrial signals. The switching stage switches the heart pacemaker to a VVI mode for a predetermined number of stimulation pulses or natural ventricular events, or a predetermined time, upon the appearance of at least one atrial signal before a selected time limit. The time limit is derived from the difference between a smallest synchronous interval and the AV delay.

Abstract: An atrium-controlled heart pacemaker operates using set parameters including a smallest synchronous interval (SSI) between two stimulation pulses, a minimum atrial-ventricular delay time (AVmin) and a maximum atrial-ventricular delay time (AVmax). A control unit, dependent upon the appearance of an atrial signal, controls operation of the pacemaker such that the pacemaker operates with a variable pulse rate (DDD mode) when the atrial signal appears after a point in time SSI-AVmin, operates the pacemaker with a highest synchronous pulse rate when the atrial signal is between the points in time SSI-AVmin and SSI-AVmax, and causes no stimulation pulses to be emitted when the atrial signal appears before the point in time SSI-AVmax.