Abstract: In a cardiac stimulating device and method for biventricular stimulation, the V-V interval between the stimulation pulses to the right and left ventricles is variable, and a farfield ECG obtained from measuring electrodes located outside of the heart is used for monitoring the mechanical synchronization between the right and left ventricles. The mechanical synchronization is optimized by an automatic adjustment of the V-V interval until the ORS duration is minimized.

Abstract: An implantable cardiac stimulation device operates according to a first pacing algorithm executable by a microprocessor and which is able to independently perform stimulation therapy for a patient's heart, as well as according to a second pacing algorithm which is also microprocessor-executable. The first and second algorithms actively generate stimulation parameters during each cardiac cycle, but the stimulation parameters generated by the second algorithm are only permitted to result in actual stimulation therapy if those parameters fall within parameter ranges that are calculated to be allowable for stimulation by the first algorithm.

Abstract: A cardiac lead has an end adapted for contact with cardiac tissue that has a number of dot-like electrodes which are separated from each other by electrically insulating material, and which are positioned at respective locations adapted for simultaneous contact with the cardiac tissue. The dot-like electrodes produce respective unipolar signals. At least one difference signal from the unipolar signals of a pair of the dot-like electrodes. The difference signal is edited in circuitry of a cardiac assist device and is compared to a threshold. If the threshold is exceeded, a signal indicating a cardiac rhythm abnormality, such as fibrillation, is generated for triggering electrical therapy delivered to the cardiac tissue by the cardiac assist device.

Abstract: A circuit and method for detecting cardiac rhythm abnormalities employ unipolar signals respectively obtained from a cardiac lead having a tip at which a number of separate electrodes are disposed, the electrodes being simultaneously in contact with cardiac tissue. The respective unipolar signals which are obtained from the multiple electrodes exhibit a time relationship relative to each other, and this time relationship is analyzed to determine whether a cardiac rhythm abnormality is present or one or more of the unipolar signals is compared to a template which is known to represent a cardiac abnormality. Analysis of the time relation is undertaken by determining the absolute value of a time offset between any two of the unipolar signals, or by correlating any two of the unipolar signals.

Abstract: In an implantable electrode for an electrode lead for a stimulation device for stimulating tissue, the electrode is formed as a biocompatible piezoelectric electrode which is adapted to be in direct electrical contact with tissue for electrically and mechanically stimulating the tissue and for detecting electrical and mechanical evoked response of the stimulated tissue. The stimulation device can include circuitry for making a diagnosis of a heart condition using signals received from the implantable electrode.

Abstract: An implantable medical device has a pressure sensing arrangement to measure right ventricular pressure of a heart including a pressure sensor adapted to be positioned in the right ventricle of the heart, to measure the pressure and to generate a pressure signal in response to the measured pressure. The pressure sensing arrangement also has a pressure signal processor and a timing unit. The processor determines from the pressure signal, using diastolic timing signals from the timing unit based on the pressure signal identifying the diastolic phase, a diastolic pressure signal representing the ventricular pressure only during the diastolic phase of the heart cycle.

Abstract: A pacemaker has control circuits contained in an enclosure and a lead containing an electrical conductor connected to an electrode for delivering electrical stimulation pulses to a heart. The stretching of a wall in the ventricle, corresponding to adequate filling of the ventricle in the heart, is determined in order to identify a time of emitting the stimulation pulses. This stretching is measured indirectly by measurement of pressure in the ventricle using a pressure sensor disposed near the lead in the ventricle. The signal from the sensor is supplied via the lead to circuitry in the enclosure, wherein the signal is amplified and is supplied to an edge detector, which detects an increasing or positive edge of the signal.

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: 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.