Abstract: A rate-responsive dual-chamber pacemaker and pacing method for supporting the heart with electrical stimulation at a pacing rate driven by the heart's sinus node or, alternatively, by a sensor adapted to determine the patient's metabolic demand (a metabolic demand indicator). The pacemaker automatically selects between the indicated rates to determine the best pacing rate for appropriately satisfying metabolic demand at all times. The natural rate, driven by the sinus node, takes precedence over the metabolic indicator rate provided the natural rate meets a standard determined by the metabolic demand indicator rate. The pacemaker upper rate response mechanism allows atrioventricular synchrony at natural sinus rates ranging from low rates to high exercise rates, even up to the programmed maximum rate, but maintains ventricular rate stability during pathological atrial tachycardias by reverting to pacing in a rate-responsive VVI mode.

Abstract: A method and apparatus for applying an asymmetric biphasic exponential waveform countershock to the heart useful in an implantable cardioverter or defibrillator, wherein the second phase has a start amplitude of substantially one half that of the first phase, and wherein the polarity of a capacitor discharging through a current path including the heart is reversed. A voltage reversing circuit may include a voltage shifter which shifts voltage associated with switching elements in the circuit to reduce voltage stresses in the switching elements.

Abstract: A cardioverting/defibrillating pacemaker with the ability to sense and respond to haemodynamic compromise. The ventricular pressure (VP) and electrical activity of the heart are sensed via one or more transvenous or epicardial devices. The filtered peak-to-peak amplitude (VFPPA) or a peak pressure function (VPPF) based upon the right and/or left VP waveform(s) are derived. In one embodiment the VP and the electrical activity of the heart are sensed and processed continuously, and the VFPPA or the VPPF continuously derived. The VFPPA or the VPPF, and the ECG are used to initiate bradycardia pacing, antitachycardia pacing and cardioversion/defibrillation therapies. In another embodiment the VP and electrical activity of the heart are continuously sensed. The electrical activity is processed continuously and used to determine whether or not some irregularity exists. If so, one of the VPPF or VFPPA is derived and used to decide which of the therapies are to be used.

Abstract: An apparatus for administering electrotherapy, such as a pacemaker, having an alarm system including a relatively small alarm electrode affixed to the external surface of a non-conductive portion of the case of the apparatus, such as the neck. The apparatus, is implanted with the alarm electrode in contact with a muscle. A switch permits the alarm electrode to be used as the indifferent electrode for providing a patient alarm. The amplitude of the output may be varied to provide different alarm levels; i.e. different twitching intensity of the muscle, to permit the patient and physician to distinguish between alarms of diagnostic interest and those indicating a hazardous or emergency condition.

Abstract: An apparatus and method for tachyarrhythmia reversion provides a pacing pulse to the atrium at a predetermined time prior to the delivery of a cardioversion shock to the ventricle. The pacing pulse depolarizes the atrium producing an atrial refractory period., The cardioversion shock therapy is delivered during this refractory period in order to avoid the vulnerable zone of the atrium. This minimizes post-shock arrhythmias attributable to shock delivery during the atrial vulnerable zone. When used with bradycardia support pacing, a post-shock therapy pacing delay or pause is introduced, following reversion of the tachyarrhythmia, before delivering the bradycardia support pacing. The magnitude of the delay period is substantially greater than the normal bradycardia support pacing standby interval.

Abstract: An improved ultrasonic transducer for a catheter tip has a thin strip of piezoelectric polymer film formed into a spiral ring and adhesively mounted on the support structure near the catheter tip. Electrical connection between the back face of the film and the support structure negative electrode is via capacitive coupling. Connection to the front face of the film is via a wire connected to the positive electrode of the catheter. A further embodiment suitable for a needle transducer is formed by coating the tip with a solution of PVDF co-polymer to form the actual transducer.

Abstract: A terminal for detachably connecting an electrical lead to an electrical device is disclosed. The terminal includes a stationary support structure adapted to be fixed to the device, and a movable structure adapted to be carried by the stationary support structure for movement between first and second positions relative to the support structure. The movable structure has a plurality of wall members thereon that are movable relatively toward and away from one another between a first spaced apart position less than the diameter of the electrical lead and a second spaced apart position greater than the diameter of the electrical lead for receiving and releasing the lead in the second spaced apart position and for gripping the lead in the first spaced apart position.

Abstract: An arrhythmia control system and method having automatic determination of the tachycardia confirmation interval. The interval is dynamically set at the minimum of an absolute detection interval and a value calculated as a function of either average sinus interval or tachycardia cycle length or both. The continued presence or the reversion of a pathologic tachycardia can be reliably confirmed, particularly when the patient experiences an elevated heart rate due to, for example, exercise, prior to onset of the tachycardia.

Abstract: Apparatus and method of antitachycardia pacing in a duel chamber pacing device including means for or steps of detecting the presence of a tachycardia, measuring the tachycardia cycle length, determining a VA interval value less than or equal to the tachycardia cycle length, determining an initial value of the AV delay interval, delivering pulses to the ventricle and to the atrium until the expiration of N VA intervals and N AV intervals thereby completing a first train of pulses, delivering a series of M trains of pulses similar to said first train pulses, and varying the AV delay interval value from the initial value at least once prior to the completion of the series of M trains of pulses. Monitoring of instrinsic QRS complexes between pulse trains is performed. If the tachyarrhythmia is deemed to be accelerating, one of cardioversion or defibrillation may be applied.

Abstract: The cardiac pacing system includes a cardiac pacer and a multiconductor pacing lead having a distal end and a proximal end. The pacer comprises a metal case with insulated conductor feedthroughs in a top side thereof and a neck mounted to the top side of the metal case. The neck is made of a soft pliable material and spring contacts are provided in the neck for connecting the cardiac pacer with the pacing lead.

Abstract: The cardiac lead comprises a tubular body having a proximal end and a distal end, a coiled conductor within the tubular body defining a lumen therein and having a distal end and a proximal end, a tip electrode mounted at the distal end of the tubular body, and an elongate stiffener wire comprising an elongate member made of a wire having a preset shape, a distal end and a proximal end positioned within the tubular body. The stiffener wire includes an electrical insulative material covering the elongate member for the length thereof to prevent short circuiting of the coils of the coiled conductor which may come in contact with the elongate member. A sleeve is provided for connecting a portion of the distal end of the coiled conductor to the tip electrode and for fixing the distal end of the elongate member at the distal end of the tubular body.

Abstract: A cardiac sense amplifier network includes a differential amplifier, a bandpass filter, a comparator network, a microprocessor, an analog-to-digital converter, and a random-access memory. The differential amplifier is responsive to incoming electrical signals containing cardiac signals and noise signals for amplifying the electrical signals and for producing amplified electrical signals. The filter is used to filter the amplified electrical signals and for producing filtered electrical signals. The comparator network compares the filtered electrical signals with first and second reference voltages and produces a flag signal indicative of when the filtered electrical signals exceed the first or second reference voltages. The microprocessor is responsive to the flag signal for initializing the same and for generating a control signal.

Abstract: An improved ultrasonic transducer for a catheter tip has a thin strip of piezoelectric polymer film formed into a spiral ring and adhesively mounted on the support structure near the catheter tip. Electrical connection between the back face of the film and the support structure negative electrode is via capacitive coupling. Connection to the front face of the film is via a wire connected to the positive electrode of the catheter. A further embodiment suitable for a needle transducer is formed by coating the tip with a solution of PVDF co-polymer to form the actual transducer.