Abstract: An improved pacer for controlling tachycardia. Placing a magnet over the patient's chest results in the generation of two pulses, the time separation between which is an indication of the battery potential. Application of the magnet in this way also holds the device off, after the two pulses are generated, so that if the device is causing him discomfort the patient can temporarily disable it until the physician can program it off. Application of a magnet to the patient's chest, or programming of the device, also resets two start-of-scan time intervals to the values programmed by the physician. The next scanning begins with the programmed time values. In this way the physician, after inducing tachycardia, can verify the programmed time parameters rapidly by observing the patient's ECG waveform, without having to wait several minutes until scanning from previously retained successful values would otherwise progress to the programmed values.

Abstract: There is disclosed an improved pacer for controlling tachycardia. Following each tachycardia confirmation, a burst of stimulating pulses is generated. The rates of the bursts increase from cycle to cycle; thus following each tachycardia confirmation, a pulse burst at a different rate is generated. The number of pulses in a burst is similarly scanned, a complete rate scan taking place for each pulse number in a scan. The rate of a burst and the number of pulses in it which are successful in terminating tachycardia are stored, and following the next tachycardia confirmation the stored rate and pulse number are used for the first burst which is generated. In this manner, there is a greater likelihood that tachycardia will be terminated following the first burst since a previously successful rate and pulse number are used. Only if success is not achieved does scanning of the burst rate and pulse number ensue, starting with the previously successful rate and pulse number.

Abstract: There is disclosed a three-board electronic assembly construction for a heart pacer which solves the numerous problems presented by prior art two-board assemblies without increasing the pacer size. The size of the unit is also held to a minimum by providing a simple flat sheet of resilient material for constraining all of the sub-assemblies within the pacer case, and by judiciously placing two RF filter capacitors in the region of the terminal assembly the capacitors do not add to the bulk of the overall unit.

Abstract: There is disclosed a direct-coupled output stage which is especially advantageous for use in an implantable heart pacer. In order to provide for charge balancing at the electrode/electrolyte interfaces, the electrodes are shorted to each other after a pacing pulse is generated. Not only is the use of a bulky coupling capacitor avoided, but the stored charge dissipates in a much shorter time, thereby minimizing the "blind" interval in the sensing cycle.

Abstract: There is disclosed an improved pacer for controlling tachycardia. Following each tachycardia confirmation, a burst of a programmed number (e.g., 15) of stimulating pulses is generated. The rates of the bursts increase from cycle to cycle; thus following each tachycardia confirmation, a pulse burst at a different rate is generated. The rate of a burst which is successful in terminating tachycardia is stored, and following the next tachycardia confirmation the stored rate is used for the first burst which is generated. In this manner, there is a greater likelihood that tachycardia will be terminated following the first burst since a previously successful rate is used. Only if success is not achieved does scanning of the burst rate ensue, starting with the previously successful rate.

Abstract: There is disclosed an event counting and reporting heart pacer which is useful for patients who suffer from bradycardia. The pacer operates in a demand mode with a 2.5-second escape interval. A count is maintained of the number of pauses each of which exceeds this escape interval. Four successive pauses, each of which exceeds 2.0 seconds but is less than 2.5 seconds, are treated as a single 2.5-second pause. Following the detection of each pause, the escape interval is reduced to 1.2 seconds and the counter is inhibited from further operation; the counter is enabled and the 2.5-second escape interval applies once again only after a spontaneous heartbeat is detected within 1.2 seconds of the preceding beat. When a maximum count of 128 pauses is reached, the system thereafter operates with fixed 1.2-second escape interval.

Abstract: A pacer for controlling tachycardia, in which the coupled interval is scanned as well as the initial delay. The time parameters which are successful in terminating the condition are stored so that upon confirmation of another tachycardia event, the previously successful time parameters are the first ones to be tried. The unit also allows tachycardia to be induced by the physician so that the parameters which are programmable can be adjusted for optimum performance following a subsequent naturally occurring tachycardia confirmation.

Abstract: There is disclosed a dual chamber pacer which offers several advantages over prior art devices. Although the pacer requires for its operation AV delay and VA delay parameter values, most physicians characterize dual chamber pacers in terms of AV delay and ventricular pacing rate. The pacer of the invention can be programmed under external control by the physician setting values for the parameters with which he is most familiar. A subtractor in the pacer forms the difference between the reciprocal of the ventricular pacing rate and the AV delay to derive the value of the VA delay. The pacer is also characterized by active recharge of the atrial output capacitor so that a very short ventricular refractory period following atrial pacing may be provided. A single maximum rate timer prevents the generation of excessively fast ventricular stimuli, whether due to the ventricular or atrial sub-systems, or even if atrial contractions are being sensed at too rapid a rate.

Abstract: There is disclosed a pacemaker programmer for operation by a patient. The programmer can be pre-set by the physician to allow the patient to set his pacemaker in any one of a limited number of states, the states controllable by the patient being a sub-set of the set controllable by the physician with use of his conventional-type programmer. In the illustrative embodiment of the invention, while the physician programmer can control eight different rates, the patient programmer can set only three of these ("exercise", "awake" and "sleep" values), the particular values being preselected by the physician.

Abstract: A pacer which facilitates the measurements of both electrode impedance and stimulation threshold. When activated by an external magnet, a sequence of reducing-amplitude stimulating pulses is generated, with successive pulses in the sequence being separated by full-amplitude pulses. This pulse alternation scheme allows long test sequences, and therefore measurements with greater resolution, because full-amplitude pacing pulses are always present (even though at a slightly reduced rate). The reduction in amplitude of successive pulses is determined by the electrode impedance rather than being predetermined, and thus the examination of a skin potential recording allows electrode impedance to be determined along with the capture threshold.

Abstract: There is disclosed an improved implantable bone growth stimulator having a titanium, bullet-shaped case and pre-stretched helical electrode leads. The leads are sheathed, and the circuitry in the case is potted in silicone elastomer. The shape of the case lends itself to long-bone applications. The potting material is ideal for preventing ionic contamination of the circuit, while the metal case offers the requisite mechanical strength. The shape of the case facilitates removal during an explant procedure, and the pre-stretching of the leads prevents tissue damage at this time. The electrical circuit is a stacked assembly of components without a circuit board, which gives rise to the desired bullet shape of the case.