Telectronics Pty. Limited

Stephen J Swift

Tibor A Nappholz

David K Money

Roworth A Spurrell

Michael S Hirshorn

Ronald C Bradbury

Alan J Camm

Andrew D MacLaurin

Robert J Evans

John G Frost

The signal sensed on a heart pacer electrode is converted by a delta modulator to a sequence of samples of 0 and 1 bit values. The resulting bit sequence is delayed, and the original bit sequence and its delayed version are continuously subtracted from each other in a clocked up/down counter to derive a count. When the count reaches a threshold value, three different recognition logic circuits are triggered and they then operate for two milliseconds. One circuit recognizes a beat if the count does not drop below another, lower threshold value during the timing interval. A second circuit detects a beat if the count remains above the threshold level for at least 50% of the time during the timing interval. The third circuit detects a beat by operating directly on the delta modulator output bit sequence; it checks whether bits of the value indicative of the triggering event predominate over bits of the opposite value during the timing interval.

Physiological event recognition techniques for use with a delta modulator

A tachycardia control pacer for which 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, resets two scanned inter-pulse 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 the previously retained successful values would otherwise progress to the programmed values.

Externally controlled tachycardia control pacer

Externally-inhibited tachycardia control pacer

A heart pacer in which the magnitude of the end-of-life test current source is programmable. This effectively allows the physician to program the condition which will control a switch-over to end-of-life operation. It also allows the physician to override end-of-life operation after it initially takes place following a failing of the end-of-life test. The pacer also includes an additional end-of-life test involving the continuous monitoring of the supply potential and a switch-over to end-of-life operation should the pacer powering potential momentarily fall below a threshold level.

Heart pacer end-of-life detector

A tachycardia control pacer in which at least one scanned pulse is generated following each tachycardia confirmation, and the last-used pulse timing is retained following the next tachycardia termination for subsequent first use following the next tachycardia confirmation. The tachycardia termination detecting circuit does not respond to the time interval between at least the first two heartbeats following a generated pulse, to prevent a false determination of tachycardia termination due to the excessive pauses which sometimes occur immediately after pacing despite the fact that tachycardia has not terminated.

Tachycardia control pacer with improved detection of tachycardia

There is disclosed an implantable bone growth stimulator whose direct-current output can be monitored. Rather than to interrogate the device, e.g., by using a control magnet as in the heart pacer art, the device continuously transmits pulses of electromagnetic energy at a rate proportional to the current being delivered. The continuous transmission expends no more than about five percent of the total power. Instead of using an electrode lead as an antenna for radiating the pulses, a separate coil inside the device is utilized so that the therapeutic current itself is in no way affected by the pulse transmission. Effective transmission is achieved despite the fact that the device is hermetically sealed in a titanium case. Also included is an electronic switch for drastically limiting power drawn from the battery until implantation takes place, in order to provide an extended shelf life.

Monitorable bone growth stimulator

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.

Externally-reset tachycardia control pacer

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.

Variable length scanning burst tachycardia control pacer

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.

Scanning burst tachycardia control pacer

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.

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Hornsby, Australia

Stephen J Swift