Patent GB-1410743-A (GB)
Title: Cardiac pacemaker monitoring system
IPC: A61B5/366
Filed: 1973-02-14
Abstract: 1410743 Electro-medical apparatus F HOFFMANN-LA ROCHE & CO AG 14 Feb 1973 [25 Feb 1972 (2)] 7351/73 Heading G1N In a cardiac pacemaker monitoring system, ECG and pacemaker spike signals are derived from a pacemaker carrying patient 21, a QRS pulse is derived from the ECG signal in each cardiac cycle, a predetermined time interval is established from the onset of a pacemaker spike, and an indicator 38 is operated, to denote occurrence of a capture event (i.e. production of a QRS pulse by a pacemaker spike), by a pulse produced if the QRS pulse occurs within the predetermined time interval. A second indicator 37 is also provided to indicate non-capture events. As shown, ECG signals from pick-up electrodes 11 are applied to a QRS detector 23 and a pacemaker spike detector 27. Timing logic 24 receives the QRS pulse from detector 23 and provides a plurality of timing signals D1, D2, P and C, Figs. 2 and 3 (not shown). A spontaneous heartbeat detector 25 provides an output to an indicator 26 upon occurrence of spontaneous QRS pulses, inputs A and G inhibiting detector 25 upon occurrence of capture events. The pacemaker spike detector 27, Figs. 4-7 (not shown), processes the ECG signals to provide spike signals which are applied to a threshold detector, the threshold of which is derived from an integrator which also receives the spike signals. The threshold detector provides a pulse for each spike which exceeds the threshold, these pulses being applied to a pulse width discriminator circuit and a pulse rate discriminate circuit to provide normalized pulses representing pacemaker spike signals. The system may be used to monitor fixed rate and demand ventricular pacers, fixed rate and demand atrial pacers, and fixed rate and demand atrial-ventricular pacers. Switches throughout the system are set for the appropriate type of pacer, Fig. 8 (not shown). Pulses from detector 27 are applied via a toggle switch, a NAND gate 29 and a repetition rate discriminator 32 or toggle switch 28, a NAND gate 31 and a repetition rate discriminator 33 depending on whether they are ventricular pacer pulses or atrial pacer pulses respectively. Three channels are provided, a ventricular pacing channel 34, Fig. 9 (not shown), an atrial-ventricular pacing channel 35, Fig. 11 (not shown), and an atrial pacing channel 36, Fig. 12 (not shown). For ventricular pacing, a capture event is indicated at 38 if a QRS pulse falls within 0-300 ms of a ventricular pacer pulse by delaying the pacer pulse by 300 ms and detecting if a pulse D1 of 300 ms from the logic 24 occurs simultaneously with the delayed pulse. Non-simultaneous occurrence causes a pulse to be applied to non-capture indicator 37 and to an alarm indicator 39 via logic 41. For atrial pacing, a capture event is indicated at 38 if a QRS pulse falls within 120-275 ms of an atrial pacer pulse by delaying the pacer pulse by 275 ms and detecting if the delayed pulse and a pulse D2 of 155 ms from logic 24 occur simultaneous. Non simultaneous occurrence again causes a pulse to be applied to indicator 37 and indicator 39 via logic 41. For atrial-ventricular pacing, an atrial-ventricular capture event is indicated at 38 if a ventricular pacer pulse occurs within 120-250 ms of an atrial pacer pulse in similar manner to above. Capture of a QRS pulse by the ventricular pacer pulse is also indicated in channel 34. The alarm indicator is energized by logic 41, Figs. 14 and 15 (not shown), only if three non- capture events are detected within any period of 6 seconds.