GB1396365A - Heartbeat stimulating apparatus - Google Patents

Abstract

1396365 Heart pacemakers AMERICAN OPTICAL CORP 19 July 1972 [19 July 1971] 33825/72 Heading A5R [Also in Division H3] A heart pacemaker has a pulse generator providing stimulating pulses on electrodes E1, E2, the generator including means for varying the pulse width to automatically maintain the energy in each stimulating pulse at approximately a constant predetermined energy irrespective of power supply output variations. The pacemaker is of the type disclosed in Specification 1266907 but with the addition of components 100-103 and T100. A capacitor 57 charges up, unless the pacer is inhibited due to conduction of transistor T6 to discharge capacitor 57 until its potential is such that transistor T7 conducts and capacitor 57 discharges through resistor 37 and transistors T7 and T8 until the potential on capacitor 57 is insufficient to keep T7 conducting. Conduction of T7 and T8 results in discharge of capacitor 65 through transistor T9 and through the patients heart. The stimulating pulse width depends on how long transistor T7 is conducting which depends on -how rapidly capacitor 57 discharges. A resistor 103 monitors the battery supply output voltage and biases transistor T100 in dependence on this output. Capacitor 57 discharges partly through transistor T100, the effective resistance of which increases as the battery output decreases thereby increasing the stimulating pulse width with decreasing battery voltage to maintain the pulse energy approximately constant. The biassing of the transistors T7, T8 may be modified by using diodes (8, 10), Figure 2 (not shown), in the manner disclosed in Specification 1328926.