GB1356190A - Heart stimulators - Google Patents

Abstract

1356190 Heart stimulator AMERICAN OPTICAL CORP 14 Sept 1971 [14 Sept 1970] 42852/71 Heading A5R A heart stimulator for treating "paroxysmol supraventricular tachycardia", a sudden attack of rapid heart action, comprises a pulse generator for supplying a burst of electrical stimuli at a continually changing rate above 160 pulses per minute. The stimulator comprises a reed switch 32, with a reed 31 movable by a manually manipulable magnet from a "normal" position as shown in Fig. 2, to an operational position in which it contacts the terminal 29. In the "normal" position a capacitor 28 is charged by batteries 3 to 7, via a resistor 23, whilst a further capacitor 65 is charged by the batteries via resistor 24, electrodes E1 and E2, the heart 14 and the return path to the battery 3. When the reed 31 engages the terminal 29 the capacitor 28 discharges through diodes 27 and 28, and a resistance 25, and also through resistors 35 and 37, capacitor 57, and resistors 61 and 63, whereby the capacitor 57 is charged. When the potential of the emitter of a transistor T7 exceeds that at its base by approximately ¢ volt, the capacitor 57 discharges through the transistor T7 and a further transistor T8 and resistors 61 and 63 until the difference between the potential of the emitter and base of transisor T7, no longer renders the transistor conducting, whereby the capacitor 57 is once more charged from capacitor 28. During each oscillation an increased potential is produced at the base of a transistor T9 due to the discharging of capacitor 57, and this transistor is allowed to conduct causing the capacitor 65 to rapidly discharge through the heart. A typical frequency of oscillation is said to be 1000 cycles/minute.