GB1397290A - Heart pacers - Google Patents

Abstract

1397290 Heart pacemakers AMERICAN OPTICAL CORP 6 Dec 1972 [6 Dec 1971] 56402/72 Heading A5R [Also in Division H3] A heart pacemaker has first timing means 10 for generating a stimulating pulse on atrial terminals E3, E4 at the end of a first time interval, means 20 for adjusting the first timing interval, second timing means 32, 36 for generating a stimulating pulse on ventricular terminals E1, E2 at the end of a second time interval commencing at the generation of a pulse on terminals E3, E4, means 34 for adjusting the second time interval, a ventricular beat detector 14 operative to inhibit generation of ventricular stimulating pulses and operative to reset the first timing means 10 and means 30 for resetting the first timing means 10, at the end of a third time interval commencing at the application of an atrial stimulating pulse on terminals E3, E4, the third time interval being longer than the maximum second time interval. Atrial pulses are generated by generator 10 at a rate set by variable resistor 20, each pulse generated causing triggering of a fixed 260 m sec one-shot 30 and of a variable 50 to 250 m sec one-shot 32. At the end of the 260 m sec delay one-shot 30 resets a timing circuit of generator 10 which if, for example, set to give 75 p.p.m. then generator on atrial pulse 540 m sec after the reset. Generator 10 is also reset if detector 14 detects a natural or stimulated ventricular beat but such resetting does not affect the atrial pulse timing except in abnormal circumstances when a ventricular beat may occur after the 260 m sec delay of one-shot 30 lapses; in the latter case the next atrial pulse occurs 540 m sec after. reset of generator 10 by the abnormal ventricular beat instead of 540 m sec after reset by one-shot 30. 50 to 250 m sec, as selected by adjustment of a resistor 34, after triggering of one-shot 32 by generation of an atrial pulse, one-shot 32 triggers generator 36 to produce a ventricular, stimulating pulse unless a timing circuit in generator 36 is reset, and the generator thus inhibited, in response to detection of a ventricular beat during the atrial ventricular delay determined by oneshot 32. Controls 20 and 34 allow independent adjustment of the pacing rate and A-V delay. Specification 1307912 and 1335679 are referred to.