GB1482281A - Electrical generator - Google Patents

Abstract

1482281 Implantable pacemakers COR ATOMIC INC 25 June 1974 [12 July 1973 (2)] 28188/74 Heading A5R [Also in Division H1] An implantable pacemaker, Fig. 3, comprises a power source and circuitry generating pacer pulses on demand, assembled via common housing. The sealed power source 23 consisting of a shielded nuclear heat source and thermopile, described in detail in Division H1, is cradled on shaped printed circuit boards 25, 27 on which are mounted transformer 35, magnetic switch 33, capacitor 31 and solid state circuit package 29 in a titanium shell 43, with a welded-on lid. With the output assembly, consisting of flexible connector 272 attached to output lead 263 gas-tightly sealed via ceramic sleeve 267 in flanged sleeve 261 and surrounded by ferrite RF filter 265, in position resilient neutron absorbent potting rubber 41 is injected into the shell and sleeve 261 welded in position in organ. Connector 272 is then connected to terminal block into which a dummy catheter surrounded by suture boot 283 is inserted and the assembly moulded in epoxy resin 50 so as to leave dimple 51 flush with its surface for earthing to the ribs or skin between which the pacer is implanted. The circuitry, Fig. 13, consists of a multivibrator delivering 1.1 mS 8 mA pacer pulses at a nominal rate of 70 per minute unless inhibited by natural R waves from the heart, or at a rate of 85 when noise interference masks the normal Q-R-S heart complex. This higher rate is chosen to minimise competition with the normal heart rate when in normal rhythm. Amplifier 303 amplifies natural R waves, pacer pulses and noise to trigger generation by monostable 305 of .275 sec square pulses the leading edges of which reset multivibrator 311 to deliver a pulse after 850 mS. During the square pulse monostable 305 cannot be triggered thus preventing stimulation during T wave onset and delay. Noise rate turn-on 307 monitors the output of amplifier 303 and disables it on detecting noise so that no resetting pulses are applied to multivibrator 311, which then produces pacer pulses at the higher rate. The pacer can be made to deliver such pulses even during normal heart functioning to enable a physician to check its operation by using a magnetic external of the body to close, switch 33. The sensitivity of amplifier 303 is so chosen that it responds to R waves but not to abnormal P waves.