Demand heart pacer

A demand heart pacer which includes an oscillator, an amplifier for receiving and amplifying naturally occurring heart pulses, a monostable multivibrator activated by amplified naturally occurring heart pulses to generate a disabling pulse, and means for disabling the oscillator upon occurrence of a disabling pulse is of complimentary metal oxide semi-conductor devices to present a capability of operating with low power dissipation to facilitate implantable heart pacer use having an enhanced power supply lifetime. The heart pacer produces stimulation pulses in an 'inhibit mode' at a first frequency and stimulation pulses in a 'fixed rate mode' at a second frequency, the difference in the first and second frequencies being indicative of the power supply voltage to provide a monitor of its state or condition. The heart pacer additionally employs an oscillator inhibitor, which includes a field effect transistor biased to a level which is increased upon reception of high frequency noise, to prevent conduction, and which additionally operates to define a variable second half of a refractory period to distinguish noise at a frequency approximately twice that of an acceptable heartbeat frequency. (Auth.)