Cardiac pacer circuit

An electronic circuit for a cardiac pacer comprising, in combination:

• a. an astable multivibrator for normally generating a series of pulses of predetermined duration at a desired rate, unless reset prior to completion of their generation;
• b. electrode means electrically coupled to said astable multivibrator and adapted to be surgically implanted on the heart of a patient;
• c. a difference amplifier having first and second input terminals and an output terminal;
• d. means connecting said electrode means to said first and second input terminals for amplifying the R-wave signal produced during normal ventricular contractions of the heart of a patient;
• e. a bandpass active filter connected to said output terminal of said difference amplifier for attenuating the signals from said amplifier which fall outside of a predetermined frequency band;
• f. a level detecting circuit connected to receive the output from said bandpass active filter for generating a trigger pulse when the output from said bandpass active filter exceeds a predetermined threshold;
• g. a monostable multivibrator circuit connected to the output of said level detector circuit for producing a pulse of predetermined duration greater than the inherent recovery time of said difference amplifier each time said level detector produces a trigger pulse;
• and
• h. means connecting the output of said monostable multivibrator circuit to said astable multivibrator for resetting same to an initial condition each time said monostable multivibrator circuit produces a pulse.