Abstract: In cardiac signal processing apparatus, there is provided improved means for suppressing pacer signal artifacts, including both the discharge pulse and the recharge waveform (tail) of such artifact. Rate-limiting circuitry is used to substantially suppress the discharge pulse. However additional circuitry responsive to the detection of a pacer pulse is operative to obtain a measure of the electrical discharge of the discharge portion of the respective pacer pulse and to use such measure to generate a tail suppression signal which, when added to the original signal, substantially cancels the original pacer tail.A feed-back loop is opened by the rate-limiter when a pacer pulse occurs and in turn permits a large signal to be imposed on a threshold-level-type pacer pulse detector for connecting the large signal (pacer pulse) to a capacitor during the discharge portion of the pacer pulse.