Abstract: In heart monitoring systems for use with patients whose hearts may be stimulated by an artificial pacer and which system includes heart rate indicating means, there is provided circuitry for suppressing the recharge waveform portion of a pacer signal artifact in addition to suppression of the discharge pulse portion of the signal artifact, thereby to prevent inaccuracies in the heart rate indication arising from the pacer signal artifact. In addition to suppressing the discharge pulse portion of a pacer signal artifact with conventional means, the invention recognizes that the recharge waveform of the pacer signal may cause a false impression of a QRS complex which actuates heart rate indicating means and provides novel circuitry for suppressing such recharge waveform.