Abstract: Disclosed is a method and apparatus for discriminating pace pulse tails generated by signals discriminated from QRS complexes by mathematically ascertaining that the signal following the pace pulse peak has an exponential decay. The invention ascertains whether or not the waveform decays exponentially through application of a mathematical equation.

Abstract: Apparatus for classifying QRS complexes as dual chamber paced, atrially paced or ventricularly paced by assigning complexes to groups in accordance with shape, deriving the intervals between pace pulses and their respective QRS complexes, determining if the intervals for a given number of recent complexes from the group to which the current QRS complex is assigned are clustered, and classifying the current QRS complex by the correlation between the intervals of its pace pulses and the intervals of said clusters.

Abstract: Apparatus for effectively eliminating pace pulses from an ECG wave without introducing distortion comprising means for comparing the slope of the ECG wave with a threshold slope derived from the wave that is greater than the maximum slope produced in the wave by heart action and substituting values for a portion of the wave between first and second points on either side of the place in the wave where its slope exceeds the threshold value, the substituted values being interpolations of the value of the ECG wave occurring at said points. In a preferred embodiment means are provided for preventing the substitution from occurring unless a pace pulse is detected within a given distance of the said place in the ECG wave and means are also provided for setting said first point at a place in the ECG wave that occurs prior to a tail that precedes it.