Apparatus for graphical representation of a train of ECG complexes each including an R wave and a T-P interval and having variable isoelectric levels. The apparatus includes an isoelectric alignment unit for aligning the complexes in terms of isoelectric level by aligning respective T-P intervals, thereby to provide a graphical representation of the train of ECG complexes and a temporal alignment unit for aligning the complexes temporally using a selected point on the respective R waves. The aligned units are superimposed to provide a distribution of a normalized ECG signal over a series of pulses or heartbeats.
