Cardiac repolarization activity can be mapped using action potential duration (“APD”) and/or activation recovery interval (“ARI”). APD can be measured using a bipolar electrogram signal measured, for example, using a monophasic action potential (“MAP”) catheter. ARI can be measured using unipolar electrogram signals. The electrogram signal is used to identify a depolarization tick time. A repolarization tick time can be identified using either a point in time when the electrogram signal passes below a threshold or via local maxima and minima of a first derivative of the electrogram signal. Diastolic intervals can also be computed using depolarization and repolarization tick times.
