Ventricular repolarization sequences on the epicardium and endocardium. Monophasic action potential mapping in healthy pigs

To investigate repolarization sequence, monophasic action potentials were recorded from a mean of 153 ± 54 left and right ventricular epicardial and endocardial sites in 10 pigs using the CARTO mapping system (Biosense Webster, Waterloo, Belgium). The activation time and end-of-repolarization (EOR) time were measured and 3-dimensional maps of activation and repolarization sequences constructed.ResultsIn 8 of 9 pigs, both the activation and EOR times appeared first in the septum and last in the latero-basal areas on the endocardium, not on the epicardium. The EOR followed the activation sequence, both on the epicardium (in 8/9 pigs) and endocardium (in 8/8 pigs). The maximal EOR differences were 84 ± 20 ms, whereas the local EOR differences between paired sites against each other on the left ventricular epicardium and endocardium were 11 ± 9 ms in the apex and 12 ± 12 ms in the anterior wall.ConclusionThe EOR follows the activation sequence both on the epicardium and endocardium. The apico-basal gradients are predominant repolarization gradients, as compared with the epicardial–endocardial gradients.