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Figure 5 A shift from endocardial to epicardial pacing prolongs QT (A) and transmural dispersion of repolarization (B) and permits propagation of early afterdepolarizations (EADs) in an arterially perfused rabbit left-ventricular wedge preparation. Dofetilide (5 nmol/l) led to the appearance of phase 2 EADs in endocardium (Endo). The EADs failed to propagate across the ventricular wall during endocardial pacing (A), but succeeded during epicardial (Epi) pacing, generating R-on-T extrasystoles (B). ECG = electrocardiogram. Modified and reprinted, with permission, from Medina-Ravell et al. (4). Abbreviations as in Figure 3.