Heterogeneous distribution of electrophysiological behavior across the heart is essential for normal cardiac function. If this heterogeneity becomes excessive it may contribute to arrhythmogenesis and sudden cardiac death. Controversy exists regarding the localization of activation and repolarization gradients in the diseased heart and how these heterogeneities contribute to arrhythmogenesis. In this review we focus on the genesis and existence of transmural heterogeneity in activation and repolarization. We will describe a possible embryonic origin of these heterogeneities and address the question how heterogeneities contribute to the genesis of the electrocardiogram and how they may cause reentrant arrhythmias. This review subsequently concentrates on several pathologies in which transmural heterogeneities are thought to play a role.
Keywords: Action potential duration; Activation; Embryology; Purkinje network; Repolarization.
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