Biventricular pacing and transmural dispersion of the repolarization

In 2003, Medina-Ravell et al .1 published a study that suggested that biventricular pacing could be arrhythmogenic in a subset of patients because of the reversal of the normal endocardial-to-epicardial activation sequence by left-ventricular epicardial pacing. As epicardial action potentials are briefer than endocardial action potentials, transmural dispersion of the repolarization (TDR) is larger with an epicardial-to-endocardial activation sequence than with an endocardial-to-epicardial activation sequence. Medina-Ravell et al . demonstrated this in an isolated arterially perfused rabbit left-ventricular wedge preparation. They also showed, in a quasi-ECG derived from this preparation, that TDR was faithfully reflected by the T peak-end interval and that T peak-end was larger with epicardial pacing than with endocardial pacing of the preparation. Their conclusion that a similar effect occurs in intact hearts in humans was substantiated by …