Epicardial activation increases transmural dispersion of repolarization in a heterogeneous model of wild-type and short QT mutant tissue

This computational study investigates the effects of epicardial stimulation on healthy and mutant excitable tissue. A heterogeneous wild-type (WT) model of human ventricular electrophysiology and a modified version simulating short QT (SQT) syndrome were used. The utilized anisotropic anatomical structures were both a slice cut out of a human left ventricular geometry and a beam from endocardium to epicardium extracted from this slice. Epicardial pacing increased the transmural dispersion of repolarization (TDR) in WT and SQT mutant tissue. The QT time was prolonged in WT tissue but stayed nearly constant in SQT affected tissue. In the slice anatomy, intra-ventricular dispersion of repolarization overweights TDR. TDR was increased nearby the electrode but reduced in tissue opposite to the electrode. We assume, that during epicardial pacing the risk for arrhythmic events is increased but not higher in patients affected by the SQT syndrome compared to healthy patients