Polymorphic ventricular tachycardia in a model of triggered cardiac activity

It has been suggested that the cardiac arrhythmia known as torsades de pointes could be caused by competing foci of triggered activity. To examine this competitive triggering hypothesis, we used a model of ventricular action potential propagation to simulate two separate zones of heterogeneous myocardium under electrophysiologic conditions that have been correlated with the occurrence of torsades de pointes. We found that the two zones could trigger competitively, and that the corresponding electrogram morphology alternates as observed during episodes of torsades de pointes. These preliminary results are in accord with the competitive triggering hypothesis