It is unclear whether the right bundle branch block in this syndrome is real or whether it represents an early repolarization of right ventricular epicardium. The clinical and electrophysiologic data suggest that both possibilities exist. Some electrocardiograms clearly show a right bundle branch block after normalization of the ST segment (picture 9, panel C). There is frequently a prolongation of the H-V interval in these patients, which supports an abnormality of the conduction system. On the other hand, we can find electrocardiograms without right bundle branch block after normalization of the ST segment elevation (picture 10). Moreover, not all the patients have a prolongation of the H-V interval.

Approximately 10% of patients with this syndrome suffer from paroxysmal atrial fibrillation. It is possible that similar genetic defects alter atrial and ventricular electrophysiology in some patients.

The polymorphic ventricular tachycardia can be often reproduced by programmed electrical stimulation of the heart in these patients, suggesting a re-entrant mechanism. Phase 2 re-entry is believed to undelie ventricular arrhythmias in this syndrome.