Preexcitation unmasks J waves: 2 cases

It is not known if J waves of early repolarization can be affected by depolarization or not. We report 2 cases in whom J waves were unmasked by preexcitation. A 59-year-old woman with Wolff-Parkinson-White syndrome who had frequent episodes of tachycardia underwent radiofrequency catheter ablation. The 12-lead electrocardiogram on admission showed delta waves and a notch in leads II, III, and aVF (J waves), which disappeared after the elimination of preexcitation. A 56-year-old man with Wolff-Parkinson-White syndrome was admitted for catheter ablation for supraventricular tachycardia. His electrocardiogram showed delta waves in I, II, aVL, V 2 to V 6 , and J waves in the inferior leads and V 3 through V 6 with ST elevation and ST elevation in V 2 . After ablation, J waves disappeared and were replaced by S waves. However, ST elevation remained in the precordial leads. The 2 cases suggest that J waves may be affected by the depolarization process: preexcitation.