Unusual capture of a capture beat : Lessons learned from the 12-lead electrocardiogram.

In a 63-year-old woman, several capture beats were documented during a slow, right bundle-branch block tachycardia. These occur whenever retrograde conduction is lacking due to ventriculoatrial Wenckebach block. The 12-lead electrocardiogram suggested a ventricular origin in the area of the left posterior papillary muscle which was confirmed by endocardial activation mapping. The focal ventricular tachycardia was successfully ablated, and the patient has remained arrhythmia-free during follow-up.