Figure 2.

Exercise induced ventricular fibrillation. This is an ECG of a 13 year old girl who had syncope while running. During a treadmill exercise test, bigemini involving right bundle branch block and rightward axis (empty circle) and left bundle branch block, inferior axis type, premature ventricular contraction (filled circles) were induced (left panel). Ventricular fibrillation was induced after left bundle branch block type premature ventricular contraction. Several of the premature beat morphologies appear somewhat different because of the fusion of the sinus beat.