Abstract
A 32-year-old male received catheter ablation of frequent ventricular extrasystoles (VEs). His electrocardiogram showed monomorphic VEs with an inferior axis and early precordial transitional zone. During electrophysiological testing, a 10-pole catheter positioned in the left ventricular outflow tract recorded sharp pre-potentials just before the ventricular activation during VEs as well as sinus beats. Three-dimensional mapping was performed by annotating the sharp pre-potentials to reveal that the earliest activation site was deemed to be close to the left anterior fascicle. A cryoablation catheter was introduced into the left ventricle and freezing for 240 seconds successfully eliminated the clinical VEs without any complications.