Electrocardiographic characteristics and mapping approach of ventricular arrhythmias originating from the left ventricular summit.

The left ventricular summit is the most common site of idiopathic epicardial ventricular tachycardia (VT). We report a case of a 48-yr-old lady who presented with VT of RBBB configuration, inferior axis and delayed initial activation. During electrophysiological study, local activation in the distal great cardiac vein (GCV) preceded surface QRS by 56 ms whereas mapping in the aortic sinuses and left ventricular outflow tract endocardially revealed late activation. Ablation in the distal GCV with an irrigated catheter successfully terminated the tachycardia. The 12‑lead electrocardiogram is an invaluable tool for predicting the VT focus and planning the mapping strategy.