Electrophysiology Study
The electrophysiology study (EPS) was performed in 92 out of 138 patients (66.7%). Baseline measurements of conduction intervals and programmed ventricular stimulation were recorded. The programmed ventricular stimulation (PVS) was performed on two sites (right ventricular apex and right ventricular outflow tract, unless the patient had inducible ventricular tachycardia at the first location), with energy of twice the diastolic threshold, using two drive cycles (S1: 600 and 430 ms) up to 3 extra stimuli (S2 to S4) with 200ms as the shortest coupling time. The EPS result was considered positive if sustained VF or VT was induced.14 Ventricular effective refractory period (VERP) was defined as the longest S1-S2 interval that fails to achieve ventricular capture. If there was conduction under 200ms, VERP was defined as “less than 200ms”.10