Left ventricular epicardial outflow tract tachycardia - A new distinct subgroup of outflow tract tachycardia

The present study investigated the incidence and ECG characteristics of ven tricular tachycardias (VTs) originating from the left ventricular (LV) epic ardium. Thirty-one consecutive patients with VT or premature ventricular co ntraction originating front the outflow tract (OT-VT) underwent catheter ab lation. Twenty-one OT-VTs were ablated from the endocardium in the right ve ntricular (RV) OT and 3 were ablated from the endocardium in the LVOT. In t he remaining 7 patients, 4 (13%) OT-VTs were LV epicardial in origin, and 1 of these was ablated from the left sinus of Valsalva. The ECG characterist ics of OT-VT of epicardial origin included prominent call R-waves in the in ferior leads, an R-wave in V-1 and an S-wave in V-2, precordial R-wave tran sition in V2-4, a deep QS-wave in aVL, and no S-wave in V-6. In addition, t here was an atypical left bundle branch block morphology with an inferior a xis. These findings were observed during pacing from several sites in the L V epicardium. Furthermore, pacing from the left sinus of Valsalva caused a relatively tall R in V-1, deep S-wave in V-2 and a tall R-wave with a shall ow S-wave in V-3, as well as tall R-waves in the inferior leads, which repr esented intermediate characteristics between RV endocardial OT-VT and LV en docardial OT-VT. In conclusion, OT-VT originating from the LV epicardium is not uncommon and has characteristic ECG findings. Some of them can be abla ted from the left sinus of Valsalva.