Stepwise Anatomical Approach to Ablation of Intramural Outflow Tract Ventricular Arrhythmias Guided by Septal Coronary Venous Mapping

Background: Intramural site of origin is a major cause of ablation failure of ventricular arrhythmias and the optimal strategy is unclear. This study investigated the efficacy of a stepwise ablation approach for intramural outflow tract (OT) premature ventricular complexes (PVCs) guided by mapping of the septal coronary venous system. Methods: Consecutive patients with OT PVCs were included in which an intramural origin was confirmed by demonstration of earliest activation in a septal coronary vein. Radiofrequency ablation was performed from the closest endocardial site in the left (LVOT) and/or right ventricular OT (RVOT) independent of the local activation time. If there was no suppression by endocardial ablation, retrograde transvenous ethanol infusion with a single or double balloon technique was performed, targeting the earliest septal coronary vein. If venous anatomy was not suitable for ethanol ablation or if this failed, bipolar ablation was performed. Results: Sixty patients (age 61±12 years, 78% male) were included. The mean QRS duration of the PVC was 150.8±17.6 ms with a maximum deflection index of 0.51±0.11, and the most common ECG pattern was a left bundle branch block with inferior axis and V3 transition (63%) followed by a right bundle branch block with inferior axis and no transition (27%). Earliest ventricular activation (28.6±11.2 ms pre-QRS) was recorded in the left ventricular annular vein in 15 cases and a septal perforator vein in 45 cases. Acute PVC suppression at the end of the procedure was achieved in all cases. In 87% of cases (n=52), endocardial ablation from the endocardial LVOT, RVOT or both was successful in eliminating the PVC. In the remaining 8 patients, the PVC was eliminated with ethanol infusion (n=7) and bipolar ablation (n=1). Complications included one case of pericardial effusion related to venous mapping. During follow-up (17±24 months), the PVC burden was reduced from 28±12% to 2.3±4.7% and long-term success (≥80% burden reduction) was 88%. Conclusions: Most intramural OT PVCs can be successfully eliminated with endocardial ablation adjacent to the earliest intramural activation site. A high success rate is achieved when following a stepwise approach, with bailout ablation strategies required in a minority of cases.