Bipolar Ablation of the Interventricular Septum is More Efficient at Creating a Transmural Line than Sequential Unipolar Ablation

INTRODUCTION: Post infarct ventricular tachycardia (VT) often involves the interventricular septum (IVS) and requires transmural septal ablation. The purpose of this study was to compare the efficacy of bipolar ablation (BIA) versus sequential unipolar ablation (SUA) in creating a transmural ablation line along the IVS scar border. METHODS AND RESULTS: Both ablation strategies were compared in a phantom agar model first and then in 10 post infarct sheep. In the phantom agar model BIA lesions were larger, transmural, and less dependent on catheter alignment and contact compared with SUA. Noncontact mapping was used in the animals to identify the septal scar border and create a 30-mm ablation line. In five animals BIA (50 W) was performed between two irrigated catheters on either side of the IVS, and in five control animals SUA (50 W) was performed, first on the left ventricle (LV) septal scar border and then on the opposing right ventricle (RV) septal surface. Electrical block along ablation lines was confirmed with noncontact mapping. BIA required significantly less ablations (12 + or - 1 vs 29 + or - 7, P = 0.001), ablation time (22 + or - 3 vs 48 + or - 6 minutes, P < 0.001), and energy (58 + or - 7 vs 124 + or - 21 kJ, P < 0.001). At pathological examination all ablation lines in both groups were transmural at the IVS border. BIA endocardial ablation lines (LV + RV) were significantly longer than SUA lines (76 + or - 10 vs 49 + or - 11 mm, P = 0.003). CONCLUSION: BIA of the IVS is highly effective at creating a transmural ablation line, requiring less ablation and creating longer lesions than SUA. BIA ablation may have a role for post infarct VT involving the IVS.