Catheter ablation for ventricular tachycardia after failed endocardial ablation: Epicardial substrate or inappropriate endocardial ablation?

BACKGROUND The substrate of myocardial ventricular tachycardia (VT) may involve the subepicardial myocardium. OBJECTIVE The purpose of this study was to assess the incidence of epicardial substrates in patients with a previously failed endocardial ablation attempt for VT as well as the safety and effectiveness of epicardial ablation. METHODS Using an electroanatomic mapping system, endocardial and epicardial maps were acquired. Irrigated radiofrequency current ablations of all inducible VTs were performed. RESULTS Between 2005 and 2009, 59 patients with or without structural heart disease underwent epicardial VT ablation. Pericardial access failed in 3 (5%) of these patients. Of the remaining 56 patients, an epicardial substrate was found in 41 (73%). Overall, acute success was achieved in 46 (78%) of 59 patients, with complete VT abolition in 27 (46%) and partial abolition in 19 (32%). Successful outcomes were the result of endocardial ablation only in 14 (24%) patients, epicardial ablation in 21 (36%), and endocardial/epicardial in 11 (19%). Ablation failed to prevent reinduction in 8 (13%) patients, and VTs were noninducible prior to ablation in 5 (8%). Two periprocedural deaths occurred, one after right ventricular perforation and one due to electromechanical dissociation. Hepatic bleeding occurred in two patients. Recurrence of any VT occurred in 27 (47%) of 57 surviving patients during median follow-up of 362 days (q1-q3; 180-468 days). Repeat epicardial mapping was not feasible due to adhesions in 3 (25%) of 12 patients. CONCLUSION In patients with a previously failed endocardial VT ablation, epicardial mapping reveals a VT substrate in nearly three fourths of all patients, and epicardial ablation is required for successful VT abolition in more than half of patients. However, life-threatening complications may occur. Repeat epicardial access was not possible in 25% due to local pericardial adhesions.