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.