Endocardial and epicardial radiofrequency ablation of ventricular tachycardia associated with dilated cardiomyopathy: The importance of low-voltage scars

Objectives The purpose of this study was to evaluate the occurrence, locations, and relationship of ventricular tachycardia (VT) to low-voltage areas in dilated cardiomyopathy (DCM). Background The substrate causing monomorphic VT after infarction is characterized by regions of low-voltage (<1.5 mV) scar on electroanatomic maps. The substrate causing VT associated with DCM is less well defined. Methods A total of 28 patients were studied with endocardial (26 patients) and epicardial (8 patients) electroanatomic mapping. The VT circuits were defined by entrainment or pace mapping. Results Ventricular tachycardia was due to focal VT in 5, bundle-branch re-entry in 2, and myocardial re-entry in 22 patients (both focal and re-entry VTs in 1 patient). All patients with myocardial re-entry had endocardial (20 of 20 patients) and/or epicardial (7 of 7 patients mapped) scar. Most (63%) endocardial scars were adjacent to a valve annulus. Of the 19 VT circuit isthmuses identified, 12 were associated with an endocardial scar and 7 with an epicardial scar. All myocardial re-entrant VTs were abolished in 12 of 22 patients, and inducible VT was modified in 4 patients. During follow-up of 334 ± 280 days, 54% of patients with myocardial re-entry were free of VT despite frequent episodes before ablation. Conclusions The VTs in DCM are most commonly the result of myocardial re-entry associated with scar. Scars are often adjacent to a valve annulus, deep in the endocardium, and can be greater in extent on the epicardium than on the endocardium. The use of epicardial mapping and radiofrequency is likely to improve success.