Comparison of the Ventricular Tachycardia Circuit Between Patients With Ischemic and Nonischemic Cardiomyopathies

Abstract

Background: There has been increasing awareness of the 3-dimensional nature of ventricular tachycardia (VT) circuits. VT circuits in patients with ischemic cardiomyopathies (ICM) and non-ICM (NICM) may differ in this regard. Methods: Among patients with structural heart disease and at least 1 hemodynamically tolerated VT undergoing ablation, we retrospectively analyzed responses to all entrainment maneuvers. Results: Of 445 patients (ICM 228, NICM 217) undergoing VT ablation, detailed entrainment mapping of at least 1 tolerated VT was performed in 111 patients (ICM 71, NICM 40). Of 89 ICM VTs, the isthmus could be identified by endocardial entrainment in 55 (62%), compared with only 8 of 47 (17%) NICM VTs ( P <0.01). With combined endocardial and epicardial mapping, the isthmus could be identified in 56 (63%) ICM VTs and 12 (26%) NICM VTs ( P <0.01), whereas any critical component (defined as entrance, isthmus or exit) could be identified in 76 (85%) ICM VTs and 37 (79%) NICM VTs ( P =0.3). Complete success (no inducible VT at the end of ablation, 82% versus 65%, P =0.04) and 1-year, single-procedure VT-free survival (82% versus 55%, P <0.01) were both higher among patients with ICM. Conclusions: Among mappable ICM VTs, critical circuit components can usually be identified on the endocardium. In contrast, among mappable NICM VTs, although some critical component can typically be identified with the addition of epicardial mapping, the isthmus is less commonly identified, possibly due to midmyocardial location.