Catheter Ablation of Ventricular Arrhythmia in Non-Ischaemic Cardiomyopathy: Anteroseptal versus Inferolateral Scar Sub-Types

Background —The aim was to relate distinct scar distributions found in non-ischaemic cardiomyopathy (NICM) with ventricular tachycardia (VT) morphology, late potential (LP) distribution, ablation strategy and outcome. Methods and Results —Eighty-seven patients underwent catheter ablation for drug-refractory VT. Based on endocardial unipolar voltage, 44 were classified as predominantly anteroseptal (AS) and 43 inferolateral (IL). AS patients more frequently fulfilled diagnostic criteria for dilated cardiomyopathy (64% versus 36%), associated with more extensive endocardial unipolar scar (41 (22-83) versus 9 (1-29) cm2, p<0.001). Left inferior VT axis was predictive of AS scar (PPV 100%) and right superior axis for IL (PPV 89%). LPs were infrequent in the AS group (11% versus 74%, p<0.001). Epicardial LPs were common in the IL group (81% versus 4%, p<0.001) and correlated with VT termination sites (K=0.667, p=0.014) whereas no AS patient had an epicardial VT termination (p<0.001). VT recurred in 44 patients (51%) during a median follow-up of 1.5 years. AS scar was associated with higher VT recurrence (74% versus 25%, log-rank p<0.001) and redo procedure rates (59% versus 7%, log-rank p<0.001). After multivariable analysis, clinical predictors of VT recurrence were electrical storm (HR 3.211, p=0.001) and NYHA class (HR 1.608, p=0.018); the only procedural predictor of VT recurrence was AS scar pattern (HR 5.547, p<0.001). Conclusions —Unipolar low voltage distribution in NICM allows categorization of scar pattern as IL, often requiring epicardial ablation mainly based on LPs, and AS which frequently involves an intramural septal substrate, leading to a higher VT recurrence.