Catheter ablation of ventricular tachycardia in nonischemic cardiomyopathy with near-normal left ventricular ejection fraction.

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Patients with idiopathic nonischemic cardiomyopathy (NICM) and near-normal left ventricular ejection fraction (LVEF) may develop ventricular tachycardia (VT). The purpose of this study was to describe procedural characteristics and outcomes in patients requiring ablation for NICM-related VT with near-normal LVEF compared to impaired LVEF. Over 8 years, 77 consecutive patients with NICM-related VT underwent catheter ablation. Of these patients, 47 had idiopathic NICM (20 near-normal LVEF, 27 impaired LVEF). Procedural characteristics and outcomes were compared. Mean age was 64 ± 12years, mean LVEF was 40% ± 14%, and 75% were male. In the near-normal LVEF group compared to the impaired LVEF group, LVEF was higher (54% ± 5% vs 30 ± 8%; P<.001), scar was predominantly located in the perivalvular left ventricle (LV) and basal septum (15/20 [75%]), was smaller in size [bipolar: 9.7 (6.2-32.4) cm2 vs 30.4 (21.1-37.6) cm2, P=.03; unipolar: 23.3 (6.6-39.9) cm2 vs 57.2 (42.2-74.9) cm2, P = .009], and required smaller areas of ablation [7.0 (5.9-14.2) cm2 vs 11.4 (8.5-16.7) cm2, P = .06]. Both groups experienced comparable procedure times, fluoroscopy doses, ablation times, VT cycle lengths, and acute success rates. After final ablation, VA-free survival was comparable between both groups (65% vs 63%; P=.63) at 12 months. Idiopathic NICM-related VT with near-normal LVEF was associated with discrete areas of arrhythmogenic, predominantly intramural, scar in the perivalvular LV and basal septum. Despite smaller scar, patients required similar ablation amounts and experienced comparable long-term outcomes compared to patients with idiopathic NICM-related VT and impaired LVEF. These findings underscore the "three-dimensionality" of substrate, whereby the intramural basal septum forms the third dimension and impacts ablation outcomes.