BACKGROUND: We assessed the influence of interventricular septal thickness (IVSd) on the clinical outcome and survival after alcohol septal ablation (ASA) in patient with hypertrophic cardiomyopathy.

METHODS AND RESULTS: We analyzed 531 patients with hypertrophic cardiomyopathy (age: 56±14 years, men 55%) treated with ASA. Survival status was obtained 7.9±4.0 years after ASA. Baseline IVSd was inversely associated with survival (hazard ratio [HR] for 1 mm increment, 1.13; confidence interval, 1.05-1.21; P<0.001) after adjustment for age, sex, body mass index, and ASA-performing center. Compared with patients with baseline IVSd <20 mm, patients with baseline IVSd ≥25 mm had reduced survival (HR, 5.0; CI, 2.1-12), whereas patients with baseline IVSd 20 to 24 mm had similar survival (HR, 1.4; CI, 0.7-2.8). Baseline IVSd was not correlated with New York Heart Association class, Canadian Cardiology Society class, or syncope. Clinical outcome was assessed 0.6±0.6 years after ASA. IVSd was not related to left ventricular outflow tract gradient reduction at rest (P=0.883) or during Valsalva maneuver (P=0.885). The proportion of patients in New York Heart Association class 3 to 4 was reduced from 86% to 10%; in Canadian Cardiology Society class 3 to 4 from 26% to 2%; and with syncope from 25% to 2%. There were no correlations between baseline IVSd and New York Heart Association class (P=0.067), Canadian Cardiology Society class (P=0.106), or syncope (P=0.426) after ASA.

CONCLUSIONS: ASA had equal effects on left ventricular outflow tract gradients and symptoms throughout the spectrum of septal hypertrophy. Severe septal hypertrophy before ASA remained a marker of reduced survival after ASA with a 5-fold increased risk of all-cause mortality in patients with baseline IVSd >25 mm compared with patients with baseline IVSd <20 mm.