Myocardial Extracellular Volume Is Not Associated With Malignant Ventricular Arrhythmias in High-risk Hypertrophic Cardiomyopathy.

INTRODUCTION AND OBJECTIVES: Myocardial interstitial fibrosis, a hallmark of hypertrophic cardiomyopathy (HCM), has been proposed as an arrhythmic substrate. Fibrosis is associated with increased extracellular volume (ECV), which can be quantified by computed tomography (CT). We aimed to analyze the association between CT-determined ECV and malignant ventricular arrhythmias.

METHODS: A retrospective case-control observational study was conducted in HCM patients with implantable cardioverter-defibrillator, undergoing a CT-protocol with continuous iodine contrast infusion to determine equilibrium ECV. Left ventricular septal and lateral CT-determined ECV was compared between prespecified cases (malignant arrhythmia any time before CT scan) and controls (no prior malignant arrhythmias) and among ECV tertiles.

RESULTS: A total of 78 implantable cardioverter-defibrillator HCM patients were included; 24 were women, with a mean age of 52.1 ± 15.6 years. Mean ECV ± standard deviation in the septal left ventricular wall and was 29.8% ± 6.3% in cases (n = 24) vs 31.9% ± 8.5% in controls (n = 54); P = .282. Mean ECV in the lateral wall was 24.5% ± 6.8% in cases vs 28.2% ± 7.4% in controls; P = .043. On comparison of the entire population according to septal ECV tertiles, no significant differences were found in the number of patients receiving appropriate shocks. Conversely, we found a trend (P = .056) for a higher number of patients receiving appropriate shocks in the lateral ECV lowest tertile.

CONCLUSIONS: Extracellular volume was not increased in implantable cardioverter-defibrillator HCM patients with malignant ventricular arrhythmias vs those without arrhythmias. Our findings do not support the use of ECV (a surrogate of diffuse fibrosis) as a predictor of arrhythmias in high-risk HCM patients.