Nazer B, Dale Z, Carrassa G, et al. - In this study performed in contemporary hypertrophic cardiomyopathy (HCM) subcutaneous implantable cardioverter defibrillators (S-ICD) cohort, researchers evaluated the incidence as well as the predictors of appropriate and inappropriate shock (IAS). Data were obtained from HCM patients who had S-ICD implantation at 4 centers. Etiologies of all S-ICD shocks were adjudicated. The mean follow-up was 2.7 years. There were 88 HCM patients who received S-ICD (81 for primary and 7 for secondary prevention). Taller 12-lead ECG R wave amplitude and abnormal T wave inversions were identified as independent predictors of IAS. Sudden death or untreated sustained ventricular arrhythmias did not occur in any patient. Findings of this multi-center HCM S-ICD study revealed a rare occurrence of IAS and confinement of appropriate shocks to secondary prevention patients. An increased IAS risk was conferred by R wave amplitude, and T wave inversions were identified as protective. In this cohort, over-estimation of the risk of appropriate shocks by HCM primary prevention ICD guidelines was revealed.