Paradigm of Sudden Death Prevention in Hypertrophic Cardiomyopathy

Abstract

Hypertrophic cardiomyopathy (HCM) is a worldwide genetic heart disease and a common cause of sudden death in the young. Penetration of the implantable cardioverter-defibrillator (ICD) into this patient population over the past 20 years has made accurate selection of patients for primary prevention ICDs a priority. Consequently, a new paradigm has emerged in the management of this complex disease with ICD therapy responsible for a substantial decrease in overall HCM-related mortality (to 0.5%/y) and independent of patient age. Selection of candidates for ICDs has matured substantially with the formulation of an enhanced risk stratification algorithm. One or more contemporary risk markers judged major within a given patient’s clinical profile, in association with physician judgment and shared decision-making, is sufficient to consider a primary prevention ICD implant. An enhanced American College of Cardiology/American Heart Association risk factor model (including new contrast-magnetic resonance–based markers, such as left ventricular apical aneurysm) used prospectively to make ICD decisions proved to be 95% sensitive for identifying patients who would experience ≥1 appropriate device therapies terminating ventricular tachycardia/fibrillation. The number of HCM patients required to treat with ICDs to save 1 patient with abolition of lethal ventricular tachyarrhythmias was 6:1, similar to randomized defibrillator trials in other cardiomyopathies. In contrast to patients with ischemic heart disease, after ICD shock HCM patients rarely experience transformation to heart failure deterioration or sudden arrhythmic death. The mathematically derived risk score model proposed by the European Society of Cardiology was inferior for identifying high-risk patients susceptible to arrhythmic sudden death with a sensitivity of only 33%, leaving many patients exposed to the possibility of sudden death without ICDs. In conclusion, introduction of the ICD associated with a matured risk stratification algorithm has altered management strategy and clinical course of many HCM patients, making the likelihood of sudden death prevention a reality and fulfilling the aspiration of preservation of life and reduced mortality for this vulnerable patient population.