Rethinking Risk in Hypertrophic Cardiomyopathy: Assessing the Role of Myocardial Fibrosis and Left Ventricular Hypertrophy in Sudden Cardiac Death

The American College of Cardiology/American Heart Association guidelines recommend implantable cardioverter-defibrillator (ICD) implantation for patients with hypertrophic cardiomyopathy (HCM) with a wall thickness of ≥30 mm (class IIA), whereas they give a class IIB recommendation for the implantation of an ICD on the basis of extensive late gadolinium enhancement alone. In this analysis, we show that in a high-risk population with ICD implanted for primary prevention of sudden cardiac death (SCD) in the setting of HCM, the presence of massive left ventricular hypertrophy predicts a higher incidence of ICD therapy than other traditional SCD risk factors. The presence of extensive myocardial fibrosis, however, identifies a subgroup of patients without massive left ventricular hypertrophy who have an equally high incidence of receiving appropriate device therapy. These findings suggest that the presence of extensive late gadolinium enhancement on cardiac magnetic resonance can be used as a risk modifier for traditional SCD risk factors in patients with HCM to better understand their overall risk of ventricular arrhythmias.