Validation of Guideline Recommendation on Sudden Cardiac Death Prevention in Hypertrophic Cardiomyopathy

Background: To prevent sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HCM), the HCM Risk-SCD calculator and guideline recommendations are used to aid decision making for implantable cardioverter-defibrillator placement. Objectives: The aim of this study was to assess the clinical profiles and occurrence of SCD by phenotypes of HCM and validate the performance of the current guidelines from a large-scale Japanese multicenter registry. Methods: This was a retrospective, multicenter, observational, longitudinal cohort study that enrolled 3,611 consecutive patients with HCM. The primary endpoint was a composite of SCD or an equivalent event. Results: The 5-year cumulative incidence of SCD events was markedly high in patients with end-stage HCM, defined by ejection fraction <50% (18.5%), followed by midventricular obstruction and nonobstructive HCM (6.9% and 4.7%). The 5-year cumulative incidence rates of SCD events for each recommendation class by the 2 guidelines were as follows: with the 2024 ACC (American College of Cardiology)/AHA (American Heart Association) guidelines, 23.8%, 7.2%, 5.7%, and 2.3% for Classes 1, 2a, 2b, and 3, respectively, and with the 2023 ESC (European Society of Cardiology) guidelines, 23.8%, 2.9%, 9.3%, and 2.6%, respectively. The 5-year risk was not well stratified between Classes 2a and 2b with the 2024 ACC/AHA guidelines (P = 0.101), and the event rate was even reversed with the 2023 ESC guidelines (P = 0.545). Conclusions: Among HCM phenotypes, the prognosis of patients with end-stage HCM was markedly worse. The 2024 ACC/AHA and 2023 ESC guidelines well stratified SCD risk in patients with HCM; the 2024 ACC/AHA guidelines seemed to better stratify SCD risk between Classes 2a and 2b compared with the 2023 ESC guidelines.