Sudden Cardiac Death Risk over Time in HCM Patients with Implantable Cardioverter-Defibrillator.

Background: In patients with HCM at high risk of SCD, an ICD should be considered as a standard of care. Current risk approximation algorithms recommended by ESC 2014 criteria indicate that SCD risk is not stable. The aim of the study was to investigate how the calculated SCD risk in HCM patients with an ICD implanted in the past changed over time. Methods: We analyzed 64 HCM patients with ICD for primary prevention, referred for ICD re-implantation, and 32 HCM patients referred for a first-time ICD placement during the same period. The 5-year-SCD risk was assessed for suitable patients using the recommended ESC calculator. Results: The first-time group had a higher 5-year-SCD risk than those referred for ICD re-implantation: 7.50 (IQR 5.98−10.46) vs. 4.88 (IQR 3.42−7.25), p < 0.05. Out of the patients with an initial calculated risk below 4%, the risk increased in 22% of cases, reaching the 4−6% range. In 78% of patients, the risk remained stable and low. In 31% of patients with an initial calculated SCD risk ≥ 6%, the risk decreased over time to below 6%, and in 14% of the cases, below 4%. Conclusions: SCD risk in HCM patients is usually stable or gets lower. Our data suggest it is important to re-evaluate the risk profile for patients with HCM when ICD re-implantation is considered.