Cardiac Deceleration Capacity Refines Sudden Cardiac Death Risk Stratification in Patients with Hypertrophic Cardiomyopathy for Primary Prevention

BACKGROUND: Precise sudden cardiac death risk stratification in hypertrophic cardiomyopathy remains challenging. Parasympathetic dysfunction is closely related to malignant ventricular arrhythmias, and deceleration capacity is a robust parameter to quantify vagal tone. This study aims to elucidate the association between deceleration capacity and sudden cardiac death risk in hypertrophic cardiomyopathy. METHODS: A total of 648 hypertrophic cardiomyopathy patients completing 24-hour ambulatory Holter monitoring were consecutively enrolled in this cohort study. Baseline deceleration capacity was calculated from the Holter recordings. The primary endpoint was a composite of sudden cardiac death or sudden-cardiac-death-equivalent events including sudden death, resuscitated cardiac arrest, and appropriate implantable cardioverter-defibrillator (ICD) therapies. RESULTS: There were 464 patients included in final analysis. During mean follow-up of 827 days, 33 (7.1%) patients met primary composite endpoint. Deceleration capacity showed a significant linear inverse association with this composite endpoint (hazard ratio 0.660 [95% confidence interval, 0.546-0.799], P < 0.001). The derived cut-off value was 6.25 ms. Adding deceleration capacity to the traditional risk model significantly improved risk discrimination (C-statistic increased from 0.732 to 0.827, Delong P = 0.019) especially in the intermediate-risk subgroup (C-statistic increased from 0.565 to 0.849, Delong P = 0.011). Patients with lower deceleration capacity and elevated risk score suffered the worst outcome (Log-rank P < 0.001). CONCLUSIONS: Deceleration capacity independently predicts sudden cardiac death risk in hypertrophic cardiomyopathy and provides significant prognostic value particularly in the clinically challenging intermediate-risk subgroup. Integration of deceleration capacity into risk evaluation warrants prospective validation before guiding ICD decision-making.