Lower Calculated Risk for Sudden Cardiac Death in Patients with Apical Versus Non-Obstructive Non-Apical Hypertrophic Cardiomyopathy

Background: It remains controversial whether non-obstructive apical hypertrophic cardiomyopathy (apical HCM) is associated with a lower risk for sudden cardiac death (SCD) compared to patients with non-obstructive, non-apical HCM (NONA HCM).

Methods: Single center retrospective study of a hypertrophic cardiomyopathy (HCM) cohort in a tertiary center clinic. The 5-year SCD risk was calculated based on the HCM risk-SCD tool.

Results: A total of 109 patients included in the cohort (65 patients with NONA HCM and 44 patients with apical HCM) were pre-dominantly male at a mean age of 55 years and mean age at diagnosis of HCM of 41 years. Patients with apical HCM had a significant lower calculated 5-year risk for SCD compared to patients with NONA HCM (2.65±2.2% versus 4.00±3.5%, respectively, p=0.017), primarily due to a lower incidence of familial SCD (20% versus 43% respectively, p=0.014). Only 9% of patients with apical HCM had a calculated risk of >6% (high risk, implantable cardioverter defibrillator recommended), as compared to 23% of patients with NONA HCM. During a median follow-up of 1,001 days, apical HCM patients tended to develop less malignant ventricular arrhythmia episodes compared to NONA HCM patients (0% versus 7.7%, respectively, p=0.060).

Conclusion: Apical HCM patients have a lower calculated risk of SCD compared to NONA HCM patients based on the HCM risk-SCD score, mainly due to a lower incidence of family history of SCD. Thus, apical HCM should be considered a form of HCM less prone to SCD.