Hypertrophic cardiomyopathy (HCM) is considered to be the first cause of sudden death in young subjects, including competitive athletes, often in the absence of significant symptoms. However, most of these data come from tertiary centers and the clinical profile of these patients, as well as their management in real life in France, remain poorly understood.

To evaluate the management of young adults with sarcomeric HCM and the predictive factors for major cardiac event (MCE), patients <25 years included in the national HCM register “REMY” of the French Society of Cardiology from 2006 to 2018 were identified.

At inclusion was calculated the European 5-year sudden cardiac death (SCD) score and identified the presence of the 5 major classical SCD risk factors (MRF). At follow-up, MCE [SCD or implantable cardioverter defibrillator (ICD) shock, sustained ventricular tachycardia (SVT), atrial fibrillation (AF), stroke, hospitalization for heart failure (HFH) or syncope] were notified.

Among 61 included patients [20.5±3(16–25) years, 16(26%) women], 92% were in NHYA class I/II, 18(30%) obstructive, 37(86%) showed MRI fibrosis, 6(12%) abnormal exercise blood pressure response, 25% a family history of SCD, 13(21%) had a prophylactic ICD. The score (4.8±3.2%) was <4% in 53% and ≥6% in 25% of patients. After 4.4±2.2years, 15(25%) patients (7 women) presented 18 MCE: 3 SCD (17%), 5 SVT (28%), 5 AF and 1 stroke (33%), 1 HFH (5%), 3 unexplained syncopal episodes (17%); 10 patients received an ICD (4 in secondary prevention). 61% patients with score>6% had an ICD. Female sex was predictive of MCE (P=.02), with a tendency for obstruction (P=.09), but not late gadolinium enhancement, prophylactic ICD or MRF.

Thus, in young adults with HCM, MCE are common, especially in women, more often rhythmic. Prophylactic ICD is frequent, especially if the score exceeds 6%, but MCE are difficult to predict using the current criteria.