Real-world clinical burden of obstructive hypertrophic cardiomyopathy: a nationwide study in france

Background Obstructive hypertrophic cardiomyopathy (oHCM) is associated with excess mortality and frequent cardiovascular (CV) events. Real-world evidence is limited and existing published estimates may differ according to cohort definition, severity mix, and follow-up duration. Purpose The objective of the study was to describe the recent clinical burden of oHCM in France on a long-term follow-up using a representative claims-based sample. Methods This retrospective cohort study used the ESND, a 2% representative sample of the French National Health Data System (SNDS). Adults (≥18 years) with an incident hospital stay for oHCM between 2014–2023 were included and followed until 2024. Patients were included if assigned to oHCM (ICD-10 code I42.1) as principal diagnosis, or to other cardiomyopathies (I42.2, I42.9) when associated to septal reduction therapy or pacemaker implantation. Patients captured only via associated diagnosis were not included. Patients with confounding diseases (aortic stenosis, hypertensive heart disease, storage disease, amyloidosis) were excluded across the full study period. Baseline NYHA class was assigned with a clustering algorithm based on treatments and symptoms. Outcomes were all-cause death, major cardiovascular (CV) events (MACE) including stroke, myocardial infarction (MI) and CV death, admission for CV reason or any cause, reported as annual incidence rates per patient-year (PY) and yearly probability from time-to-event analyses. Results Among 655 HCM patients identified, 178 oHCM patients met eligibility, equivalent to 8,900 patients after extrapolation at a national level; 44% were classified as NYHA I/II and 56% as NYHA III/IV. Mean age at baseline was 60.7+15.5 years (54.1 if NYHA I/II vs 65.9 if NYHA III/IV); 56% were male. Average follow-up was 5.7+5.2 years (6.6 if NYHA I/II vs 4.9 if NYHA III/IV) during which 46 patients (26%) died (17% if NYHA I/II vs 33% if NYHA III/IV). Estimated probability of death was 3.7% 6.5% and 9.7% at 1, 2 and 5 years, respectively for NYHA I/II and 4.0%, 9.2% and 23.7% for NYHA III/IV, respectively. Annual all-cause mortality incidence was 2.5 vs 6.7 per 100 PY in NYHA I/II vs III/IV. The incidence of MACE (2,497 vs 4,528 per 100,000 PY for NYHA I/II vs III/IV), admission for CV reasons (24,970 vs 44,659 per 100,000 PY for NYHA I/II vs III/IV), and admission of any cause (100,265 vs 169,786 per 100,000 PY for NYHA I/II vs III/IV) increased with NYHA classes. Conclusion oHCM was associated with substantial mortality and high rates of CV admissions and MACE, with marked gradients by NYHA severity. Mortality estimates aligned with existing studies, while most non-fatal event incidences were lower, likely reflecting younger cohort and longer follow-up. These results refine contemporary real-world evidence for oHCM outcomes.