Epidemiology and prognosis of obstructive and non-obstructive hypertrophic cardiomyopathy in Finland: a nationwide cohort study

Abstract Background Hypertrophic cardiomyopathy (HCM) is an often hereditary myocardial disease. The Finnish population has a specific genetic background, which may influence and even predispose people to various hereditary diseases. Whilst advances in genetic testing and imaging techniques may have influenced the detection of HCM and associated subtypes, contemporary data on incidence and prevalence remain limited. Purpose This study aimed to evaluate the current trends in the incidence, prevalence, and prognosis of obstructive and non-obstructive HCM in a nationwide cohort in Finland. Methods A population-based registry study was conducted using data from Finnish nationwide healthcare registries (HILMO/avoHILMO) including individuals aged at least 12 years with recorded HCM diagnosis between 2000 and 2021. The incidence was calculated by dividing the number of newly diagnosed HCM patients by the Finnish background population. Furthermore, the mean incidence per age-group was calculated by dividing the sum of age-group specific incidences by the number of age groups. The date and cause of death were obtained from national registries (Statistics Finland). Mortality was computed by dividing the number of deaths by follow-up length. Patients were followed from 2014 to 2021, and incident cases were defined as new diagnoses after 2014. HCM cases were stratified into obstructive HCM and non-obstructive HCM based on ICD-10 codes I42.1 and I42.2, respectively. Results Among 5,834 documented patients with HCM, the overall mean incidence by age-group was 2.64/100,000, with incidence increasing with age, peaking in those aged ≥85 years (6.22/100,000 patient-years [PY]). Annual incidence of obstructive HCM decreased from 2.2 to 1.4/100,000 PY, while non-obstructive HCM increased from 4.6 to 5.4/100,000 PY between 2014 and 2021 (Fig 1). Prevalence of non-obstructive HCM rose from 40 to 56/100,000 PY, while obstructive HCM prevalence remained stable (23-24/100,000 PY). All-cause mortality was 5.5/100 PY, with obstructive and non-obstructive HCM mortality at 5.7 and 4.6/100 PY, respectively. HCM-specific deaths accounted for 16% and 12% of all deaths in patients with non-obstructive and obstructive HCM, respectively. Conclusions This nationwide study in Finland revealed an increasing incidence and prevalence of non-obstructive HCM over time, contrasting with stable rates among patients with obstructive HCM. Incidence and prevalence were strongly age dependent. Non-HCM-related deaths were predominant in both HCM subtypes.