Cardiomyopathies in children and adolescents: aetiology, management, and outcomes in the European Society of Cardiology EURObservational Research Programme Cardiomyopathy and Myocarditis Registry

Childhood-onset cardiomyopathies are rare and poorly characterized. This study examined the baseline characteristics and 1-year follow-up of children with cardiomyopathy in the first European Cardiomyopathy Registry.Prospective data were collected on individuals aged 1-<18 years enrolled in the European Society of Cardiology EURObservational Research Programme Cardiomyopathy and Myocarditis long-term registry (June 2014-December 2016).A total of 633 individuals aged ≤18 years with hypertrophic [HCM; n = 388 (61.3%)], dilated [DCM; n = 206 (32.5%)], restrictive [RCM; n = 28 (4.4%)], and arrhythmogenic right ventricular cardiomyopathy [ARVC; n = 11 (1.7%)] were enrolled by 23 referral centres in 14 countries. Median age at diagnosis was 4.0 [interquartile range (IQR) 0-10] years, and there was a male predominance [n = 372 (58.8%)] across all subtypes, with the exception of DCM diagnosed <10 years of age; 621 (98.1%) patients were receiving cardiac medication and 80 (12.6%) had an implantable cardioverter-defibrillator. A total of 253 patients (253/535, 47.3%) had familial disease. Genetic testing was performed in 414 (67.8%) patients with a pathogenic or likely pathogenic variant reported in 250 (60.4%). Rare disease phenocopies were reported in 177 patients (28.0%) and were most frequent in patients under 10 years [142 (30.9%) vs. 35 (19.6%); P = .003]. Over a median follow-up of 12.5 months (IQR 11.3-15.3 months), 18 patients (3.3%) died [HCM n = 9 (2.6%), DCM n = 5 (3.0%), RCM n = 4 (16.0%)]. Heart failure events were most frequent in RCM patients (36.0%).The findings confirm the heterogeneous aetiology of childhood cardiomyopathies and show a high frequency of familial disease. Outcomes differed by cardiomyopathy subtype, highlighting a need for disease-specific evaluation and treatment.