Heart failure (HF) in children is a severe condition which diagnosis can be difficult. Time from first symptoms to diagnosis, called time to diagnosis (TTD) is related to prognosis in several diseases.

The aim of this study was to measure TTD in children with new-onset HF and assess its consequences and determinants. The pediatric incidence of new-onset HF was determined.

A retrospective population-based observational study was conducted between 2007 and 2016 in a French tertiary care center. All children under 16 years old with no known heart disease and new-onset HF confirmed by echocardiography were included. Two junior doctors assessed TTD independently. With logistic regression used for outcomes and a Cox proportional-hazards model for determinants, analyses were stratified by HF etiology: congenital heart diseases (CHD) and cardiomyopathies/myocarditis (CM).

A total of 117 children were included (median age [interquartile range (IQR)] 25 days (6–146), 50.4% were male, 60 had CHD and 57 had CM). The incidence of new-onset HF in children was 2.07 per 100,000 including 0.98 per 100 000 due to CM. Overall median (IQR) TTD was 3.3 days (1.0–21.2); it was 2.2 days (0.6–16.5) with CHD and 5.0 days (2.0–28.1) with CM. The frequency of 1-year mortality was 17% and 1-year neuromotor sequel 18%. Death at 1 year was associated with low birth weight for all children (adjusted odds ratio 0.24, 95% confidence interval [CI] 0.08–0.68) and TTD below the median with CM (0.09, 0.01–0.87). Short TTD was associated with clinical severity on the first day of symptoms for all children (adjusted hazard ratio 3.39, 95% CI 2.01–5.72), and young age with CM (0.09, 0.02–0.41).

In children with new-onset HF presenting in our region, median TTD was short. Poor outcome was not associated with long TTD but with low birth weight. Our study was the first to report the pediatric incidence of new-onset HF in a French area.