BACKGROUND: Congenital heart defects (CHD) are among the leading causes of sudden cardiac death (SCD) in the young. Nationwide incidence of SCD in people with CHD (SCD-CHD) has not been established in the young general population. The aims of this study were to investigate incidence of SCD-CHD and whether incidence of SCD-CHD in infants declined after implementation of nationwide fetal ultrasound screening in Denmark.

METHODS: All deaths (n=11 451) among people aged 0 to 35 years in Denmark in 2000 to 2009 (24.4 million person-years) were included. Danish death certificates, autopsy reports, records from hospitals and general practitioners, and data from nationwide Danish registries were used to identify SCD-CHD cases.

RESULTS: We identified 90 (11%) cases of SCD-CHD from 809 SCD. The incidence rate of SCD-CHD was 0.4 per 100 000 person-years among people aged 0 to 35 years. In total, 53 (59%) were diagnosed with CHD before death. Incidence of SCD was 9.6× higher among patients with CHD compared with people without CHD ( P<0.01). Annual incidence of physical activity-related SCD-CHD among patients aged 2 to 35 years diagnosed with CHD was 0.9 per 100 000. The annual incidence rate of SCD-CHD in infants declined after implementation of nationwide fetal ultrasound screening (incidence rate ratio, 3.8; P<0.01).

CONCLUSIONS: The proportion of SCD-CHD in the young was 11%, which is higher than previously reported. Physical activity-related SCD-CHD was a rare event among patients with CHD. We observed an ≈4-fold lower incidence of SCD-CHD among infants born after implementation of nationwide screening.