Objectives: Sudden cardiac death (SCD) is a leading cause of mortality among individuals with congenital heart disease (CHD), and risk stratification remains challenging. This study aimed to describe the underlying structural cardiac abnormalities in a national cohort of SCD victims with CHD, their socioeconomic status, and interactions with the healthcare system before death.

Methods: The Swedish study of Sudden Cardiac Death in the Young, 2000–2010, included SCD victims under 36 years, along with population-based controls and their parents. Of 903 SCD victims, 39 with autopsy-defined CHD were included in this study, together with 195 controls. Information on socioeconomic variables and healthcare contacts was gathered from Swedish national registers.

Results: The median age for SCD was 24 years, and 64% were male. The CHD was undiagnosed before death in 31% of the cases, of whom 8 had coronary anomalies. Moderate to complex CHD was observed in 41%. Structural abnormalities of the ventricles were prevalent, with left ventricular hypertrophy present in 56% and fibrosis in 64%. The cases had a higher frequency of hospital admissions within 6 months before SCD compared to controls (OR 14.1,95% CI 3.80–52.44), p < 0.001. No socioeconomic differences were observed.

Conclusions: This study identified a broad spectrum of underlying anatomical defects, with ventricular structural abnormalities being a common autopsy finding. The majority of cases had moderate to severe lesions. An increased frequency of healthcare contacts prior to death was noted, which may be a variable needing more attention as a predictor for a higher risk of SCD.