Sudden unexpected death in persons less than 40 years of age.

This study retrospectively assesses the underlying causes of sudden unexpected death and the occurrence of prodromal symptoms in 162 subjects (aged 9 to 39 years) over a 10-year period (1976 to 1985). Underlying cardiac diseases accounted for sudden death in 73% and noncardiac causes in 15% of subjects. In 12% of subjects, the causes were unidentifiable. Myocarditis (22%), hypertrophic cardiomyopathy (22%) and conduction system abnormalities (13%) were the major causes in 32 subjects aged less than 20 years. Major causes of 46 deaths in subjects 20 to 29 years were atherosclerotic coronary artery disease (24%), myocarditis (22%) and hypertrophic cardiomyopathy (13%). The largest number of deaths in 84 subjects aged greater than or equal to 30 years was attributed to coronary artery disease (58%), followed by myocarditis (11%). Among noncardiac causes of sudden death, intracranial hemorrhage was the most frequent (5%), followed by infectious disease (4%). Prodromal symptoms were reported by 54% of subjects; most frequent were chest pain (25%) in subjects aged greater than or equal to 20 years, and dizziness (16%) in those aged less than 20. Sudden death, which occurred during routine daily activity in 49% and during sleep in 23% of subjects, was related to physical exercise in 23% and emotional upset in 6%. Sudden unexpected death in the young is still an unresolved medical problem. The early recognition of prodromal symptoms could be crucial in the prevention of sudden death, specifically when exercise-related.