Undiagnosed Heart Disease Account for a Large Share of Sudden Cardiac Deaths

While myocardial infarction (MI) accounts for a substantial proportion of sudden cardiac deaths (SCDs), most arrhythmic SCDs occur in individuals without previously diagnosed risk factors, often due to occult cardiac disease such as silent MI or dilated cardiomyopathy. In the 12-year US countywide POST SCD autopsy study, 943 presumed sudden deaths were evaluated, with 62% confirmed as cardiac; among these, 41% were attributable to MI, including both obstructive coronary artery disease (90%) and myocardial infarction with nonobstructive coronary arteries (MINOCA, 10%), with notable racial differences. The left anterior descending and right coronary arteries were most frequently involved, and nonarrhythmic mechanisms were more common in MINOCA-related deaths. In parallel analyses of 877 cases, only 32% of arrhythmic SCDs had known clinical risk factors such as reduced ejection fraction or prior MI, indicating low sensitivity of traditional risk stratification. Importantly, among those without known risk factors, nearly one-third had occult MI or dilated cardiomyopathy with similar pathological features to diagnosed cases, while the remainder—often younger individuals—still exhibited subclinical structural abnormalities, including increased heart size and coronary disease. These findings highlight that a large proportion of SCDs arise from undetected cardiac pathology and underscore the urgent need for improved screening and early detection strategies to prevent sudden death in the community. Source: https://www.jacc.org/