A prospective countywide postmortem study (POST SCD: POstmortem Systematic invesTigation of Sudden Cardiac Death) published in the Journal of the American College of Cardiology evaluated the contribution of diagnosed risk factors (RFs) and occult cardiac disease in community sudden cardiac death (SCD). The study included 877 presumed SCD cases meeting World Health Organization criteria over a 12-year period. Autopsy adjudication classified deaths as arrhythmic or non-arrhythmic. 

Conventional RFs included reduced ejection fraction (≤35%), prior myocardial infarction (MI), heart failure (HF), and syncope. Inclusion criteria comprised presumed SCD cases undergoing systematic autopsy evaluation, while exclusion criteria were not explicitly detailed in the abstract. Among arrhythmic deaths without diagnosed RFs, occult cardiac pathologies such as dilated cardiomyopathy (DCM) and healed MI were assessed using predefined morphologic and histopathologic criteria.

Of the 877 cases, 513 (58%) were confirmed as arrhythmic deaths. Among these, only 166 individuals (32%) had known RFs, indicating limited sensitivity of conventional RFs for predicting arrhythmic SCD. Among the remaining cases without RFs, 159 individuals (31%) had occult MI or DCM, with similar demographic and pathological profiles to those with known RFs.

The remaining 185 cases (36%) were younger (mean age 56.9 years) and showed less overt pathology but demonstrated increased heart weight (Z-score 0.9 vs 0.0), larger left ventricular diameter (2.5 cm vs 1.9 cm), and higher prevalence of coronary disease (52% vs 13%; p<0.001) compared with trauma deaths, while fibrosis and left ventricular hypertrophy were comparable.

A substantial proportion of arrhythmic SCD occurred without prior diagnosed RFs. Occult structural and ischemic abnormalities were frequently identified in these cases.