Sudden Cardiac Death and its Relation to Previously Diagnosed or Occult Cardiac Disease at Autopsy

BACKGROUND: Sudden cardiac death (SCD) prevention focuses on individuals with diagnosed disease (ie, conventional SCD risk factors RFs) such as reduced ejection fraction and myocardial infarction (MI). The burden of occult disease among community SCDs without diagnosed RFs is unknown and represents a target for prevention through increased detection. OBJECTIVES: This study sought to determine the sensitivity of diagnosed RFs for community sudden deaths and identify cardiac pathology, including occult MI and dilated cardiomyopathy (DCM), among community sudden deaths without diagnosed RFs. METHODS: The POST SCD (POstmortem Systematic invesTigation of Sudden Cardiac Death) is a prospective countywide study using autopsy to adjudicate arrhythmic (potentially rescuable with defibrillator) or nonarrhythmic (eg, tamponade, overdose) deaths among presumed SCDs meeting World Health Organization criteria. We assessed prevalence ("sensitivity") of diagnosed RFs (ejection fraction ≤35%, heart failure, prior MI, syncope) among arrhythmic, nonarrhythmic, and reference trauma deaths. Among arrhythmic deaths without diagnosed RFs, we assessed occult cardiac pathologies including DCM (short-axis diameter ≥3.5 cm and heart weight 1 SD more than expected based on sex, age, height, and weight; Z-score =1) and healed MI (histopathological evidence of healed MI). RESULTS: Of 877 presumed SCDs, 513 (58%) were autopsy-defined arrhythmic deaths, of which 166 subjects (32%) had diagnosed RFs (mean age: 64.3 years; 77% men); therefore, sensitivity of RFs for arrhythmic death was 32%. Another 159 subjects (31%) had occult MI or DCM with similar demographics (mean age: 62.6 years; 80% men) and cardiac pathologies as those with RFs, including fibrosis and coronary disease. The remaining 185 arrhythmic deaths (36%) were subjects who were younger (mean age: 56.9 years) with less cardiac pathology than arrhythmic deaths with occult MI or DCM but still had increased heart weight (Z-score: 0.9 vs 0.0), larger left ventricular diameter (2.5 cm vs 1.9 cm), and more significant coronary disease (52% vs 13%, all P < 0.001) but similar fibrosis (6.7% vs 6.3%) and left ventricular hypertrophy burden (57% vs 55%) than trauma deaths. CONCLUSIONS: In this 12-year countywide postmortem study, two-thirds of community arrhythmic SCDs occurred in individuals without diagnosed disease despite substantial cardiac pathology; half of these "silent" arrhythmic deaths had occult MI or DCM. Improved detection of occult cardiac disease is a critical priority to reduce community sudden deaths.