Introduction: Heart failure (HF) and left ventricular ejection fraction (EF) assessment have been hallmarks of sudden cardiac death (SCD) risk stratification for over 20 years. However, their sensitivity, specificity, and positive predictive value (PPV) for true arrhythmic death in the general population are unknown because nearly all SCD studies presume arhythmic causes. Aims: To define sensitivity, specificity, and PPV of current SCD risk stratification criteria for the autopsy-confirmed arrhythmic cause among countywide sudden deaths. Methods: POST SCD (POstmortem SysTematic Investigation of Sudden Cardiac Death) is a prospective cohort study using autopsy, clinical records, and toxicology to adjudicate arrhythmic (SAD; potentially rescuable with implantable defibrillator) or non-arrhythmic (non-SAD; e.g., tamponade, overdose) causes among presumed SCDs (pSCDs) in San Francisco County. We analyzed sensitivity, specificity, and PPV for syncope, EF≤35%, diagnosed HF, or the presence of any of 3 factors to discriminate SADs among pSCDs. Results: Between February 2011 and September 2022, 845 of 904 (93%) pSCDs 18-90 years had complete medical records available, of which 491 (58%) were SADs. Seventy-three pSCDs had history of syncope, with similar prevalence in SADs and non-SADs (p=0.4), while prevalence of HF was higher in SADs vs. non-SADs (88/491[18%] vs. 39/354 [11%], p=0.003). EF assessment was performed in 206 pSCDs (24%, 133 SADs, 73 non-SADs); prevalence of EF ≤ 35% was similar between SADs and non-SADs (p=0.112). A greater proportion of SADs had ≥1 factor than non-SADs (122/491[25%] vs. 65/354 [18%], p=0.015). Sensitivity of syncope, EF≤35%, HF, ≥1 factor for SAD was 9, 26, 17, 25%, specificity was 92, 82, 90, 82%, and PPV was 60, 73, 69, 65%, respectively. Conversely, 369 of 491 (75%) SADs had no risk factors before sudden death. Defibrillators were implanted in 4/491 (0.8%) SADs. Conclusions: In this 11-year countywide postmortem study, conventional risk factors had low sensitivity and PPV but high specificity for autopsy-confirmed arrhythmic cause of sudden death. Three-fourths of SADs had no risk factors before sudden death, highlighting the need for improved risk prediction in the general population.
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