Introduction: Clonal hematopoiesis of indeterminate potential (CHIP) has been associated with an increased risk of coronary artery disease (CAD) and cardiovascular (CV) mortality. Whether CHIP may affect myocardium beyond promoting CAD, or its potential association with sudden cardiac death (SCD), the most feared manifestation of CV disease, is unknown. Research Questions/Hypothesis: We hypothesize that CHIP-mutant macrophages infiltrate the myocardium and are associated with autopsy-defined arrhythmic death. Goals/Aims: (1) determine rate of CHIP at time of death in an unselected, countywide study of all incident sudden deaths; (2) evaluate whether CHIP-mutant macrophages infiltrate into myocardium; and (3) evaluate potential association of CHIP with autopsy-confirmed arrhythmic causes among countywide sudden deaths Methods/Approach: We used autopsy to adjudicate arrhythmic from non-arrhythmic (PE, stroke, overdose, tamponade) causes in 1,148 sudden deaths and 141 trauma control deaths in San Francisco County from 2011-23. DNA was extracted from frozen blood samples collected at time of death from 399 consented cases. Sequencing of 22 CHIP-associated genes was performed to ~2000x mean target coverage. All pathogenic/likely pathogenic CHIP variants at >2% variant allele frequency (VAF) were considered CHIP+. DNA was then isolated from left ventricular (LV) tissue sampled at autopsy in all CHIP+ blood cases and sequenced as above. Results: Of 399 consented cases, 70 blood samples (17.5%) were CHIP+ (range 2%-39.6%; mean age 70.6 years vs. 58.1 years for CHIP-). The most frequent mutant genes were DNMT3A, TET2, and ASXL1. Proportion of arrhythmic causes among sudden deaths was similar for CHIP+ vs. CHIP- cases (36 of 70 [52%] vs. 171 of 329 [51%]). Sequencing of available LV tissue from 61 CHIP+ blood cases revealed 67% (n=41) harbored the same CHIP mutation identified in blood at >0.2% VAF (range 0.2%-4.3%). Proportion of arrhythmic causes among sudden deaths was significantly higher in cases where both blood and LV were CHIP+ (24 of 41 [58.5%] vs. 5 of 19 [26.3%] CHIP+ blood/CHIP- LV, p=0.02). Conclusions: Prevalence of CHIP positivity at sudden death is similar to published studies and correlated with age. CHIP+ status in myocardial tissue but not peripheral blood was associated with arrhythmic causes of sudden death, suggesting a direct tissue effect of CHIP-mutant macrophages.

BACKGROUND:Sudden cardiac death (SCD) genetic studies neglect the majority occurring in older decedents with cardiovascular pathology. OBJECTIVES:This study sought to determine the burden of genetic disease in unselected adult sudden deaths by precision genotype-postmortem phenotype correlation. METHODS:The authors used autopsy, histology, and toxicology to adjudicate cause and identify high-suspicion phenotypes (eg, hypertrophic cardiomyopathy) among presumed SCDs aged 18 to 90 years referred to the county medical examiner from February 2011 to January 2018. They tested 231 genes associated with sudden death and correlated genotype with postmortem phenotypes, including myocardial analysis. Family history in high-suspicion phenotype cases was obtained. RESULTS:Of 856 autopsied presumed SCDs, families of 359 consented and 306 cases (66% cardiac cause) ultimately underwent genetic testing (mean age 62 years, 74% male). Seventy-five cases met high-suspicion phenotype criteria (8.8%), of which 36 underwent testing; 18 families met with a genetic counselor. We found 14 cases with autosomal dominant or X-linked pathogenic/likely pathogenic (P/LP) variants (apparent yield 4.6%); 6 had concordant cause (corrected yield 2%). Yields restricted to autopsy-confirmed cardiac causes (2.5%) and high-suspicion phenotypes (2.7%) were similar. Myocardial genotyping in 14 high-suspicion decedents matched negative blood genotyping, thus did not support somatic mosaicism. Myocardial RNA in a P/LP PKP2 carrier without phenotype demonstrated nonsense-mediated escape as potential mechanism for incomplete penetrance. One-half of high-suspicion cases had a family history of a related condition or sudden death. CONCLUSIONS:In this 7-year countywide study, 2% of total sudden deaths and 2.5% of confirmed SCDs had identifiable genetic cause, corrected for genotype-phenotype concordance. These results do not support routine genetic testing for community sudden deaths, particularly without autopsy.

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.

Background: Annual incidence of sudden cardiac death (SCD) is reported at 1% in cohorts with known hypertrophic cardiomyopathy (HCM), but these estimates presume arrhythmic cause and miss occult cases dying before diagnosis. Hypothesis: Prospective surveillance and postmortem investigation of community sudden deaths will uncover the true burden of presumed SCD (pSCD) and arrhythmic death (SAD) attributable to HCM. Objectives: Determine characteristics and precise contribution of HCM to population pSCD and SAD. Methods: POST SCD (POstmortem SysTematic Investigation of Sudden Cardiac Death) is a prospective cohort study using autopsy, clinical records, and toxicology to adjudicate arrhythmic (potentially rescuable with implantable defibrillator) or non-arrhythmic (e.g., tamponade, overdose) causes among pSCDs 0-90 years in San Francisco County. We included all incident cases from 2/1/11-3/1/14 (n=525) and approximately every 3rd day from 3/1/14-9/1/22 (n=497). We identified HCM victims via 3 parallel approaches: 1) pathology criteria; 2) echocardiogram (TTE) review; 3) genetic analysis. Results: Of 1022 pSCDs in the 11-year study period, we identified 13 cases with HCM, yielding a 2% contribution to arrhythmic death burden: 10 met pathology criteria; 2 via review of 203 TTEs (missed on initial report); 1 with pathogenic ALPK3 mutation. Only 2 of 13 (15%) pSCDs with HCM had premortem diagnosis. A greater proportion of pSCDs with HCM had autopsy-confirmed arrhythmic cause than pSCDs without HCM (11/13 [85%] vs. 547/1009 [54%], p=0.03). HCM contribution to pSCD burden decreased with age (p=0.003), highest among victims <35 years, accounting for 7.1% (6/84) of pSCDs and 9.4% (3/32) of SADs. Genetic testing of 317 consented pSCDs (5/12 meeting pathologic or TTE HCM criteria) yielded pathogenic mutations in 40% (2/5), and identified 1 additional case without clinical phenotype. Conclusions: In this 11-year countywide postmortem study, HCM meeting pathologic, clinical, or genetic criteria was associated with autopsy-confirmed arrhythmic cause of sudden death, accounting for 2% of SADs, highest in cases <35 years. As 85% of cases were undiagnosed before pSCD, the true burden of HCM-related sudden death may be substantially underestimated.

Background: Titin, encoded by TTN , is a sarcomeric protein necessary for normal cardiac and skeletal muscle function. Truncating variants in the A-band are a frequent cause of isolated and familial dilated cardiomyopathy (DCM) in living cohorts. Whether variants outside of the A-band confer arrhythmic risk remains unclear. We investigated the yield and distribution of TTN variants in a postmortem study of presumed sudden cardiac deaths (pSCDs) in San Francisco County. Methods: From 2/1/2011 to 12/31/2017, the Postmortem Systematic Investigation of Sudden Cardiac Death study performed complete autopsies on 889 incident deaths (age 16-90) meeting World Health Organization criteria for SCD (pSCD). Using clinical records, autopsy findings, and family history, we performed deep phenotyping to adjudicate underlying arrhythmic “SAD” (potentially rescuable with defibrillation) or non-arrhythmic “non-SAD” (tamponade, overdose, etc.) cause of pSCD. We performed clinical whole exome testing on cases with next of kin consent. Results: Of the 322 pSCDs tested (196 SAD, 126 non-SAD), we detected 5 truncating/splice variants located in non-A-band regions (p=0.03 vs. none found in the A-band) in 4 cases, all SAD. No truncating/splice variants were detected in 47 cases with autopsy evidence of DCM (cardiomegaly and short axis > 3.5cm). Overall, 89 cases had at least 1 TTN variant of uncertain significance (VUS): 61 (68.5%) SADs and 28 (31.5%) non-SADs, with a trend towards more TTN VUSs among SADs (p =0.10). A total of 110 VUSs were found: 10 (9.1%) in the Z-disc, 38 (34.5%) in the I-band, 50 (45.5%) in the A-band, and 12 (10.9%) in the M-band. TTN VUSs clustered similarly throughout the gene in SADs and non-SADs. Conclusion: In this 7-year postmortem genetic study of unselected countywide sudden deaths using autopsy to adjudicate arrhythmic cause, we found TTN truncating/splice variants in non-A-band regions were associated with SAD and a trend toward association with SAD among TTN VUS carriers. In contrast to living cohorts with diagnosed DCM, no cases meeting autopsy criteria for DCM had a truncating/splice variant. Since non-survivors (i.e., SCDs) are underrepresented in DCM cohorts, our results suggest a potential role for non-A band TTN variants in arrhythmic risk.

Introduction: Level of activity has a reported association with sudden death, but cardiac causes are presumed by convention. We investigated association between activity level and causes of presumed SCD (pSCD) in the San Francisco POstmortem Systematic InvesTigation of Sudden Cardiac Death (POST SCD) Study. Methods: POST SCD is a prospective cohort study using autopsy, clinical records, and toxicology to adjudicate arrhythmic (potentially rescuable with implantable defibrillator) or non-arrhythmic (e.g., tamponade, overdose) causes among pSCDs (WHO defined) 18-90 years in San Francisco. We included all incident cases from 2/1/11-3/1/14 (n=525) and incident cases approximately every 3rd day from 3/1/14-12/31/21 (n=358). Activity level at time of pSCD was determined by forensic investigator reports. For unwitnessed deaths, activity level was inferred based on time of arrest and location found. Activity level was classified as: sleep, recently awoke (<10 min before death), awake with no activity (e.g., sitting), mild/moderate (e.g., bathing, feeding, walking), and rigorous (e.g., strenuous activity, sexual activity). Results: Of the total 883 pSCDs (mean 60 years, 73% male), 247 (28%) were sleeping, and 516 (58%) were awake at time of event. Cases with unclear circumstances (n=120, 14%) were excluded from analysis. Sleep was associated with non-cardiac cause of death (p=.01), specifically SUDEP (p=.02) and occult overdose (p<.001). Wakefulness was associated with SAD (p=0.005), pulmonary embolism (p=.007), and vascular damage (p=.004) (Table). Nearly all cases engaging in rigorous activity at time of death (n=32) were SADs (31/32, 97%) and male (29/32, 91%). Conclusions: Most sudden deaths in this 11-year countywide postmortem study occurred during wakefulness. Sleep was associated with non-arrhythmic cause (specifically SUDEP and occult overdose), while wakefulness and rigorous activity were associated with arrhythmic cause of sudden death.