Abstract Body (Do not enter title and authors here): 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.