Key result
Hypertrophic cardiomyopathy was associated with a higher proportion of arrhythmic cause among presumed sudden cardiac deaths compared to those without HCM (85% vs. 54%, P=0.03).
Why the study?
Reported SCD incidence in HCM presumes an arrhythmic cause and misses occult cases dying before diagnosis.
Cohort (n=1,022)
No
Absolute Event Rate: 85% vs 54%
p-value: p=0.03
Hypertrophic cardiomyopathy accounts for 2% of sudden arrhythmic deaths up to age 90, with 85% of cases undiagnosed prior to death, suggesting the true burden of HCM-related sudden death is substantially underestimated.
AIMS: Incidence of sudden cardiac death (SCD) is 1%/year in cohorts with hypertrophic cardiomyopathy (HCM), but this estimate presumes arrhythmic cause and misses occult cases dying before diagnosis. METHODS AND RESULTS: POST SCD (POstmortem Systematic InvesTigation of Sudden Cardiac Death) is a prospective cohort study using autopsy, clinical records, and toxicology to adjudicate arrhythmic or non-arrhythmic causes among presumed SCDs (pSCDs) meeting WHO criteria aged 0-90 years in San Francisco County. We included all incident cases 2/1/2011-3/1/2014 (n = 525) and approximately every third day 3/1/2014-9/1/2022 (n = 497) based on medical examiner call schedule. We identified HCM victims via three approaches: (i) pathology; (ii) echocardiogram [transthoracic echocardiogram (TTE)]; (iii) genetic criteria. Incidence calculations used county data and estimated HCM prevalence of 1:500 from studies of persons aged 23-35 years old. Of 1022 pSCDs [558 (54.6%) arrhythmic deaths] during the study period, 13 had HCM: 10 met pathology criteria; 2 via review of 203 TTEs (missed on initial report); 1 via genetic testing. Of these, 11 were arrhythmic deaths, yielding 1.3% burden of sudden death (pSCD) and 2% of arrhythmic death. Only 2 of 13 (15%) pSCDs with HCM had pre-mortem diagnosis. Incidence for persons with HCM 18-35 years old was 0.2% pSCDs/year and 0.1% SADs/year. pSCDs with HCM had a higher proportion of arrhythmic cause [11/13 (85%) vs. 547/1009 (54%), P = 0.03] than those without. pSCD burden due to HCM decreased with age (P = 0.003), highest among victims <35 years old, for whom HCM accounted for 7.1% of pSCD and 9.4% of arrhythmic death. Genetic testing of 317 consented pSCDs yielded pathogenic or likely pathogenic variants in 40% (2/5) and identified one additional case without clinical phenotype. CONCLUSION: In this 11-year countywide post-mortem study, HCM meeting pathologic, clinical, or genetic criteria was associated with autopsy-confirmed arrhythmic cause of sudden death, accounting for 2% of SADs up to age 90, highest in cases <35 years old. Since 85% of cases were undiagnosed before pSCD, the true burden of HCM-related sudden death may be substantially underestimated.
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Haghighat et al. (2025) conducted a cohort in Sudden cardiac death and hypertrophic cardiomyopathy (n=1,022). Hypertrophic cardiomyopathy (HCM) vs. No HCM was evaluated on Arrhythmic cause of sudden death (p=0.03). Hypertrophic cardiomyopathy was associated with a higher proportion of arrhythmic cause among presumed sudden cardiac deaths compared to those without HCM (85% vs. 54%, P=0.03).
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