Prevalence of concealed arrhythmogenic substrate for sudden cardiac arrest in the general population

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: Public grant(s) – National budget only. Main funding source(s): US National Heart Lung and Blood institute National Institute of Health. BACKGROUND: Individuals who present with SCA as the first manifestation of heart disease (Concealed Substrate) present the greatest challenge for clinical risk stratification but population-based information in the current era is lacking. We hypothesized that improved awareness and access to health care has resulted in a reduction in prevalence of Concealed Substrate. PURPOSE: We compared the overall prevalence, secular trends and SCA etiologies of Concealed Substrate in two geographically distinct US populations. METHODS: Consecutive cases of SCA were ascertained prospectively from 2 large ongoing US studies, the Population Cohort A (PopulationCohortA, 2002-2018) and Population Cohort B (PopulationCohortB, 2015-2022), total population 1.85 million residents. All out-of-hospital SCA events attended by emergency medical services were determined following an established multi-source ascertainment and adjudication process, and detailed lifetime clinical record evaluation conducted for each individual. This included the comprehensive electronic health record, evaluation of SCA survivors as well as all available autopsy information. Concealed Substrate cases were defined as SCA with no prior heart disease diagnosis. RESULTS: From a total of 5708 SCA cases (age 66.5 ± 18.2, female 35%), n=3390 (age 64.3 ± 18.8, female 34%) were identified in PopulationCohortA and n=2318 (age 71.6 ± 15.7, female 36%) in PopulationCohortB. In PopulationCohortA, prevalence of Concealed Substrate was 39% (n=1282, age 58.6 ± 21.7, 32% female) and decreased modestly over time (Figure; 37% in 2002-06 vs. to 33% in 2014-18; p=0.001). In PopulationCohortB, overall prevalence of Concealed Substrate was 41% (n=949, age 68.3 ± 17.6, 33% female) and did not change significantly over time (Figure; 2015-2022; p=0.06). Etiology of SCA was determined in a subgroup of overall cases (n=3210, 56%) of which n=2727 (85%) were ischemic SCA and n=483 (15%) non-ischemic SCA. Non-ischemic SCA was more commonly identified in Concealed Substrate (29% vs. 11%; p<0001) and ischemic SCA was more common in Revealed Substrate (89% vs. 72%; p<0.0001). CONCLUSION: There was a modest reduction in prevalence over time, 33-41% of individuals continued to present with Concealed Substrate, with higher likelihood of non-ischemic SCA. These findings suggest that widely available and inexpensive tests such as the 12-lead ECG warrant further evaluation as a pre-screening method in the general population. [Figure: see text]