The community burden of sudden cardiac death (SCD) was the topic of two separate studies presented at HRS 2026 and simultaneously published in JACC.

As part of the Postmortem Systematic Investigation of Sudden Cardiac Death (POST-SCD) study, Kosuke Nakasuka, MD, PhD, and Jakrin Kewcharoen, MD, et al., explored the total burden of community SCD attributable to myocardial infarction (MI) in patients with obstructive and nonobstructive coronary arteries over 12 years in San Francisco County.

Results found that of 943 presumed SCDs between 2011 and 2023, 360 (38%) were the result of noncardiac causes, while 583 (62%) were autopsy-confirmed SCDs. Of the confirmed SCDs, 237 (41%) were due to MI, 23 (10%) of which were due to acute MI with nonobstructive coronary arteries (MINOCA).

In other findings, Nakasuka and colleagues found the right coronary artery to be the "most common culprit in acute MI with obstructive coronary artery disease (MI-CAD). Nonarrhythmic deaths were twice as common in MINOCA (35%) than acute MI-CAD SCDs (15%). Total fibrosis burden was similar in MINOCA and acute MI-CAD SCDs, they said. Black individuals had the highest proportion of deaths from MINOCA (27%), according to the study investigators.

"These findings suggest refined SCD risk stratification is needed beyond the traditional focus on arrhythmic causes and coronary atherosclerosis, especially left-sided disease," write Nakasuka, et al.

In another study, also using data from POST-SCD, James W. Salazar, MD, MAS, and Nakasuka, et al., assessed SCD in relation to previously diagnosed or occult cardiac disease at autopsy. "SCD prevention focuses on individuals with diagnosed disease [i.e., conventional SCD risk factors] such as reduced ejection fraction (EF) and MI," they write. "The burden of occult disease among community SCDs without diagnosed risk factors is unknown and represents a target for prevention via increased detection."

Study results found that of 877 presumed SCDs, 58% (n=513) were autopsy-defined arrhythmic deaths, of which 32% (n=166) had diagnosed risk factors. The mean age was 64 years and 77% were male. Of the remaining arrhythmic deaths, 31% (n=159) had occult MI or dilated cardiomyopathy with similar demographics and cardiac pathologies, including fibrosis and coronary diseases, as those with risk factors. Another 36% (n=185) were younger (average age of 57 years) with less cardiac pathology than those with occult MI or dilated cardiomyopathy, researchers said.

"In this 12-year countywide postmortem study, two-thirds of community arrhythmic SCDs occurred in individuals without diagnosed disease despite substantial cardiac pathology," said Salazar and colleagues. "... These findings suggest that improved detection of occult cardiac disease is a critical priority to reduce community sudden deaths."

In a related editorial comment by Florence Dumas, MD, PhD, and Alain Cariou, MD, PhD, explain, "These findings must now be taken into account, and collective reflection is needed on the measures to be implemented. The use of modern tools, combining, for example, the integration of physiological signals from connected devices (smartwatches, cell phones) with continuous analysis facilitated by artificial intelligence, could be a promising avenue for detecting hidden heart conditions. Similarly, strengthening screening programs in schools, sports, and workplaces is likely a path worth encouraging."