The epidemiology of sudden cardiac deaths (SCDs) was turned on its head Thursday, with research showing that in reality, ischemic cardiac disease is not the leading driver of SCDs, as previously thought. [MEDPAGE TODAY]

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From a prospective autopsy study of unselected deaths in San Francisco County, California, it was evident that out of 943 presumed SCDs, 62% were autopsy-confirmed, and only 41% of those were due to myocardial infarction (MI) upon comprehensive postmortem and histologic evaluation -- "one-half the long-accepted 80% prevalence among SCDs," according to Zian Tseng, MD, MAS, of University of California San Francisco, and colleagues of the POST SCD study.

For the remaining 59% of autopsy-confirmed SCDs not traced to an MI, they can be explained by a range of causes including hypertensive heart disease, dilated cardiomyopathy, substance-related cardiomyopathy, and normal heart primary electrical disease. When an MI was involved, nine in ten cases were attributed to acute or healed MI with obstructive coronary artery disease, and one in ten related to acute MI with nonobstructive coronary arteries (MINOCA).

The study was presented at the annual meeting of the Heart Rhythm Society (HRS), held in Chicago this year. A full manuscript was published in the Journal of the American College of Cardiology.

Importantly, the countywide study did not rely on coronary angiographic data obtained from patients who survived the initial resuscitation, a source of potential selection bias in prior studies.

"For decades, MI was considered the leading cause of SCD," according to an accompanying editorial by Florence Dumas, MD, PhD, and Alain Cariou, MD, PhD, both of Paris Cité University, Inserm. "Consequently, most research and management efforts have been focused on MI as a cause of SCD."

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