Many who have died of cardiac arrest may have had undetected heart attacks, study says

LOS ANGELES - Not all heart attacks are the same -- some of them are characterized as silent, meaning they can occur with atypical symptoms or no symptoms at all, and new research reveals a strong association between these silent heart attacks and sudden cardiac death.

In other words, many people who have died of sudden cardiac arrest may have had an undiagnosed or unnoticed heart attack at some point earlier in their life.

Sudden cardiac arrest, not to be confused with a heart attack, refers to the abrupt loss of heart function, breathing and consciousness that most typically results from an electrical disturbance in the heart that causes it to stop pumping blood to the rest of the body. If not caught and reversed with a defibrillator within minutes of onset, death will occur.

Sudden cardiac arrest is the third leading cause of death in the U.S., affecting people of all ages and resulting in about 356,000 deaths annually, according to the Sudden Cardiac Arrest Foundation.

A team of researchers set out to determine the prevalence of silent heart attacks, medically referred to as silent myocardial infarction (SMI), in individuals that had suffered sudden cardiac death and found a substantial link between the two.

The results were published in the JAMA Cardiology journal Wednesday.Researchers from Oulu University Hospital in Finland and University of Miami Miller School of Medicine compared the autopsy findings, clinical characteristics and EKG markers linked to SMI of a group of 3,122 individuals who had died of sudden cardiac arrest without any prior diagnosis or knowledge of coronary artery disease.

The study population was pulled from a prior Finnish study that examined arrhythmic events in a cohort of individuals who were found to have suffered sudden cardiac death in Northern Finland between 1998 and 2017.

Of the total 4,392 individuals who were determined to have had sudden cardiac death as a result of coronary artery disease, 3,122 of them had never been diagnosed with coronary artery disease.

They found that 42.4 percent of them, or 1,322 individuals, had scarring present during their autopsies which indicated SMI had occurred in the past.

In a separate study that examined similar data for a cohort of individuals in Minneapolis who had suffered sudden cardiac death between 2001-2004, 34 percent of individuals showed scarring consistent with SMI during autopsy. Those findings were published in the American Heart Journal in 2010.

Both studies point to a need for improved detection and treatment of coronary heart disease.

Identifying those individuals who are at risk of sudden cardiac death has historically been a challenge for medical professionals, but finding a way to accurately diagnose and treat SMI's could lead to a significant reduction in sudden cardiac death occurrences.