More than half of heart attacks in people under 65 are not due to blocked arteries.

Many heart attacks that occur in people under 65, especially women, are not caused by narrowing of the arteries caused by fatty buildup ( atherosclerosis ), calling into question traditional assumptions about how heart attacks occur in younger people.

A study, published in the Journal of the American College of Cardiology , concludes that more than half of heart attacks in women under 65 were caused by non-traditional factors, such as spontaneous coronary artery dissection (SCAD), embolism - when a clot travels from where it formed to another location in the body - and other conditions unrelated to atherosclerosis or blockage of the arteries by plaque.

Analysis of more than 15 years of data from the Rochester Epidemiology Project showed that the incidence of heart attacks was significantly lower in women than in men, but when women suffered heart attacks, the underlying causes were often misdiagnosed.

Spontaneous coronary artery dissection (SCAD) is a sudden tear in the wall of a coronary artery that reduces or blocks blood flow to the heart , which can cause a heart attack or sudden death. It primarily affects young, healthy women without traditional risk factors such as high cholesterol.

Until now, it was often overlooked and misclassified as a typical heart attack due to plaque buildup.

The most common cause of heart attacks in both sexes was atherosclerosis, or plaque that clogs arteries, but this only accounted for 47% of heart attacks in women, compared to 75% in men.

Five-year mortality rates were higher in people who suffered heart attacks triggered by stressors such as anemia or infections, even though these patients had lower levels of heart damage.

In the study, of the 1,474 heart attacks analyzed, 68% were attributed to the typical plaque buildup associated with traditional heart disease; however, nontraditional causes predominated in women. Among these, spontaneous coronary artery dissection was nearly six times more common in women than in men. Heart attacks triggered by stressors, such as anemia or infection , were the second most common cause overall and were the most deadly, with a five-year mortality rate of 33%. In contrast, truly unexplained heart attacks were rare, accounting for less than 3% of cases after expert review.

"This research highlights the causes of heart attacks that have historically been underestimated, especially in women," said Claire Raphael of the Mayo Clinic and first author of the study. "When the underlying cause of a heart attack is misunderstood, less effective or even harmful treatments may be used."

This new understanding could save lives .

For example, a misdiagnosed SCAD may be treated with a stent unnecessarily, increasing the risk of complications. Correctly recognizing and diagnosing these nontraditional strokes allows for more appropriate care and better long-term outcomes.

The authors note that their study provides information that could change the way heart attacks are diagnosed and treated in young adults.

Overall, the study provides information that could change the way heart attacks are diagnosed and treated in young people, especially women.

"Our research highlights the critical need to rethink how we approach heart attacks in this patient population , particularly in young adult women. Clinicians need to heighten their awareness of conditions like SCAD, stroke, and stress-related triggers, and patients need to demand answers when something doesn't feel right," said Rajiv Gulati, senior author of the study.

"Understanding why a heart attack occurred is just as important as treating it," Raphael concludes. "It can make the difference between recovery and recurrence."