In a new study from Duke Medicine, researchers have found that in more than half of patients who suffer from STEMI, a deadly kind of heart attack caused by a blocked artery, one or both of the patient’s other arteries were also obstructed.  

This finding brings to question whether and when additional artery clearing procedures should be undertaken.

The study, the first large analysis of how often these secondary blockages occur— either at the same time or within a few days or weeks— also found that they lead to worse outcomes for patients. Scientists previously believed that patients would have additional blockages, but the findings indicated the prevalence.

“We assumed this was a common problem, but it has not been well understood or quantified,” senior author Dr. Manesh Patel, director of interventional cardiology and cardiac catheterization labs at Duke University Health System said in a news release.“We found that more than half of the 28,000 patient scans we analyzed showed at least one additional blocked artery, and about 19 percent had blockages in all three arteries.”

Researchers analyzed data from eight large, international clinical trials of patients who had suffered a STEMI heart attack— ST segment elevation myocardial infarction. According to the American Heart Association, this serious heart attack affects nearly 250,000 people in the U.S. annually.

Additionally, their findings showed that additional clogged arteries were associated with a small, but significant, increase in death rates— patients with more than one blocked artery had a 3.3 percent mortality rate within 30 days of a STEMI, compared to 1.9 percent among those who had one blockage.

“The current thinking among cardiologists is that it is dangerous to treat these other blockages at the same time as treating the artery that created the heart attack,” Patel said. “There has been a sense that the patient is healing and it may damage the heart. But we haven’t had a good idea of the risks or the potential benefits.”

Researchers concluded that additional studies are needed to confirm their findings and determine the best time and method for opening additional arteries to restore blood flow.