Surgery for problems unrelated to the heart can damage heart cells — and it could be deadly for some patients, a new study finds.

A study published Monday in the American Heart Association’s journal Circulation found that heart cell damage that occurs during or after a non-heart-related operation was associated with an increased risk of death among patients who were 65 or older or who had a pre-existing heart problem.

Heart damage that develops during or after surgery is called perioperative myocardial injury, or PMI.

“Patients with PMI are easily missed because they show no symptoms of heart disease in the majority of cases and only very rarely experience chest pain, which is the typical symptom of heart attack,” said the study’s lead author Christian Puelacher, M.D., Ph.D., a clinical researcher at Cardiovascular Research Institute Basel in Switzerland, in a press release.

The study included more than 2,000 women and men who had heart disease or were at high risk of developing heart disease. All of the patients had non-heart-related surgery from 2014 to 2015 at the University Hospital Basel.

Some of the patients had procedures, like knee surgery, that are associated with a low risk of dying. Others had operations considered moderate risk, such as a hip replacement or gall bladder removal. Still others had more complicated, risky procedures, such as surgery to remove part of the lung or the liver.

To assess whether heart cell damage occurred during surgery, researchers measured the patients’ levels of troponin — a heart protein found in the blood — before and after their procedures. Using troponin to measure heart damage allowed the researchers to identify patients who had developed PMI, regardless of whether they displayed any of the typical symptoms.

Puelacher and his colleagues found that one out of seven patients who were 65 or older who had previously been diagnosed with coronary artery disease, peripheral artery disease or stroke developed PMI. These patients were six times more likely to die of any cause in the 30 days following their surgery than were patients who did not develop PMI. The high death rate associated with PMI persisted up to one year after surgery.

“Recognizing PMI as a potential contributor to death after surgery might help improve the outcomes of non-cardiac surgery,” Puelacher said. “However, since there are no clear treatment recommendations for these patients, treatment currently has to be tailored to each patient individually.”

The next step, he said, is to conduct research that “will identify optimal PMI management strategies following detection.”

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