A growing number of studies suggest many COVID-19 survivors experience some type of heart damage, even if they didn’t have underlying heart disease and weren’t sick enough to be hospitalized. This latest twist has health care experts worried about a potential increase in heart failure.

“Very early into the pandemic, it was clear that many patients who were hospitalized were showing evidence of cardiac injury,” said Dr. Gregg Fonarow, chief of the division of cardiology at the University of California, Los Angeles. “More recently, there is recognition that even some of those COVID-19 patients not hospitalized are experiencing cardiac injury. This raises concerns that there may be individuals who get through the initial infection, but are left with cardiovascular damage and complications.”

Fonarow said these complications, such as myocarditis, an inflammation of the heart muscle, could lead to an increase in heart failure down the road. He’s also concerned about people with pre-existing heart disease who don’t have COVID-19 but who avoid coming into the hospital with heart problems out of fear of being exposed to the virus.

“The late consequences of that could be an increase in heart failure,” he said. “It is much safer if having symptoms that could represent heart attack or stroke, to come into the emergency department than to try to ride it out at home.”

Nearly one-fourth of those hospitalized with COVID-19 have been diagnosed with cardiovascular complications, which have been shown to contribute to roughly 40% of all COVID-19-related deaths.

But two recent studies suggest heart damage among those infected may be more widespread. In JAMA Cardiology, an analysis of autopsies done on 39 COVID-19 patients identified infections in the hearts of patients who had not been diagnosed with cardiovascular issues while they were ill.

Another JAMA Cardiology study used cardiac MRIs on 100 people who had recovered from COVID-19 within the past two to three months. Researchers found abnormalities in the hearts of 78% recovered patients and “ongoing myocardial inflammation” in 60%. The same study found high levels of the blood enzyme troponin, an indicator of heart damage, in 76% of patients tested, although heart function appeared to be generally preserved. Most patients in the study had not required hospitalization.