(CNN) As athletes recover from Covid-19, taking images of their hearts to screen for inflammation may help doctors determine when it could be safe to get back in the game, new research suggests.
The small study -- conducted by researchers at Ohio State University -- found in cardiac magnetic resonance images, or MRIs, that among 26 of the university's competitive athletes who were recovering from Covid-19, four showed signs of inflammation of the heart muscle, called myocarditis.
"Our objective was to investigate the use of cardiac magnetic resonance (CMR) imaging in competitive athletes recovered from COVID-19 to detect myocardial inflammation that would identify high-risk athletes for return to competitive play," the researchers wrote in a research letter published in the journal JAMA Cardiology on Friday.
The researchers performed cardiac magnetic resonance imaging on 26 competitive athletes referred to the university's sports medicine clinic after testing for Covid-19 between June and August. The athletes were involved in football, soccer, lacrosse, basketball and track -- and none had illness severe enough to require hospitalization.
Only 12 athletes reported having mild symptoms, such as sore throat, shortness of breath or fever, while others did not show any symptoms, according to the study.
The cardiac imaging was performed after each athlete quarantined for at least 11 days.
The imaging showed that four athletes, or 15%, had findings consistent with myocarditis and eight additional athletes, or 30.8%, had signs of prior myocardial injury. It's unclear from this study if this inflammation will resolve itself or produce lasting damage.
"Cardiac magnetic resonance imaging has the potential to identify a high-risk cohort for adverse outcomes and may, importantly, risk stratify athletes for safe participation because CMR mapping techniques have a high negative predictive value to rule out myocarditis," the researchers wrote. "CMR may provide an excellent risk stratification assessment for myocarditis in athletes who have recovered from COVID-19 to guide safe competitive sports participation."
The study had some limitations, including that the doctors do not have a baseline image of the athletes' hearts before they had Covid-19. There was also no control group of students who had not had Covid-19.
More research is needed to determine whether similar findings would emerge among a larger group of college athletes from various universities.
Over the summer, Ohio State was among several schools reporting Covid-19 cases within their athletic programs. Ohio State is part of the Big Ten conference, which has announced that it would be postponing all fall sports.
Even before the coronavirus pandemic, it has been recommended that athletes with a probable or definite diagnosis of recent myocarditis not participate in competitive sports while active inflammation is present. This kind of inflammation can weaken the heart, and if it is a severe case, it can lead to heart failure and sudden death.
Some research before the pandemic estimated acute myocarditis and other forms of heart muscle inflammation to be the cause of sudden cardiac death in 5% to 25% of athletes.
The American Academy of Pediatrics announced on Friday that its interim guidance for children and teens who participate in sports has been updated, clarifying that athletes with moderate symptoms of Covid-19 should show no symptoms for at least 14 days and obtain clearance from their primary care physicians before returning to exercise, practice and competitions.
Young athletes who had moderate symptoms of Covid-19 -- such as prolonged fever -- should get electrocardiograms taken of their hearts, and potentially be referred to a cardiologist for further assessment, according to updated guidance.
The updated guidance notes that an electrocardiogram, or EKG -- which records the electrical signals in your heart -- can help physicians determine whether a patient is well enough to return to sports activities.
"Exercise and sports offer so many health benefits to youth, and we know that many are eager to return to play," Dr. Susannah Briskin, one of the authors of the guidance, said in a news release on Friday. "We have many suggestions on how to reduce the risks, and they require being candid and forthcoming about anyone who is feeling unwell. Parents, children and coaches need to make safety protocols a priority."
The guidance also recommends that young athletes who have been potentially exposed to the coronavirus, regardless of whether they show symptoms, should sit out from all practices and games for a minimum of 14 days. It is also recommended that if an athlete tests positive for coronavirus, team officials and health departments should be notified so contact tracing and appropriate quarantining can be performed.