The heart: Before, during and after COVID-19

As the coronavirus pandemic rapidly evolved into a public health crisis of global proportions, doctors and scientists embarked upon a real-time journey to uncover how the virus mercilessly attacks various parts of the body and what to do about it. While medical experts have been troubled by the respiratory virus’ tendency to wreak havoc on the lungs, perhaps more puzzling has been its relationship with the heart.

More than six months into the global pandemic, studies have shown that COVID-19 can not only exacerbate existing heart problems, but could also potentially cause new ones, causing experts to question whether the cardiac impacts of the virus may outlast the infection itself.

While not conclusive, case reports of long-term heart problems following COVID-19 infection are beginning to surface, including one from a New York City critical care physician who had mild symptoms of coronavirus but was later diagnosed with new heart disease.

"I started to feel like my heart was racing and I couldn’t run around like I always do and I had trouble catching my breath,” Dr. Janet Shapiro told NBC New York. It turned out she’d developed cardiomyopathy, a condition in which the heart struggles to pump blood to the rest of the body.

“What is clear is that we are still learning about this disease,” Dr. Shoeb Sitafalwalla, a cardiologist with Advocate Aurora Health in Illinois, told ABC News.

In the six months since the pandemic began, doctors have already learned a great deal about the toll COVID-19 takes on the heart during acute infection, but they still have a lot to learn about it’s long-term impact, Sitafalwalla explained.

Back in February, research from China found people with preexisting heart conditions were more likely to die of the infection, with the Chinese Center for Disease Control reporting a death rate four times the population's average. As the virus spread globally beyond China, this was followed by a smaller Italian study showing hospitalized COVID-19 patients with heart disease had approximately double the risk of death compared to those with previously healthy hearts, as well as markedly elevated risks of blood clots and septic shock.

More recently, a large-scale study out of Brigham and Women’s Hospital published last month corroborated the elevated risk of COVID-19 death internationally, finding in-hospital mortality rates of 10 to 15% depending on the underlying heart condition, approximately double the risk of those without these conditions.

Meanwhile, as data came in from around the world, the CDC offered official guidance that serious heart conditions can increase the risk of severe illness and death from COVID-19.

But what scientists and doctors saw next puzzled them.

In hospitals across the globe, young, healthy patients with no history of heart disease showed signs that COVID-19 had taken a hefty toll on the heart.

Given the recent discussion on safety in sports, some experts now say that athletes who have had COVID-19, particularly if severe, may need follow-up to evaluate their risk for playing sports, as viral inflammation of the heart can lead to sudden cardiac death. Parents and kids alike may need to consider safety guidelines.

By peering into the cells of COVID-19 patients, scientist are finding, according to an article in the Journal of the American Medical Association, that approximately 10-30% of people hospitalized with the virus show molecular evidence of new cardiac injury.

Interestingly, doctors point out that although these molecular signatures often indicate a patient will take a turn for the worse, they don't always spell disaster for the heart.

“So far the amount of cardiac injury has not been tremendous," said Dr. Sean Wu, cardiologist at Stanford Healthcare--meaning most people who develop these laboratory abnormalities do not necessarily end up having heart problems clinically. He contrasted this with other viruses known to infect the heart, like the Coxsackie B3 virus, which tend to cause problems as a result of inflammation in the heart muscle or “myocarditis” for months to years.

The autopsy findings of patients who died from the virus only seemed to deepen the mystery. New York City medical examiners recently reported,according to The Washington Post, that while their findings were consistent with doctors’ reports of SARS-CoV-2 related lung, kidney and liver damage, they surprisingly found little evidence of physical damage to the heart.

Regardless of the cause, recovery from the virus may not mean full recovery for the heart, warns Dr. Raul Mitrani, a University of Miami cardiologist who specializes in electrophysiology. In a new HeartRhythm report, he draws from a review of current literature and personal experience to offer guidance on the possibility of long-term COVID-19 cardiac sequelae including abnormal heart rhythms.

Experts like Mitrani are speculating that long-term heart damage might manifest in unexpected ways, potentially through scar tissue accumulation in the heart, and are highlighting “post-COVID-19 cardiac syndrome” as an important area for future research.

"We have developed a post-COVID Cardiac Clinic to screen patients for residual heart problems," said Mitrani.

But other experts say it's too early to know if long-term heart damage is likely to be a problem. Unlike Mitrani, Wu and his colleagues haven't yet seen anyone with persistent COVID-related heart problems after hospital discharge.

“I think because we’ve only seen COVID within the last few months we don’t have any longer term data in terms of how many people having had myocardial injury will end up requiring continued follow-up for those cardiac manifestations,” explained Wu. “I think we’re just a little early in terms of quite knowing how this will end up.”

What to know about the coronavirus:

• How it started and how to protect yourself: Coronavirus explained
• What to do if you have symptoms: Coronavirus symptoms
• Tracking the spread in the U.S. and worldwide: Coronavirus map

Tune into ABC at 1 p.m. ET and ABC News Live at 4 p.m. ET every weekday for special coverage of the novel coronavirus with the full ABC News team, including the latest news, context and analysis.

Jessica Johnson, M.D. is a senior resident in emergency medicine at Stanford University and contributor to the ABC News Medical Unit. Jay Bhatt, D.O. is a practicing internist, Aspen Health Innovators Fellow and ABC News contributor.