From the images of cloudy chest scans and gasping patients hooked up to ventilators, we’ve been conditioned to think of Covid-19 as a respiratory disease. But it’s not just about the lungs. Even from the early days of the pandemic, doctors were finding that a novel coronavirus infection could ravage other parts of the body, including the brain, blood vessels, and heart. Data from initial outbreaks in China, New York City, and Washington state suggested that 20 to 30 percent of patients hospitalized with Covid-19 showed signs of cardiac injury.
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That these patients tended to get sicker and died more often than patients without cardiac complications didn’t set off immediate alarm bells. These were, after all, people with serious cases of Covid-19—serious enough to wind up in the hospital. Most people who contract the virus experience a spectrum of less-severe symptoms. As many as one in three never feel sick. But now, evidence is emerging that the virus can cause heart damage even in people who’ve had mild symptoms or none at all, especially if those people exercise while they’re infected.
Last month, when league commissioners from the Big Ten and Pac-12 college conferences announced they would be postponing the 2020 fall sports season, one of the major factors they cited were concerns over something called myocarditis. That’s cardiologist-speak for what happens when the muscular walls of the heart become inflamed, weakening the organ and making it more difficult for it to pump blood. It’s not a newly discovered condition, and it turns up pretty rarely, but when it does, it’s most often triggered by an infection. Viruses, bacteria, even invading amoebas, yeasts, and worms have all been shown to cause it.
What they have in common is that they jolt the body’s immune system into attack mode, leading to inflammation. If a person rests while they are ill and during recovery, most of the time the inflammation recedes and the heart muscle heals on its own. But strenuous activity while the heart is weakened can cause swelling in the legs, dizziness, shortness of breath, and—in serious cases—irregular heartbeat, cardiac arrest, and sudden death.
These more extreme outcomes are seen most often in competitive athletes. That’s why cardiologists have been urging caution about the return of sports mid-pandemic. Just last month, former Florida State basketball player Michael Ojo died of apparent heart complications while playing in a pro league in Serbia, shortly after the 27-year-old had recovered from Covid-19.
To prevent the pandemic from leading to similarly tragic heart injuries among student athletes, doctors at Ohio State University developed a new protocol, says Saurabh Rajpal, a cardiologist and assistant professor of internal medicine at OSU. The protocol requires any player diagnosed with Covid-19 to receive a clinical examination, blood test, electrocardiogram, and MRI—a costly and sparingly used imaging technology—before returning to play. Between June and August, 26 men and women from the school’s football, soccer, lacrosse, basketball, and track teams showed up to be screened after having recovered from Covid-19. MRIs turned up inflammation of the heart muscle—a sign of myocarditis—in four of them. Of those, two had never experienced any symptoms of Covid-19. The case series was reported Friday in the journal JAMA Cardiology.
Because the athletes’ hearts weren’t imaged prior to their Covid-19 infections, and because they weren’t matched with controls—similar people who didn’t contract the virus—it’s impossible to say for sure whether the virus caused the observed damage. But Rajpal, one of the study’s coauthors, says that other viral infections cause myocarditis, and SARS-CoV-2 is no different. “It’s important for people to know that Covid-19 can affect the heart,” he says.
And these problems don’t just affect athletes. A larger observational study conducted in Germany earlier this summer followed 100 non-athlete Covid-19 patients and found lingering heart inflammation and other cardiac abnormalities in 78 of them. According to Eric Topol, a US-based cardiologist who corresponded with the study’s authors, 12 of those people had no symptoms of Covid-19 at all. And while the study was later corrected for statistical errors, its authors confirmed that the main conclusions still stood: Even a mild course of Covid-19 could harm the heart.
Exactly how much and how often, well, nobody knows that yet, says Topol, who directs the Scripps Research Translational Institute in La Jolla, California. “That’s an uncharted frontier,” he says. The evidence is still mostly anecdotal. He’d like to see governments and other research funders setting aside money to more systematically study large cohorts of people to see what happens to their hearts after they get Covid-19. But so far, it doesn’t seem like much of a priority. Maybe that’s because lots of other viruses can also cause myocarditis, speculates Topol. But the difference here—and what should be spurring more urgent study, he believes—is that most viruses don’t infect tens of millions of people in the span of six months.
“In the US right now, estimates are that over 50 million people have been infected with this virus,” he says. (There have been 6.5 million confirmed cases, but due to the US’ flailing testing infrastructure, experts estimate the real number is closer to 10 times that.) Even if only 1 percent of Americans experience some kind of heart issue, that’s still 500,000 people. “That’s what people are losing here,” says Topol. “It doesn’t take much incidence when this virus has been through so many people to be a huge burden. That’s why we need to get our arms around this and understand this as soon as possible. “
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Scientists also still don’t know if the inflammation observed in Covid-19 patients is collateral damage from the body’s immune response or the virus directly infecting heart tissue. Cardiac muscle cells do express ACE2, the molecular doorway that the coronavirus uses to invade new hosts. And autopsy studies have discovered the virus inside the hearts of deceased Covid-19 patients. (Though, notably, not the kinds of immune cells associated with an inflammatory response.) Earlier this month, scientists at the San Francisco–based Gladstone Institutes found that the virus, when added to human cardiac cells in a petri dish, shredded the long muscle fibers that keep hearts beating. Bruce Conklin, one of the study's’s coauthors, told STAT the “carnage” was unlike anything that’s ever been seen with other diseases. But more research is needed to better understand if that’s representative of what’s actually happening inside the bodies of people with Covid-19 infections.
The need is especially critical because so many people who get infected with the coronavirus don’t know it. And they might unwittingly do things—like exercising—that could damage their hearts during or immediately after their infection. Amateur athletes especially, like marathoners, ultrarunners, triathletes, and others who clock a lot of miles but don’t have access to regular cardiac screenings, might not be aware enough of the risks to make judgments about the safety of their training regimens.
That’s why Rajpal suggests paying extra-close attention to your body if you’re going out for a hard run, bike ride, or other sporting activity, especially if you have any inkling of sickness. “If you experience any suspicious symptoms—chest pain, shortness of breath, or heart palpitations—contact your doctor,” he says. And if you have tested positive for Covid-19, he says, you should take a few weeks off before returning gradually to the level of training you were at before.
At OSU, the athletes who showed signs of myocarditis on their MRIs have been put on a mandatory three-month rest. At the end of that, they’ll be rescanned to make sure the inflammation has subsided, and only then, says Rajpal, will they be cleared to play.
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