Myocarditis: Causes, Symptoms and Treatments

It seems like we have been in the midst of the COVID-19 pandemic forever, but in reality the disease has been around for less than one year. That’s not a long time, as far as new diseases go, and scientists are learning more and more about it all the time. Indeed, given this relatively short timespan, it’s hard to know what the long-term effects of the coronavirus may be. However, clinicians and researchers are noticing a connection between COVID-19 and heart disease.

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In particular, patients infected by the novel coronavirus often develop a worrisome inflammation of the heart muscle. Known as myocarditis, this inflammation potentially can produce serious heart disease. In a July 2020 study published in JAMA Cardiology, researchers discovered that 78 out of 100 patients recovering from COVID-19 had some kind of cardiac impairment, and 60 of those had myocarditis after recovering, independent of whether or not they had preexisting conditions or how severe their COVID-19 symptoms were.

“We were not expecting that,” says Dr. Sandra Chaparro, a cardiologist at the Miami Cardiac and Vascular Institute who specializes in heart failure and transplantation cardiology and serves as the director of advanced heart failure. That study’s small sample size makes it hard to know just how widespread the incidence of myocarditis really is, she says. But anecdotal evidence from around the world – including at her institute, which has treated several patients with the condition – suggests it’s worth monitoring.

“We’ve seen it in young and old patients,” Chaparro says. One patient in his 40s recovered from COVID-19 but had signs of heart damage after. However, the connection is still far from clear. “Sometimes it’s hard to figure out if it was caused by something else or a preexisting condition. And we don’t know what the rate (of myocarditis) is of asymptomatic patients,” she adds. But the data and case studies are raising alarms.

What Is Myocarditis?

Myocarditis is any inflammation of the heart muscle, says Dr. Karol Watson, a cardiologist and a professor of medicine/cardiology at the David Geffen School of Medicine at UCLA. This inflammation can have many causes. A virus like the coronavirus is one of the most common causes, but bacterial infections, chemotherapy drugs or a dysfunctional immune system may also be behind it.

Myocarditis can disrupt the heart’s ability to pump blood and impair the electrical signaling that keeps it beating regularly. It can be mild, and most people do not have a lot of symptoms, if any, Chaparro says. In severe cases, myocarditis can cause abnormal heart rhythms, heart muscle disease and heart failure. These patients may need medication and/or mechanical support, like heart pumps, and a small number of patients require heart transplant, she says.

How Does COVID-19 Affect the Heart?

The coronavirus may cause inflammation in up to three ways. “Like any virus, it can directly attack the heart muscle, causing inflammation and myocarditis,” says Watson, who is also director of the UCLA Women’s Cardiovascular Health Center and the UCLA-Barbra Streisand Women’s Heart Health Program. Heart cells have receptors to which the virus can attach and cause direct myocardial injury, Chaparro concurs.

Second, the virus can also infect the lungs, which become impaired and fail to deliver the amount of oxygen needed to feed the heart. When respiration fails and oxygen levels are too low – called hypoxemia – the overworked and underfed heart may become inflamed.

Third, the coronavirus can, in severe cases, cause what’s known as a cytokine storm, an overreactive immune system response that causes inflammation throughout the body, including the heart. “It is the extreme manifestation of inflammation,” Watson says.

Role of Preexisting Conditions

Watson says that many cardiac conditions follow a “two-hit” hypothesis. “They may have one hit, which is hypertension or obesity or something else. Then when a second hit comes along, such as COVID, the severe manifestations are expressed,” she says. This is why those with preexisting conditions that affect the heart, such as diabetes, obesity, high blood pressure, age and others, are at such higher risk of death than those without such conditions. However, remember that the German study found that even those with no preexisting conditions could develop myocarditis.

Signs of Myocarditis

Many cases of myocarditis are asymptomatic, Watson says. Some of the signals of myocarditis, according to the Mayo Clinic, include:

  • Chest pain.
  • Rapid or abnormal heart rhythms, or arrhythmias.
  • Shortness of breath, at rest or during physical activity.
  • Fluid retention with swelling of your legs, ankles and feet.
  • Fatigue.
  • Other signs and symptoms of a viral infection, such as a headache, body aches, joint pain, fever, a sore throat or diarrhea.

Physicians test for myocarditis with imaging studies such as electrocardiograms and echocardiograms. Blood tests also may reveal biomarkers, chemicals that reveal heart muscle damage or heart failure, Chaparro says.


Treatment depends on the symptoms. “If asymptomatic, no specific treatment besides rest may be given,” Watson says. If the heart function is severely damaged, then treatment consists of:

  • Supporting the heart, which may include medication or require advanced therapies such as mechanical circulatory support.
  • Controlling the inflammation, often with powerful anti-inflammatory medications like steroids.
  • Protecting the heart with medications such as ACE inhibitors or beta blockers.

Prevention, of course, is the best medicine. Chaparro urges everyone to use “the most important tools we currently have to prevent infection,” including wearing a mask, practicing social distancing, washing your hands often and getting a flu shot to reduce the risk of a co-infection.

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