Causes of Heart Inflammation

August 12, 2021

Clinical Contributors to this story:
Steven Hollenberg, M.D.

Updated: 01/27/2022

Because myocarditis – a type of heart inflammation – has made headlines lately as a very rare side effect of certain COVID-19 vaccines, you may be wondering what heart inflammation is and what causes it.

Heart inflammation is commonly caused by infections, including viruses or bacteria, although it may also occur in response to other factors, such as an autoimmune disease or certain medications. Mild cases may resolve on their own, but people may need medication or a medical procedure to alleviate the condition. Seeing a doctor when you experience symptoms like fever, chest pain and shortness of breath should help you get the care that you need.

“Heart inflammation is rare, but it has been talked about in the news more often in the past year-and-a-half because of the pandemic,” says Steven Hollenberg, M.D. “Some people who were infected with COVID-19 have experienced heart inflammation as a complication. More recently, heart inflammation has surfaced as a rare side effect after COVID-19 vaccination.”

There are three different types of heart inflammation:

  • Myocarditis, which is inflammation of the heart muscle
  • Pericarditis, which is inflammation of the sac that surrounds the heart
  • Endocarditis, which is inflammation of the inner lining of the heart, including the surface of the heart valves

The type of heart inflammation that has been associated with COVID-19 vaccines is myocarditis, inflammation of the heart muscle itself. Both myocarditis and pericarditis have been associated with COVID-19 illness.

Causes of heart inflammation

There are a number of causes of heart inflammation. The most common are:

  • Viral infections, including enteroviruses, mononucleosis, HIV and COVID-19
  • Bacterial infections, such as strep, staph and Lyme disease
  • Fungal infections, particularly among people with weak immune systems
  • Parasites, including toxoplasmosis and Chagas disease
  • Autoimmune diseases, including rheumatoid arthritis and lupus
  • Antibiotics
  • Anti-seizure medication
  • Some cancer medications
  • Following a heart attack, heart surgery or cardiac trauma
  • Certain vaccines

The link between COVID-19 and heart inflammation

Viruses are the most common cause of myocarditis. During the pandemic, some people with COVID-19 – which is caused by the virus SARS-CoV-2 – have experienced this type of heart inflammation as a complication of their illness. Researchers believe that this can happen for one of two reasons: direct injury to the heart muscle from the virus and/or cardiac damage because of the immune system reaction to COVID-19.

In June 2021, the Centers for Disease Control and Prevention reported that the Vaccine Adverse Event Reporting System had received more than 1,000 reports of heart inflammation – myocarditis and pericarditis – after Americans had received COVID-19 vaccines. More than 177 million Americans received COVID-19 vaccines during that time frame, which means that 0.0006 percent of all vaccinated people have had this reaction.

People who experienced heart inflammation after receiving a COVID-19 vaccine were more likely to be:

  • Male
  • Adolescents age 16 or older
  • Young adults

Heart inflammation was more likely to occur in people who received mRNA COVID-19 vaccines (Pfizer or Moderna), usually within a few days of the second vaccination. Most people who were treated improved quickly and were able to resume their usual activities.

Public health experts still recommend that all people aged 12 and older get COVID-19 vaccines, because the benefits outweigh this potential risk, which is very small.

“It is very unlikely that a single individual – even a male adolescent or young adult – who gets a COVID-19 vaccine will experience this complication, and almost all of the cases have been mild” says Steven Hollenberg, M.D. “Protecting yourself from COVID-19 should be your first concern.”

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The material provided through HealthU is intended to be used as general information only and should not replace the advice of your physician. Always consult your physician for individual care.

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