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What Is Myocarditis?

The muscle that makes up the heart is called the myocardium (my-uh-KAR-dee-em). Myocarditis is when this muscle gets inflamed (swollen).

Most children recover fully, but myocarditis can be serious.

What Happens in Myocarditis?

Myocarditis (my-uh-kar-DYE-tiss) can damage the heart. This damage can make it harder for the heart to pump blood and can cause abnormal heartbeats (arrhythmias).

What Are the Signs & Symptoms of Myocarditis?

Symptoms of myocarditis can vary. Some people have no symptoms. 

Signs in children with the condition include:

  • tiredness
  • fast breathing or trouble breathing
  • chest pain
  • heart palpitations (feeling of the heart fluttering)
  • lightheadedness
  • passing out

What Long-Lasting Problems Can Happen From Myocarditis?

Most children recover fully from myocarditis within a few months. Sometimes, it can take a few years for the heart to fully recover.

Some kids have lasting heart damage, but this isn’t common. If it happens, it can lead to backup of blood in the heart and lungs, arrhythmias, or cardiomyopathy (a weak, enlarged heart). If the damage is very severe, the child may need a heart transplant.

What Causes Myocarditis?

Viral infections cause most cases of myocarditis in children. It also can happen from:

  • a bacterial infection
  • an unusual reaction to a medicine or vaccine
  • eating or drinking a toxic chemical
  • an autoimmune disorder (an illness where the body attacks its own cells)
  • medicines used to treat cancer

How Is Myocarditis Diagnosed?

Doctors run tests to diagnose myocarditis, such as:

Sometimes doctors will take a small sample of the heart muscle (do a biopsy) to diagnose myocarditis. They do this with a minimally invasive procedure called cardiac catheterization.

How Is Myocarditis Treated?

A pediatric cardiologist (a doctor who treats heart problems in children) cares for kids with myocarditis. Treatment depends on the cause and how sick the child is. It can include medicines and treatments to:

  • treat the infection or autoimmune condition
  • help the heart pump more blood
  • prevent arrhythmias
  • support breathing

Some kids will need care in a pediatric or cardiac intensive care unit (PICU/CICU).

How Can Parents Help?

Over time, most children with myocarditis recover fully. Children who do have lasting heart problems may need to take medicines and/or avoid some physical activities. With the care of a cardiologist, they can find physical activity that works for them and live an active, full life.

To help your child get the best care possible:

  • Give medicines as directed by the doctor.
  • Go to all follow-up doctor visits.
  • Help your child do activities the care team told you are safe and avoid those that are risky. 

If your child has a long-term heart condition, it can feel overwhelming. But you're not alone. To find support, talk to anyone on the care team. Resources are available to help you and your child.

Medically reviewed by: Sharon M. Weinberger, MD and Dana Barry, MD
Date reviewed: January 2022