What is myocarditis?

Myocarditis is an inflammation of the heart muscle. Myocardium is the muscle of the heart, and “-itis” means inflammation.

Myocarditis occurs when a virus (or, more rarely, a bacteria or fungus) infects the body, and one of the places that it attacks is the heart. Myocarditis can also be caused by an adverse reaction to certain medicines, such as chemotherapy drugs, and exposure to some chemicals.

Some of the viruses, bacteria and fungi that can cause myocarditis are:

  • Varicella (which causes chickenpox)
  • Parvovirus B-19 (which causes fifth disease)
  • Adenovirus (which causes the common cold)
  • Streptococcus (which causes strep throat)
  • Influenza
  • Epstein-Barr virus
  • Coxsackievirus and echovirus (which can cause diarrheal illness)
  • Chlamydia
  • HIV
  • Candida (a yeast that causes the mouth infection thrush)

Myocarditis can interfere with heart function, and the heart muscle can be permanently damaged. Scar tissue may form as a result of the inflammation and interfere with heart function, plus increase the risk for abnormal heart rhythms. However, myocarditis doesn’t always cause permanent damage to the heart. Like other infections, it may resolve (clear up on its own) without the person ever being aware he or she had it.

Inflammation occurs when there is an infection because the body sends more blood to that area as part of its attempt to fight the virus, bacteria or fungus causing the infection. The heart damage caused in myocarditis probably occurs due to the direct destruction by the infectious organism as well as by the toxic response by the immune system in attempting to kill the infectious agent. Children get infections frequently, although infections of the heart occur very rarely.

Causes of myocarditis

 A diagnosis of myocarditis is alarming, and often confusing. Parents wonder: “My child had a common sickness. Why did the virus or bacteria go to the heart in this case but not in so many others?”

Doctors don’t know why viruses act differently in some people’s bodies than in others. One theory is that in some people, a particular virus might be attracted to the cells of the heart muscle because of a similarity between the proteins in the virus and the proteins in the heart muscle cells.

Another factor that varies from person to person is immune response (the body’s response to infection). Sometimes the immune response is too strong. Doctors aren’t sure why. The body fights the virus too hard, and ends up hurting its own cells. When this happens in the heart, the muscle may be permanently damaged.

Signs and symptoms of myocarditis

Because viruses and bacteria are often passed from mother to baby during birth, newborns are at a higher risk for myocarditis than other age groups. Symptoms tend to be more severe in infants, and can include:

  • Pale skin
  • Fatigue
  • Irritability
  • Difficulty breathing and eating

In older children, symptoms can include:

  • Fever
  • Rapid or labored breathing
  • Cough
  • Pale, cool hands and feet

Some children have a recognizable sickness, such as the flu or chickenpox, before symptoms of myocarditis appear. In other cases children are not noticeably sick before symptoms appear.

Older children may also experience chest pain or heart palpitations and feel unusually tired. Sometimes there are no symptoms or they are very mild.

Testing and diagnosis of myocarditis

Myocarditis is difficult to diagnose because the symptoms may be mild. They also may resemble the symptoms of many other types of illnesses.

There isn’t one definitive test that tells doctors for sure whether a patient has myocarditis. Tests for myocarditis may include:

Our pediatric cardiologists will consider your child’s symptoms and medical history and will look at X-rays and other tests to determine whether your child has myocarditis.

Taking a biopsy (a small sample) of heart tissue through cardiac catheterization can also help doctors make a more definitive diagnosis. However, because this is a procedure with some risks, our medical team may decide not to perform a catheterization.

Treatment for myocarditis

If your doctor suspects myocarditis, your child will be admitted to the hospital, in most cases to an intensive care unit.

Sometimes a medicine called intravenous immunoglobulin (IVIG) will be given through an IV line. The medicine is made from proteins extracted from human blood. (Immunoglobulin is another word for antibodies, which are blood proteins that fight infections.) Other medicines may also be used. In severe cases, mechanical pumps to take over the pumping action of the heart may be needed.

In some cases, however, the heart damage may not resolve. Additional treatment will depend on the severity of the damage. Occasionally, myocarditis results in advanced stages of heart failure, and a heart transplant is required.

Outlook for myocarditis

Many patients with myocarditis have a complete recovery, with no long-term damage to the heart. In most cases, children can maintain a good quality of life through medicines, limiting physical activity and careful monitoring of heart function.

Other patients will continue to have problems. Some will experience chronic myocarditis; this means mild inflammation persists, damage to the heart continues over a long period, and heart function may be adversely affected at some point. Other patients have decreased heart function caused by the aftermath of the myocarditis; this means the scarring and damage to the cells of the heart muscle from the original inflammation cause problems with heart function even though the inflammation and cell damage have stopped

Follow-up care for myocarditis

If your child is diagnosed with myocarditis, he will require continued care from a pediatric cardiologist.

If the myocarditis didn’t cause permanent damage, your child should visit a pediatric cardiologist once a year, or less frequently, for checkups. The doctor will monitor your child's heart function with an electrocardiogram and an echocardiogram to make sure he is healthy.

If the myocarditis did cause permanent damage, more care will be required. How much will depend on the severity of the damage. Medications may be needed to help the heart function better. In these cases, lifelong care by a cardiologist will be required.

We will help our patients transition care to an adult congenital heart disease (ACHD) specialist. The Philadelphia Adult Congenital Heart Center, a joint program of Children’s Hospital of Philadelphia and the University of Pennsylvania, meets the unique needs of adult patients.

Reviewed by Joseph Rossano, MD, MS, FAAP, FACC

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