What is myocarditis?

The myocardium is the muscle of the heart and “-itis” means inflammation. Myocarditis is an inflammation of the heart muscle.

Myocarditis is when a virus (or, more rarely, a bacteria or fungus) infects the body and attacks the heart. Inflammation occurs when there is an infection because the body sends more infection-fighting blood cells to that area as part of its attempt to fight the virus, bacteria or fungus causing the infection. Although children get infections often, infections of the heart are rare.

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)
• COVID
• Enterovirus 

Myocarditis can also be caused by a negative reaction to certain medicines (such as chemotherapy drugs) and exposure to some chemicals.

Myocarditis can interfere with heart function, and the heart muscle can be permanently damaged. Scar tissue may form because of the inflammation, and this can increase the risk for abnormal heart rhythms. However, myocarditis doesn’t always cause permanent damage to the heart. Like other infections, it may clear up on its own without the person ever being aware they had it.

Causes of myocarditis in children

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 the body’s response to an infection (immune response). Sometimes the immune response is too strong. When this happens, 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 in children

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
• Decreased appetite
• Chest pain or heart palpitations
• Fatigue 

Some children have a recognizable sickness, such as the flu or chickenpox, before symptoms of myocarditis appear. In other cases, children don’t seem sick at all before symptoms appear. Sometimes symptoms are mild.

Testing and diagnosis of myocarditis

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

There isn’t one specific test that can determine for sure whether a child has myocarditis. Instead, your doctor will make a diagnosis based on the results of many tests, which may include: 

• Chest x-ray
• Echocardiogram (also called echo or ultrasound), which is when sound waves create an image of the heart
• Electrocardiogram (ECG or EKG), which is a record of the electrical activity of the heart
• Cardiac magnetic resonance imaging (MRI), which is a 3-D image that shows the heart’s structures in detail
• Cardiac catheterization, which is when a thin tube is inserted into the heart through a vein and/or artery in the leg to provide detailed information about the structure and function of the heart

Your pediatric cardiologist will also consider your child’s symptoms and medical history. They may need to take a small sample of heart tissue (called a biopsy) through cardiac catheterization to make a more definitive diagnosis.  

Treatment for myocarditis in children

If your doctor suspects myocarditis, your child will be admitted to the hospital, often to a cardiac intensive care unit (CICU).

Your child may receive medication to support the heart through the course of the infection. Some of these medications may be given through an IV (intravenous line). 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.

Ventricular assist devices 

In severe cases, a mechanical pump can be used to take over the pumping action of the heart if it isn’t working properly. This pump is called a ventricular assist device (VAD). A VAD pumps blood from the heart’s pumping chamber (ventricle) to the body by way of the aorta, the biggest artery in the body. Sometimes these devices can stay in for months or even years and can be used as a bridge to recovery of heart function or as a bridge to heart transplant. 

Outlook for myocarditis

Many children 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 medication, limited physical activity and carefully monitoring heart function. 

Some children will have ongoing issues. Some may develop chronic myocarditis, where mild inflammation and heart damage continue over time, affecting heart function. Others may have reduced heart function due to scarring from the original inflammation, even after the inflammation has stopped.

Follow-up care for myocarditis

If your child is diagnosed with myocarditis, they 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 for checkups. The cardiologist will monitor your child's heart function with an electrocardiogram and an echocardiogram to make sure their heart is healthy. 

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

At Children’s Hospital of Philadelphia (CHOP), our pediatric cardiologists follow patients until they are young adults. The Philadelphia Adult Congenital Heart Center, a joint program of CHOP and Penn Medicine, meets the unique needs of adults who were born with heart defects. 

At CHOP’s Cardiac Center, we support our adolescent and young adult patients through a smooth and seamless transition to adult cardiology care at the Philadelphia Adult Congenital Heart Center or, if desired, to a cardiologist with congenital heart disease expertise in another location.