Myocarditis in children occurs when the heart muscle becomes inflamed, typically caused by a viral infection reaching the heart.   

What is myocarditis in children?

Myocarditis is a rare occurrence in children of inflammation of the myocardium (heart muscle), which is responsible for pumping blood throughout the body.

Causes of Myocarditis in Children

Myocarditis is inflammation of the myocardium (heart muscle). It has many potential causes; however, myocarditis usually occurs when a virus, bacteria or fungus infects a child’s heart. When the heart has an infection, the body’s defense systems send more white blood cells to the infected area to fight the cause. This can cause the heart to be inflamed. As a result, scar tissue may form and interfere with the heart’s ability to function. This can increase the risk of poor heart muscle function or an abnormal heart rhythm, but it doesn’t always result in permanent damage.

The most common causes of infections leading to myocarditis are:

Viruses, such as:

• Common cold
• Influenza
• COVID-19
• Enterovirus
• Viruses causing hepatitis B and C
• Herpes simplex
• HIV
• Parvovirus
• Gastrointestinal viruses
• Rubella
• Epstein-Barr virus

Bacterial Infections, such as those that cause Lyme disease or toxic shock syndrome are another possible cause of myocarditis, though it is rare that these infections will lead to contracting it.

Parasites. While not as common, some parasites can also lead to myocarditis in children. For example, certain insects common in South and Central America can carry parasites that may result in Chagas disease, which may lead to myocarditis. Toxoplasma and Trypanosoma cruzi can also lead to inflammation of the heart.

Fungi. Children with weakened immune systems are at a higher risk of developing myocarditis due to fungi. They may be susceptible to fungal infections such as:

• Yeast infections
• Infections caused by molds
• Histoplasmosis

Other Causes of Myocarditis in Children

Other factors that can result in myocarditis:

• medications, such as chemotherapy
• exposure to carbon monoxide or radiation
• In very rare instances, diseases such as lupus, rheumatoid arthritis, ulcerative colitis and scleroderma may have a link to myocarditis.

Symptoms of Myocarditis in Children 

Newborns and Infants

Newborns are at a higher risk of getting myocarditis because their undeveloped immune systems are more susceptible to viruses and bacteria that can be passed from the mother during birth. Symptoms in newborns and infants can include:

• Fever
• Listlessness
• Difficulty eating and breathing
• Irritability and fussiness
• Cool hands and feet due to poor circulation
• Pale skin
• Fatigue and sleeping more
• Less urine output because their kidneys aren’t functioning properly

Symptoms are generally more severe in infants than in older children.

Older Children

Symptoms of myocarditis are slightly different in children over the age of 2. They may include the symptoms above, but older children may also experience:

• Belly pain
• Nausea
• Cough
• Chest pains
• Heart palpitations
• Shortness of breath
• Fainting
• Swelling in the legs, feet or face
• Fatigue
• Inability to tolerate exercise

Diagnosis of Myocarditis in Children

It can be difficult to diagnose myocarditis in children because their symptoms may be mild or resemble the symptoms of other illnesses, such as the flu or the common cold. In addition, there are no definitive tests to determine whether a child has myocarditis. However, a variety of tests may indicate myocarditis, such as:

• Electrocardiogram (evaluation of heart rhythm)
• Echocardiogram (ultrasound of heart structure and function)
• Chest X-ray
• Cardiac MRI
• Cardiac catheterization
• Blood tests

Treatment for Myocarditis in Children

Although the inflammation of the heart usually goes away on its own, treatment is often needed to help the function of the heart during the inflammation.

Children with myocarditis are generally admitted to the hospital’s pediatric intensive care unit (PICU) or cardiovascular intensive care unit (CVICU) for care. Treatment depends on the cause of the myocarditis. Often, a specific cause of myocarditis cannot be found, in which case it is called “idiopathic myocarditis.” In the PICU, treatment can include:

• Antibiotics to fight infection
• Anti-inflammatory medicines (steroids) to control inflammation
• Intravenous immunoglobulin (IVIG), a medicine that helps control the inflammatory process
• Medication to treat symptoms of heart failure or abnormal heart rhythms
• Diuretics to help clear excess fluid from the body tissue
• In severe cases, a mechanical support pump to aid the heart’s ability to pump

Long-Term Outlook of Myocarditis in Children

With the right medical treatment, most children with myocarditis either have complete recovery or improvement in heart function, which occurs within two or three months of the onset of symptoms. Children with myocarditis will need to have ongoing follow-up care with their pediatric cardiologist.

If untreated, there is a higher risk of children developing long-term heart disease. Other potential complications may include:

• Dilated cardiomyopathy
• Heart arrhythmias
• Heart attack
• Stroke
• Heart failure

In some instances, children can develop progressive heart failure. In such cases, the child may require a heart transplant.

There is a more serious risk of heart failure for newborns with myocarditis. Some infants may need an urgent heart transplant.