Pediatric myocarditis is inflammation and weakness of the heart muscle in an infant or young child.

Myocarditis is an uncommon disorder. In children it is usually caused by viral infections that reach the heart, such as the influenza (flu) virus, Coxsackie virus, and adenovirus. However, it may also occur during or after other viral or bacterial infections such as polio, rubella, Lyme disease, and others.

When you have an infection, your body's immune system produces special cells that release certain chemicals to fight off disease. If the infection affects your heart, the disease-fighting cells enter the heart. However, the chemicals they produce can damage the heart muscle, causing it to become thick and swollen. This leads to symptoms of heart failure. In addition, the virus or bacteria damage the heart muscle.

Other causes of pediatric myocarditis may include:

• Allergic reactions to certain medications
• Being around certain chemicals
• Certain diseases (autoimmune disorders) that cause inflammation throughout the body
• Certain drugs
• Infections due to fungus or parasites
• Radiation

Pediatric myocarditis tends to be more severe in newborns and young infants than in children over age 2.

Symptoms may be mild at first and difficult to detect.

In newborns and infants, symptoms may sometimes appear suddenly and may include:

• Anxiousness
• Failure to thrive
• Feeding difficulties
• Fever and other symptoms of infection
• Heart failure
• Listlessness
• Low urine output (a sign of decreasing kidney function)
• Pale hands and feet (a sign of poor circulation)
• Rapid breathing
• Rapid heart rate

Symptoms in children over age 2 may also include:

• Belly area pain and nausea
• Chest pain
• Cough
• Fatigue
• Swelling (edema) in the legs, feet, and face

Pediatric myocarditis can be difficult to diagnose because the signs and symptoms often mimic those associated with other heart and lung diseases.

The doctor may hear a rapid heartbeat or abnormal heart sounds while listening to the child’s chest with a stethoscope. A physical examination may detect fluid in the lungs and swelling in the legs in older children.

There may be signs of infection, including fever, rashes, red throat, itchy eyes, and swollen joints.

A chest x-ray can show enlargement (swelling) of the heart. An electrocardiogram and echocardiogram should also be done.

Further tests may include:

• Blood cultures to check for infection
• Blood tests to look for antibodies against the heart muscle and the body itself
• Blood tests to check liver and kidney function
• Complete blood count
• Heart biopsy (the most accurate way to confirm the diagnosis)

There is no cure for myocarditis, although the heart muscle inflammation usually goes away on its own in time.

The goal of treatment is to support heart function and treat the underlying cause of the myocarditis. Most children with this condition are admitted to a hospital. Activity can strain the heart and therefore is often limited.

Treatment may include:

• Antibiotics to fight infection
• Anti-inflammatory medicines called steroids to control inflammation
• Intravenous immunoglobulin (IVIG), a medicine made of the substances that your body produces to fight infection, to control the inflammatory process
• Medicines called diuretics to remove excess water from the body
• Medicines to treat heart failure and abnormal heart rhythms

How well the child does depends on the cause and his or her overall health. With appropriate treatment, most children recover completely. However, some may have permanent heart disease. Newborns have the highest risk for serious disease and complications (including death) due to myocarditis. In rare cases, an urgent heart transplant is necessary.

• Enlargement of the heart that leads to reduced heart function (dilated cardiomyopathy)
• Heart failure
• Heart rhythm problems

Make an appointment with your child's pediatrician if signs or symptoms of this condition occur.

There is no known prevention. However, prompt and adequate treatment of viral, bacterial, or parasitic diseases may help reduce your child's risk.

Freedman SB, Haladyn JK, Floh A, Kirsh JA, Taylor G, Thull-Freedman J. Pediatric myocarditis: emergency department clinical findings and diagnostic evaluation. Pediatrics. 2007 Dec;120(6):1278-85.

Behrman RE. Nelson Textbook of Pediatrics. 17th ed. Philadelphia, Pa: WB Saunders; 2004.

Park MK, Troxler RG. Pediatric Cardiology for Practitioners. 4th ed. St. Louis, Mo: Mosby, Inc; 2002.

Schwartz SM, Wessel DL. Medical cardiovascular support in acute viral myocarditis in children. Guidelines for the Treatment of Myocarditis in Infants and Children and Proceedings of the 2005 Pediatric Cardiac Intensive Care Symposium. Pediatr Crit Care Med. 7(6) Supplement:S12-S16, November 2006.