Pediatric myocarditis is inflammation of the heart muscle in an infant or young child.
Causes, incidence, and risk factors
Myocarditis is rare in young children. It is slightly more common in older children and adults. It tends to be more severe in newborns and young infants than in children over age 2.
In children it is usually caused by viruses that reach the heart, such as the influenza (flu) virus, Coxsackie virus, parovirus, and adenovirus. However, it may also be caused by bacterial infections, including Lyme disease.
Other causes of pediatric myocarditis include:
- Allergic reactions to certain medications
- Exposure to certain chemicals in the environment
- Infections due to fungus or parasites
- Some diseases (autoimmune disorders) that cause inflammation throughout the body
- Some drugs
The heart may be directly damaged by the virus or the bacteria that infect it. The body’s own response to an infection can also damage the heart muscle (called the myocardium).
When you have an infection, your body’s immune system produces special cells to fight off disease. If the infection affects your myocardium, the disease-fighting cells enter the heart.
While trying to get rid of the infection, the immune cells may also damage the heart muscle, causing it to become inflamed and swollen. This leads to symptoms of heart failure. In addition, the virus or bacteria may damage the heart muscle.
Symptoms may be mild at first and hard to detect. However, in newborns and infants, symptoms may sometimes appear suddenly. They may include symptoms of heart failure:
- Failure to thrive or poor weight gain
- Feeding difficulties
- Fever and other symptoms of infection
- Low urine output (a sign of decreasing kidney function)
- Pale, cool 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
- Swelling (edema) in the legs, feet, and face
Signs and tests
Pediatric myocarditis can be hard to diagnose because the signs and symptoms often mimic those of other heart and lung diseases, or a bad case of the flu.
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 and rashes.
A chest x-ray can show enlargement (swelling) of the heart. If the health care provider suspects myocarditis based on the exam and chest x-ray, an electrocardiogram may also be done to help make the diagnosis.
Further tests may include:
- Blood cultures to check for infection
- Blood tests to look for antibodies against viruses or the heart muscle itself
- Blood tests to check liver and kidney function
- Complete blood count
- Heart biopsy (the most accurate way to confirm the diagnosis, but not always needed)
- Special tests to check for the presence of viruses in the blood (viral PCR)
There is no cure for myocarditis. The heart muscle inflammation usually goes away on its own in time.
The goal of treatment is to support heart function until the inflammation goes away. Many children with this condition are admitted to a hospital. Because activity can strain the heart, it is often limited while the heart is inflamed.
Treatment may include:
- Antibiotics to fight bacterial infection
- Anti-inflammatory medicines called steroids to control inflammation
- Intravenous immunoglobulin (IVIG), a medicine made of substances (called antibodies) that the body produces to fight infection, to control the inflammatory process
- Mechanical support using a machine to help the heart function (in extreme cases)
- Medicines to treat symptoms of heart failure
- Medicines to treat abnormal heart rhythms
How the child recovers from myocarditis 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, damage to the heart muscle is so severe that a heart transplant is needed.
- Enlargement of the heart that leads to reduced heart function (dilated cardiomyopathy)
- Heart failure
- Heart rhythm problems
Calling your health care provider
Make an appointment with your child’s pediatrician if signs or symptoms of this condition occur.
There is no known prevention. However, prompt testing and treatment may reduce the disease risk.