What is myocarditis?

Myocarditis refers to an inflammation of the heart that usually results from an infection within the heart muscle itself. It is most often caused by a virus but can be caused by some bacteria (including the bacteria that causes Lyme Disease), fungi, autoimmune disorders like SLE (Systemic Lupus Erythematosis), and a host of medical drugs.

The normal heart is a four-chamber pump. The heart walls are made of muscle cells that respond to the heart’s electrical impulse by briskly contracting (shortening). Myocarditis causes swelling and damage of the heart muscle cells and thus impairs their ability to contract. If the damage is mild, the heart has enough reserve so that no symptoms occur. If severe, the heart is unable to pump enough blood to meet the body’s needs and symptoms of congestive heart failure occur.

The heart rhythm is under the control of the heart’s electrical system. Cell damage caused by myocarditis can be a source of abnormal heart rhythms including heart block, ventricular tachycardia, and/or ventricular fibrillation.

What are the effects of this problem on my child's health?

The health effects of myocarditis vary widely and depend on the degree of the muscle damage. If mild, there may be no symptoms or only symptoms with exercise. If the heart is unable to pump enough blood to meet the body’s needs, symptoms of congestive heart failure will occur. Myocarditis can also be associated with abnormal heart rhythms including atrial flutter, atrial fibrillation, heart block, and ventricular tachycardia.

If symptoms occur, these can resolve, remain stable, or worsen over time to the degree that a heart transplant is needed.

How is this problem diagnosed?

Symptoms: Possible symptoms include palpitations (heart racing or "skipping" heart beats), low energy levels, and low exercise tolerance. Symptoms of congestive heart failure also include rapid breathing, clammy sweating, poor appetite, poor weight gain in young children, and swelling around the eyes, hand, and feet (more common in older children and young adults).

Physical findings: The exam depends on the degree of heart damage. If the heart is only mildly affected, the exam may be normal. If there is congestive heart failure, the heart rate and breathing rate are often fast. There may be a heart murmur (sound made by abnormal backward flow through the mitral valve) or other extra heart sounds, and the liver may be enlarged.

Medical tests: An echocardiogram is one of the first tests done and provides useful data about the severity of the problem. The diagnosis may be confirmed by a heart biopsy done during heart catheterization. If an infection is felt to be the cause of the myocarditis, blood cultures or other special blood tests may be help identify the causative organism. Other heart tests include an electrocardiogram (ECG), Holter monitor, and chest x-ray.

How is the problem treated?

The mainstay of treatment is rest. Heart medicines such as digoxin, lasix, aldactone and captopril or enalapril are used to treat symptoms of congestive heart failure. If the cause is bacterial, antibiotics are used. A short course of steroids or other drugs that decrease the immune response may be used if the usual treatment is not helpful or if heart block occurs. Long-term therapy depends on the degree of residual heart damage and the presence of abnormal heart rhythms.

What are the long-term health issues for these children?

The long-term outlook depends largely on the degree of residual heart damage. In about one third of children, the problem resolves completely within about 6 months. In one third, the problem remains stable, and in one-third the symptoms progress and more intensive treatment is needed. If there is severe heart damage that does not respond to treatment, a heart transplant may be needed.

SBE prophylaxis: Children with myocarditis are at increased risk for subacute bacterial endocarditis (SBE) if valve leakage occurs. SBE is an infection of the heart caused by bacteria in the blood stream. Children with heart valve leakage are more prone to this problem because of the altered flow of blood through the heart. SBE can occur after dental work and some other medical procedures because they almost always result in bacteria entering the blood. SBE can usually be prevented by taking an antibiotic before these procedures.

Exercise guidelines: An individual exercise program is best planned with the doctor so that all factors can be included. Rest is needed during the initial phases of myocarditis. Afterwards, exercise guidelines are based on the degree of residual heart damage.


Gajarski RJ & Towbin J. Recent advances in the etiology, diagnosis, and treatment of myocarditis and cardiomyopathies in children. Curr Opinion Pediatrics 1995;7:587-594.

Written by: S. LeRoy RN, MSN, CPNP

Reviewed September, 2012