Myocarditis in Children EMPIRE STATE LYME DISEASE ASSOCIATION, INC.

Myocarditis is an inflammation of the myocardium, the thick muscular layer making up the major portion of your heart. When this condition is uncommon in children, it can cause pumping action of your child's heart to weaken. This in turn makes the heart unable to supply the rest of your body with enough oxygen-rich blood. Clots can form as well, potentially leading to a stroke or heart attack. There are many causes of myocarditis including infections, medications, chemicals, radiation, and certain diseases that cause inflammation in many different organs of the body. In most children, myocarditis is most often triggered by an infection, usually viral, involving the heart.

What causes Myocarditis in children?

Years ago, rheumatic fever was a common cause of myocarditis. But today, there are usually other reasons for myocarditis, most often when it develops secondary to an underlying infection caused by:

Viruses. The virus most often associated with myocarditis is coxsackievirus B. But adenovirus, parvovirus B19, echovirus, influenza virus, Epstein-Barr virus and rubella virus are other viral causes of myocarditis. HIV, the virus that causes AIDS, can directly infiltrate the heart muscle.
Bacteria. These include Staphylococcus aureus, which can also cause an infection of the heart valves called endocarditis.and a tick-borne bacterium called Borrelia burgdorferi, which is responsible for Lyme disease. Rarely, bacteria such as those causing the tick-borne illness Lyme disease can cause myocarditis. It is important to recognize that even though a child may have develop Lyme Disease it is rare for them to develop myocarditis. Myocarditis also occurs in more than one-fourth of all people with diphtheria, a disease caused by the bacterium Corynebacterium diphtheriae.
Parasites. Among these are such parasites as Trypanosoma cruzi and toxoplasma, including some that are transmitted by insects and can cause a condition called Chagas' disease. This disease is much more prevalent in Central and South America than in the United States, but it can occur in travelers to and in immigrants from that part of the world.
Fungi. These causes include candida, aspergillus and histoplasma. They are rare causes of myocarditis.

When an infectious organism is the cause of the myocarditis, the initial event that must occur is infection of the heart by that organism. The child's immune system is then called upon to eliminate the infection. In some children, this response is over-aggressive so that in addition to destroying the infecting organism, the heart cells themselves may be damaged.

Most of the damage to the heart seen is a result of the body's immune reaction to the infectious organism, not the organism itself. It is unclear why this happens in some children. The abnormal immune response may be confined to a small area or involve a large portion of muscle tissue. The severity of symptoms is often related to how much heart muscle is involved.

Damaged muscle cells may heal over time or there may be cell death followed by scar formation. If this process is extensive and a large portion of the heart is involved, the ability of the heart to pump blood is impaired. . There is thickening and swelling of the heart muscle. All four chambers of the heart may be affected and become enlarged. As a result, the important organs and tissues in the body are deprived of oxygen and nutrients and cannot eliminate waste products. This is often referred to as congestive heart failure.

Myocarditis also sometimes occurs when a child is exposed to:

Certain chemicals. These may include substances such as arsenic and hydrocarbons.
Medications that may cause an allergic or toxic reaction. These include antibiotics such as penicillin and streptomycin and anti-epilepsy drugs such as phenytoin and carbamazepine, as well as some illegal substances, such as cocaine.
Systemic diseases. These include lupus, other connective tissue disorders, inflammation of blood vessels (vasculitis), and rare inflammatory conditions such as Wegener's granulomatosis.

Symptoms of myocarditis

The signs and symptoms of myocarditis may vary, depending on the cause and the severity of the disease. The symptoms of myocarditis are usually subtle, making the diagnosis difficult, or the child may experience overt symptoms of heart failure. Clinical experience has shown the severity of symptoms or illness is dependent upon the age of the child. Children over 2 years of age may be less symptomatic than newborns and infants who are usually more severely affected. This is thought to be due to the immaturity of a baby's immune system.

The most common signs and symptoms include:

Vague chest pains
A rapid or abnormal heartbeat (arrhythmia)
Shortness of breath, particularly during physical activity, or complaints of palpitations (skipped or missed heart beats)
Fluid retention with swelling of your child's legs, ankles and feet
Joint pain
Fever
Fatigue
High temperature
Loss of appetite
Breathing difficulties
Bluish or grayish discoloration of the skin

Other signs and symptoms may occasionally occur as well, such as:

Fainting or a sudden loss of consciousness, which may be associated with irregular heart rhythms
A decline in the volume urine
Other symptoms associated with a viral infection, such as a headache, body aches, a fever and a sore throat

Diagnosis of myocarditis

Unfortunately, to the frustration of parents and doctors, there is no specific test for myocarditis. It is mostly a clinical diagnosis; therefore the physician must rely on the history provided by the family and physical examination of the child.

There are many tests that can be performed that help support a suspected diagnosis of myocarditis. The most common test is a chest X-ray. Often the heart size is enlarged, the blood vessels of the lungs are prominent, and fluid may enter the lungs.

An electrocardiogram can also give helpful clues if the diagnosis is suspected; however, the findings may be non-specific.

An echocardiogram or heart ultrasound can be used to assess heart size and overall function which helps confirm the clinical diagnosis as well as rule out the presence of blood clots within the heart chambers which can form due to poor heart function.

Blood tests measure white and red blood counts, as well as levels of certain enzymes that indicate damage to your heart muscle. Blood tests can also detect antibodies against viruses and other organisms that may indicate a myocarditis-related infection.

The most precise way to make the diagnosis of myocarditis relies on heart biopsy obtained during a cardiac catheterization. This involves the use of a long catheter that is passed up a large blood vessel in the leg. Once the catheter is in the heart, a tiny piece of heart muscle is obtained and sent to the pathologist for inspection under the microscope. Results vary but the diagnosis of myocarditis is made by this method up to 65 percent of the time. The results of the biopsy are not 100 percent because the areas of the heart affected by the inflammation are often patchy and may be missed.

Treatment of myocarditis

The inflammation that occurs will usually resolve on its own. There is no cure for myocarditis. In general, the goal of medical therapy is to support the heart function so that adequate blood circulation is maintained.

Medications that are able to help the heart work more either by regulating the blood pressure or by improving the ability of the heart to pump blood are the first line of treatment. One or more of these medications may be considered depending upon the severity of the myocarditis. In addition, a diuretic is commonly used to help clear excess fluid from the lungs or other body tissues. There are also medications that are designed to decrease the abnormal immune response, which are currently under investigation. One drug frequently used is called intravenous immunoglobulin (IVIG) which consists of purified antibodies, the substances that the body's immune cells produce to fight infection. Its mechanism of action is unclear but it has been shown to slow down the inflammatory process.

Most children diagnosed with myocarditis are admitted to an intensive care unit for initial management. It is important for the child to be placed on bed rest. There is evidence to suggest that strenuous activity may be harmful to the heart during the recovery period.

Depending upon the severity of the myocarditis, this may mean that physical activity is restricted for weeks to months. The child's physical activity should be slowly increased over time.

The good news is that approximately two-thirds of the children, with appropriate medical management, will have a complete recovery. If untreated, only 10 to 20 percent will have a spontaneous recovery and 80 percent will develop chronic heart disease. For most children, recovery usually occurs within 2-3 months from the onset of the illness. Of the remaining one-third, 10 to 20 percent will improve but have chronic residual heart problems called "dilated cardiomyopathy."

This is a condition where the heart has become enlarged and may have diminished function or residual heart failure. In this case, the child will require long term follow-up by a cardiologist Other children may experience problems with the electrical conduction system within the heart and are at risk for rhythm problems. A common rhythm disturbance in this group is called heart block. In its most severe form, heart block may result in a slow heart rhythm that requires placement of a pacemaker. Other irregular heart rhythms may also occur but are often effectively treated with medications. The remaining 10 percent will develop rapidly progressive disease with severe heart failure.

The population that is at the highest risk for serious disease is newborns. The mortality rate is as high as 50 to 70 percent. When this is the case, there is a high risk of sudden death and some children may need a heart transplant urgently. This severity of disease is rare and therefore represents a very small number of children.

adapted from the web site of the Cincinnati Children's Heat Center and posted 07-07-05 on kidsgrowth.com

This information should not be relied on as medical advice and is not intended to replace the advice of your child’s doctor. Please read our full disclaimer.