Myocarditis is an uncommon disorder. Most of the time, it is caused by an infection that reaches the heart.
When you have an infection, your immune system produces special cells to fight off disease. If the infection affects your heart, the disease-fighting cells enter the heart. However, the chemicals made by these cells can also damage the heart muscle. As a result, the heart can become thick, swollen, and weak.
Many cases are caused by a virus that reaches the heart. These can include the influenza (flu) virus, coxsackievirus, parovirus, cytomegalovirus, adenovirus, and others.
It may also be caused by bacterial infections such as Lyme disease, streptococcus, mycoplasma, and chlamydia.
Other causes of myocarditis include:
- Reactions to certain medicines, such as certain chemotherapy drugs
- Exposure to chemicals in the environment, such as heavy metals
- Infections due to fungus or parasites
- Autoimmune disorders that cause inflammation throughout the body
Sometimes the exact cause may not be discovered.
Myocarditis is inflammation of the heart muscle.
The condition is called pediatric myocarditis when it occurs in children.
Exams and Tests
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 health care provider may hear a rapid heartbeat or abnormal heart sounds while listening to the child's chest with a stethoscope. A physical exam 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 provider suspects myocarditis based on the exam and chest x-ray, an electrocardiogram may also be done to help make the diagnosis. Heart biopsy is the most accurate way to confirm the diagnosis, but it is not always needed, Also, a heart biopsy may not reveal the diagnosis if the small piece of heart tissue that is removed does not contain the suspected organism or other indicators.
Other tests that may be needed 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
- Special tests to check for the presence of viruses in the blood (viral PCR)
The outcome can vary, depending on the cause of the problem and a person’s overall health. Some people may recover completely. Others may have lasting heart failure.
Treat conditions that cause myocarditis promptly to reduce the risk.
There may be no symptoms. Symptoms may be similar to the flu. If symptoms occur, they may include:
- Chest pain that may resemble a heart attack
- Fatigue or listlessness
- Fever and other signs of infection including headache, muscle aches, sore throat, diarrhea, or rashes
- Joint pain or swelling
- Leg swelling
- Pale, cool hands and feet (a sign of poor circulation)
- Rapid breathing
- Rapid heart rate
Other symptoms that may occur with this disease:
Treatment is aimed at the cause of the problem, and may involve:
- Antibiotics to fight bacterial infection
- Medicines called steroids to reduce swelling
- Intravenous immunoglobulin (IVIG), a medicine made of substances (called antibodies) that the body produces to fight infection, to control the inflammatory process
- Diuretics to remove excess water from the body
- Low-salt diet
- Reduced activity
If the heart muscle is weak, your provider will prescribe medicines to treat heart failure. Abnormal heart rhythms may require the use of other medicines. You may also need a device such as a pacemaker, or implantable cardioverter-defibrillator's to correct a dangerous abnormal heartbeat. If a blood clot is in the heart chamber, you will also receive blood thinning medicine.
Rarely, a heart transplant may be needed if the heart muscle has become too weak to function.
When to Contact a Medical Professional
Cooper LT, Knowlton KU. Myocarditis. In: Zipes DP, Libby P, Bonow RO, Mann DL, Tomaselli GF, Braunwald E, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 11th ed. Philadelphia, PA: Elsevier; 2019:chap 79.
Knowlton KU, Narezkina A, Savoia MC, Oxman MN. Myocarditis and pericarditis. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, Updated Edition. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 86.
McKenna WJ, Elliott P. Diseases of the myocardium and endocardium. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 60.