Myocarditis
Medically reviewed by Drugs.com. Last updated on May 28, 2025.
What is myocarditis?
Myocarditis is an inflammation of the heart muscle that may decrease the ability of the heart to pump blood normally. It can be caused by:
- An infection: Many infections have been associated with myocarditis. Some of the more likely germs include:
- Viral infections: Many different viruses can cause myocarditis. Examples include adenovirus, coxsackievirus, Epstein-Barr virus, HIV, varicella (chickenpox), human herpes virus 6, and SARS CoV-2 (COVID-19). Often the person has no preceding symptoms of a cold, cough, nasal congestion, or rash and only becomes aware of the infection when heart failure occurs. Viral infections are among the most common causes of myocarditis.
- Bacteria: Rarely, myocarditis is a complication of endocarditis, an infection of the heart valves and the lining inside the heart's chambers caused by bacteria. In some people with diphtheria, a toxin (poison) produced by C. diphtheriae bacteria causes a form of myocarditis that leads to a flabby, stretched-out heart muscle. Because the damaged heart cannot pump blood efficiently, severe heart failure may develop within the first week of illness.
- Chagas' disease: This infection, caused by the protozoan Trypanosoma cruzi, is transmitted by an insect bite. In the United States, myocarditis caused by Chagas' disease is most common among travelers to or immigrants from Central and South America. In up to a third of people with Chagas' disease, a form of chronic (long-term) myocarditis develops years after the first infection. This chronic myocarditis leads to significant destruction of heart muscle with progressive heart failure.
- Lyme myocarditis: Lyme disease, an infection caused by the tick-borne bacterium Borrelia burgdorferi, can cause myocarditis or other heart problems.
- Toxic substances and certain drugs: Myocarditis also can be caused by:
- overuse of alcohol
- radiation
- chemicals (hydrocarbons and arsenic)
- medicines such as doxorubicin (Adriamycin, a type of chemotherapy) and clozapine (Clorazil, a drug that treats psychosis); very rarely, vaccinations, including those for SARS-CoV-2 and smallpox, may cause myocarditis
- Inflammatory diseases: This includes systemic lupus erythematosus (SLE or lupus) and other autoimmune diseases, and sarcoidosis.
Symptoms of myocarditis
The symptoms of myocarditis depend on the cause and severity. For example, many people with uncomplicated myocarditis caused by coxsackievirus don't have any symptoms. Other people have fever, chest pain, cardiac arrhythmias (abnormally fast, slow, or irregular heartbeats), sudden loss of consciousness (syncope), or symptoms related to heart failure (shortness of breath, leg swelling).
Diagnosing myocarditis
Your doctor may suspect myocarditis based on your medical history and symptoms. To confirm the diagnosis, your doctor will examine you, paying special attention to your heart. This will be followed by an EKG (a test that measures the heart's electrical activity), a chest x-ray, an echocardiogram (a test using sound waves to assess heart function), and blood tests.
In some patients, your doctor may order tests to determine if a virus or other infectious agent is the cause. These tests may include blood tests or attempts to detect certain types of viruses from stool, throat washings, or other body fluids.
Expected duration of myocarditis
How long myocarditis lasts depends on the cause and the person's general health before the heart problems began. For example, in many healthy adults with uncomplicated coxsackievirus myocarditis, symptoms can start to improve over a couple of weeks; in other cases, the heart takes a few months to recover. Sometimes, the damage to the heart muscle is permanent, and heart failure persists even after the inflammation has resolved.
Preventing myocarditis
Myocarditis caused by certain infections can often be avoided by vaccination and by practicing good hygiene, especially washing your hands often. HIV can be prevented by following safe sex practices and avoiding intravenous drug use. Myocarditis caused by insect-borne Chagas' disease can be prevented by using effective insecticides in Latin American countries where the illness is common.
Treating myocarditis
Treatment of myocarditis depends on the cause and severity. For example, people with only mild viral myocarditis may recover completely with only a period of rest. They will be advised not to smoke or to drink alcohol, and to limit strenuous activities.
People with myocarditis that causes heart failure symptoms or irregular heartbeat (cardiac arrhythmias) will be treated in a hospital. There they may receive one or more of the following:
- oxygen delivered through nasal prongs
- medication or a pacemaker to treat an irregular heartbeat (arrhythmia)
- medication, including ACE inhibitors, beta blockers, diuretics, and vasodilators, to treat heart failure
- pain relievers, if needed, for chest pain (though nonsteroidal anti-inflammatory drugs such as ibuprofen should be avoided)
- antibiotics to treat bacterial myocarditis or Lyme disease
- diphtheria antitoxin and antibiotics to treat diphtheria myocarditis
- glucocorticoid or other anti-inflammatory and immunosuppressive medicines to treat autoimmune diseases and sarcoidosis
- heart transplant (for severe myocarditis that damages heart function and does not improve with other measures).
When to all a professional
Call your doctor immediately if you have chest pain, even if you think that you are too young to have heart problems (as people of any age can get myocarditis).
Prognosis
In many people with uncomplicated viral myocarditis, the heart muscle improves without specific therapy, and myocarditis-related EKG and echocardiogram abnormalities eventually disappear. However, more severe forms of myocarditis may cause permanent damage to the heart muscle, leading to long-term heart failure and significant abnormalities of heart rhythm.
Additional info
National Heart, Lung, and Blood Institute (NHLBI)
https://www.nhlbi.nih.gov/
Further information
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.