Myocarditis is inflammation of the heart muscle (myocardium). The inflammation can reduce the heart's ability to pump blood. Myocarditis can cause chest pain, shortness of breath, and rapid or irregular heart rhythms (arrhythmias).
Infection with a virus is one cause of myocarditis. Sometimes a drug reaction or general inflammatory condition causes myocarditis.
Severe myocarditis weakens the heart so that the rest of the body doesn't get enough blood. Clots can form in the heart, leading to a stroke or heart attack.
Treatment for myocarditis may include medications, procedures or surgeries.
Some people with early myocarditis don't have symptoms. Others have mild symptoms.
Common myocarditis symptoms include:
- Chest pain
- Swelling of the legs, ankles and feet
- Rapid or irregular heartbeat (arrhythmias)
- Shortness of breath, at rest or during activity
- Light-headedness or feeling like you might faint
- Flu-like symptoms such as headache, body aches, joint pain, fever or sore throat
Sometimes, myocarditis symptoms are like a heart attack. If you are having unexplained chest pain and shortness of breath, seek emergency medical help.
Myocarditis in children
When children develop myocarditis, symptoms may include:
- Breathing difficulties
- Chest pain
- Rapid breathing
- Rapid or irregular heart rhythms (arrhythmias)
When to see a doctor
Contact your health care provider if you have symptoms of myocarditis. Symptoms of myocarditis can seem like a heart attack. Get emergency medical help if you have unexplained chest pain, rapid heartbeats or shortness of breath.
If you have severe symptoms, go to the emergency room or call for emergency medical help.
Myocarditis may be caused by infections, some drugs and chemicals, or a condition that causes body-wide inflammation. Often, the cause of myocarditis isn't found.
Potential causes of myocarditis include:
Viruses. Many viruses have been linked to myocarditis, including those that cause the common cold (adenovirus); COVID-19; hepatitis B and C; parvovirus, which causes a mild rash, usually in children (fifth disease); and herpes simplex virus.
Gastrointestinal infections (echoviruses), mononucleosis (Epstein-Barr virus) and German measles (rubella) also can cause myocarditis. Myocarditis can also be caused by HIV, the virus that causes AIDS.
- Bacteria. Bacteria that can cause myocarditis include staphylococcus, streptococcus, and bacteria that cause diphtheria and Lyme disease.
- Parasites. Among these are Trypanosoma cruzi and toxoplasma. Some parasites are transmitted by insects and can cause a condition called Chagas disease. Chagas disease is much more common in Central and South America than in the United States.
- Fungi. A fungal infection may cause myocarditis, particularly in people with weakened immune systems. Those linked to myocarditis include yeast infections, such as candida; molds, such as aspergillus; and histoplasma, often found in bird droppings.
Myocarditis may also be caused by:
- Certain medications or illegal drugs (drug-induced myocarditis). These include drugs used to treat cancer; antibiotics, such as penicillin and sulfonamide drugs; some anti-seizure medications; and cocaine.
- Chemicals or radiation. Exposure to carbon monoxide and radiation can sometimes cause heart muscle inflammation.
- Other inflammatory diseases. Conditions that may cause myocarditis include lupus, Wegener's granulomatosis, giant cell arteritis and Takayasu's arteritis.
Usually, myocarditis goes away without permanent complications. However, severe myocarditis can permanently damage the heart muscle.
Potential complications of myocarditis may include:
- Heart failure. Untreated, myocarditis can damage the heart muscle so that it can't pump blood well. In severe cases, myocarditis-related heart failure may require a ventricular assist device or a heart transplant.
- Heart attack or stroke. If the heart muscle is injured and can't pump blood, the blood that collects in the heart can form clots. A heart attack can occur if a clot blocks one of the heart (coronary) arteries. A stroke can occur if a blood clot in the heart travels to an artery leading to the brain.
- Rapid or irregular heart rhythms (arrhythmias). Damage to the heart muscle can change how the heart beats. Certain arrhythmias increase the risk of stroke.
- Sudden cardiac death. Certain serious arrhythmias can cause the heart to stop beating (sudden cardiac arrest). It's deadly if not treated immediately (sudden cardiac death).
There's no specific prevention for myocarditis. However, taking these steps to prevent infections might help:
- Avoid close contact with people who are sick. Stay away from people with symptoms of the flu or other respiratory illness until they've recovered. If you're sick with symptoms of a viral infection, try to avoid exposing others.
- Wash your hands regularly. Frequent hand-washing is one of the best ways to avoid getting sick and spreading illness.
- Avoid risky behaviors. To reduce the chances of getting an HIV-related myocardial infection, practice safe sex and don't use illegal drugs.
- Get recommended vaccines. Stay up to date on the recommended vaccines, including those that protect against COVID-19, influenza and rubella — diseases that can cause myocarditis. Rarely, the COVID-19 vaccine can cause inflammation of the heart muscle (myocarditis) and inflammation of the outer heart lining (pericarditis), particularly in males ages 12 to 29. Talk to your health care provider about the benefits and risks of vaccines.