Overview

Myocarditis is an inflammation of the heart muscle (myocardium). The inflammation can reduce your heart's ability to pump and cause rapid or abnormal heart rhythms (arrhythmias).

Infection with a virus usually causes myocarditis. Sometimes myocarditis can result from a reaction to a drug or be part of a more general inflammatory condition. Signs and symptoms include chest pain, fatigue, shortness of breath, and rapid or irregular heartbeats.

Severe myocarditis weakens your heart so that the rest of your body doesn't get enough blood. Clots can form in your heart, leading to a stroke or heart attack.

Treatment for myocarditis depends on the cause.

Symptoms

If you're in the early stages of myocarditis, you might have mild symptoms such as chest pain, rapid or irregular heartbeats, or shortness of breath. Some people with early-stage myocarditis don't have any symptoms.

The signs and symptoms of myocarditis vary, depending on the cause of the disease. Common myocarditis signs and symptoms include:

  • Chest pain
  • Rapid or abnormal heartbeat (arrhythmias)
  • Shortness of breath, at rest or during activity
  • Fluid buildup with swelling of your legs, ankles and feet
  • Fatigue
  • Other signs and symptoms of a viral infection such as a headache, body aches, joint pain, fever, a sore throat or diarrhea

Sometimes, myocarditis symptoms may be similar to 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, they might have signs and symptoms including:

  • Fever
  • Fainting
  • Breathing difficulties
  • Rapid breathing
  • Chest pain
  • Rapid or abnormal heart rhythms (arrhythmias)

When to see a doctor

Contact your doctor if you have symptoms of myocarditis, particularly chest pain and shortness of breath. Symptoms of myocarditis can resemble a heart attack. Get emergency medical help if you have unexplained chest pain and shortness of breath.

If you've had an infection, watch for the symptoms of myocarditis and let your doctor know if they occur. If you have severe symptoms, go to the emergency room or call for emergency medical help.

Causes

Often, the cause of myocarditis isn't identified. There are many potential causes but the risk of developing myocarditis is rare.

Potential causes of myocarditis include:

  • Viruses. Many viruses are commonly associated with myocarditis, including the viruses 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. It's also common in people with HIV, the virus that causes AIDS.

  • Bacteria. Bacteria that can cause myocarditis include staphylococcus, streptococcus, the bacterium that causes diphtheria and the tick-borne bacterium responsible for Lyme disease.
  • 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. Chagas disease is much more common in Central and South America than in the United States, but it can occur in travelers and in immigrants from that part of the world.
  • Fungi. Yeast infections, such as candida; molds, such as aspergillus; and other fungi, such as histoplasma, often found in bird droppings, can sometimes cause myocarditis, particularly in people with weakened immune systems.

Myocarditis also sometimes occurs if you're exposed to:

  • Medications or illegal drugs that might cause an allergic or toxic reaction. These include drugs used to treat cancer; antibiotics, such as penicillin and sulfonamide drugs; some anti-seizure medications; and some illegal substances, such as cocaine.
  • Chemicals or radiation. Exposure to certain chemicals, such as carbon monoxide, and radiation can sometimes cause myocarditis.
  • Other diseases. These include disorders such as lupus, Wegener's granulomatosis, giant cell arteritis and Takayasu's arteritis.

Complications

Usually, myocarditis goes away without permanent complications. However, severe myocarditis can permanently damage your heart muscle, possibly causing:

  • Heart failure. Untreated, myocarditis can damage your heart's muscle so that it can't pump blood effectively. In severe cases, myocarditis-related heart failure may require a ventricular assist device or a heart transplant.
  • Heart attack or stroke. If your heart's muscle is injured and can't pump blood, the blood that collects in your heart can form clots. If a clot blocks one of your heart's arteries, you can have a heart attack. If a blood clot in your heart travels to an artery leading to your brain, you can have a stroke.
  • Rapid or abnormal heart rhythms (arrhythmias). Damage to your heart muscle can cause an abnormal heart rhythm.
  • Sudden cardiac death. Certain serious arrhythmias can cause your heart to stop beating (sudden cardiac arrest). It's deadly if not treated immediately.

Prevention

There's no specific prevention for myocarditis. However, taking these steps to prevent infections might help:

  • Avoid people who have a viral or flu-like illness until they've recovered. If you're sick with symptoms of a viral infection, try to avoid exposing others.
  • Follow good hygiene. Regular hand-washing can help prevent spreading illness.
  • Avoid risky behaviors. To reduce your chances of getting an HIV-related myocardial infection, practice safe sex and don't use illegal drugs.
  • Minimize exposure to ticks. If you spend time in tick-infested areas, wear long-sleeved shirts and long pants to cover as much of your skin as possible. Apply tick or insect repellents that contain DEET.
  • Get your vaccines. Stay up to date on the recommended vaccines, including those that protect against COVID-19, rubella and influenza — diseases that can cause myocarditis.