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What is Myocarditis?

Myocarditis is a disorder characterized by inflammation of the heart muscle, also known as the myocardium. This reduces your heart's ability to pump sufficient blood throughout the body and also causes abnormal or rapid heart rhythms (arrhythmias). Extreme cases may cause blood clots leading to a stroke or heart attack.


In most cases, the exact cause of myocarditis is not found. When the cause is found, infection is often the reason. The type of infection may be one of the following:

  • Viral
  • Bacterial
  • Parasitic
  • Fungal

Other causes can include:

  • Allergic reactions to medications used to treat cancer, anti-seizure medications, antibiotics such as penicillin, and some illegal substances, such as cocaine.
  • Exposure to certain chemicals or radiation such as carbon monoxide.
  • Other diseases such as lupus and giant cell arteritis.


Mild cases or early stages might have no symptoms at all. In serious cases, symptoms vary depending upon the cause. Some common symptoms include:

  • Rapid or abnormal heart rhythms
  • Shortness of breath
  • Swelling of your legs, feet, and ankles
  • Tiredness
  • Chest pain
  • Other symptoms of a viral infection which include body aches, joint pain, headache, sore throat, fever, or diarrhea


To diagnose myocarditis, your doctor may carry out a physical examination. Your doctor may order other tests to confirm the diagnosis, which includes:

  • Electrocardiogram (ECG): a painless test that detects and records your heart's electrical activity
  • Chest X-ray
  • Blood tests to measure white and red blood cell counts, and certain enzyme levels which indicate heart muscle damage and detect antibodies against viruses or other harmful microorganisms
  • Echocardiography or MRI to view the size, structure, and movement of the heart
  • Cardiac catheterization and endomyocardial biopsy


Treatment depends on the source and severity of the myocardial inflammation. Treatment involves:

  • Certain medications
  • Corticosteroid therapy to help reduce inflammation
  • Implantable cardioverter-defibrillator (ICD) or pacemaker
  • Behavioral changes, such as rest, fluid restriction, or reduced activity for at least 6 months and a low-salt diet