Alternative names
Inflammation - heart muscle; Cardiomyopathy

Myocarditis is an inflammation of the heart muscle.

Causes, incidence, and risk factors

Myocarditis is an uncommon disorder caused by viral infections such as coxsackie virus, adenovirus, and echovirus. It may also occur during or after various viral, bacterial, or parasitic infections (such as polio, influenza, or rubella).

The condition may be caused by exposure to chemicals or allergic reactions to certain medications and it can be associated with autoimmune diseases.

The heart muscle becomes inflamed and weakened, causing symptoms of heart failure, which may mimic a heart attack.


  • History of preceding viral illness  
  • Fever  
  • Chest pain that may resemble a heart attack  
  • Joint pain/swelling  
  • Abnormal heart beats  
  • Fatigue  
  • Shortness of breath  
  • Leg edema  
  • Inability to lie flat

Total absence of symptoms is common

Additional symptoms that may be associated with this disease:

  • Syncope (fainting), often related to arrhythmias  
  • Decreased urine output  
  • Other symtoms consistent with a viral infection - headache, muscle aches, diarrhea, sore throat, rashes

Signs and tests
A physical examination may detect a rapid heartbeat (tachycardia) or abnormal heart beats, abnormal heart sounds (murmurs, extra heart sounds), fluid in the lungs and fluid in the skin of the legs. In addition, other signs suggestive of an infection may be present: fever, rashes, red throat, itchy eyes, swollen joints.

Tests used in the diagnosis of myocarditis include:

  • Electrocardiogram (ECG)  
  • Chest X-ray  
  • Ultrasound of the heart (echocardiogram) - may show weak heart muscle, an enlarged heart, or fluid surrounding the heart.  
  • White blood cell count  
  • Red blood cell count  
  • Blood cultures for infection  
  • Blood tests for antibodies against the heart muscle and the body itself  
  • Heart muscle biopsy - rarely performed


Treatment includes evaluation and treatment of underlying cause. This may require use of antibiotics, reduced level of activity, and low-salt diet. Steroids and other medications may be used to reduce inflammation. Diuretics (medicine to promote removal of body water via the urine) are also given.

If the heart muscle is very weak, standard medicines to treat heart failure are also used. Abnormal heart rhythm may require the use of additional medications, a pacemaker or even a defibrillator. If a blood clot is present in the heart chamber, blood thinning medicine is given as well.

Expectations (prognosis)
Myocarditis is very variable and the prognosis depends on the cause and the individual patient. Some may recover completely, while others may have permanent heart failure.


  • Heart failure  
  • Pericarditis  
  • Cardiomyopathy

Calling your health care provider
Call your health care provider if symptoms of myocarditis occur, especially after a recent infection.

If you have myocarditis, call your health care provider (or get to the emergency room if symptoms are severe) if you experience increased swelling, chest pain, difficulty breathing, or other new symptoms.

Prompt treatment of causative disorders may reduce the risk of myocarditis.

Johns Hopkins patient information

Last revised: December 3, 2012
by Levon Ter-Markosyan, D.M.D.

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