Myocarditis is an inflammation of the muscle tissue of the heart. Initially, the symptoms are mild and vague, with fatigue, shortness of breath, and occasional palpitations occurring. Heart failure may develop and blood clots form.

The causes of myocarditis include various infections; some conditions such as lupus or rheumatic fever; and certain drugs, particularly those used in the treatment of cancer. Treatment typically focuses upon the cause once it is discovered. The patient often requires complete bed rest and may even require oxygen. Corticosteroids may be used.