Myocarditis

Myocarditis or inflammatory cardiomyopathy is inflammation of heart muscle. The consequences of myocarditis vary widely. It can cause a mild disease without any symptoms that resolves itself, or it may cause chest pain, heart failure, or sudden death. An acute myocardial infarction-like syndrome with normal coronary arteries has a good prognosis. Heart failure, even with a dilated left ventricle, may have a good prognosis. Ventricular arrhythmias and high-degree heart block have a poor prognosis. Loss of right ventricular function is a strong predictor of death.

Myocarditis is most often due to infection by common viruses, such as parvovirus B19, less commonly nonviral pathogens such as Borrelia burgdorferi (Lyme disease) or Trypanosoma cruzi, or as a hypersensitivity response to drugs. Myocarditis can sometimes be an autoimmune disease. Streptococcal M protein and coxsackievirus B have regions that are similar to the myosin protein found in the heart muscle. During and after the infection, the immune system may attack cardiac myosin. Myocarditis may or may not include death (necrosis) of heart tissue. It may include dilated cardiomyopathy. A definitive diagnosis requires a heart biopsy.