Myocarditis is an inflammation of the muscular walls of the heart. Inflammation causes damage to the individual heart muscle cells.
What starts the inflammation is not always known. When the cause of myocarditis is not known it is called idiopathic.
Causes of myocarditis include infection and allergic reactions to drugs. The most common cause of myocarditis is a viral infection. Myocarditis may occur as a side effect of cancer treatment with radiation and certain drugs. It may also be caused by exposure to certain chemicals. Although rare, myocarditis can also be caused by the germ that causes Lyme disease. In some parts of the world, a parasite often causes it. Some of the damage may occur from an over-reaction of the body's immune system.
When too many heart muscle cells are damaged, the heart can't pump effectively. The process may be rapid and may result in death. More commonly, the heart begins to heal itself. Heart muscle heals by changing dead cells to scar tissue. Scar tissue does not contract and can't help the heart to pump. If enough scar tissue forms, heart failure may result.
The first test you will have is usually an echocardiogram.
Myocarditis can best be diagnosed by examining a small piece of heart muscle under a microscope. Samples of the heart muscle are taken with a bioptome. A bioptome is a thin, flexible tube with small cutting jaws at its tip. The bioptome is inserted through a vein in your neck and positioned in the heart. Once the bioptome is in position, the cutting jaws withdraw very small heart muscle samples for analysis. You will be given a shot to numb the area where the bioptome is inserted, but you will remain awake. You may experience minor discomfort but the procedure is usually painless. Results will be available within 48 hours.
Once myocarditis is diagnosed, blood tests might be done to try to find out if infection is the cause, and which germ caused the infection.
The goals of treatment are to support the function of the heart as it heals itself and to reduce the amount of damage as much as possible. Drugs, and sometimes a device called an intra-aortic balloon pump, are used. Complications of myocarditis, like heart failure, can be treated if they occur.
About one-third of people affected will return to normal over several weeks to several months. The rest will have permanent damage to the heart muscle. The amount of damage varies from slight to more severe. The amount of permanent damage is hard to predict. There are effective treatments for patients whose hearts do not return to normal.
Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional.
HIA File CRD3641F.HTM Release 9.0/2006
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