Myocarditis Foundation

Discover Myocarditis Causes, Symptoms, Diagnosis and Treatment

About Myocarditis

About Myocarditis

Myocarditis is a disease marked by inflammation and damage of the heart muscle. Although the exact incidence of myocarditis is not known, it is estimated that several thousand patients per year are diagnosed in the United States. Myocarditis usually attacks otherwise healthy people. It is believed that 5 to 20% of all cases of sudden death in young adults are due to myocarditis.

There are many causes of myocarditis, including viral infections, autoimmune diseases, environmental toxins, and adverse reactions to medications. The prognosis is variable but chronic heart failure is the major long term complication. Myocarditis and the associated disorder of idiopathic dilated cardiomyopathy are the cause of approximately 45% of heart transplants in the United States.

This information is meant to help you understand myocarditis. If you have questions about this information or about your condition, talk to a member of your health-care team.

More Myocarditis Information

About Your Heart

Your heart is a four-chambered, muscular pump about the size of an adult fist. Normally, the heart beats 60 to 100 times per minute, pumping blood throughout your body with each beat.

Two upper heart chambers called the right and left atria (each is called an atrium) receive blood that returns to the heart from the body. Veins carry this returning blood to the atria. When the muscles of the atria contract, blood is squeezed into the two larger, lower heart chambers called the right and left ventricles. When the muscles of the ventricles contract, blood is propelled through arteries to the entire body. The pumping of the ventricles creates the pulse you feel in your wrist or neck.

What is Myocarditis?


Myocarditis in a mouse heart. Cardiac inflammation stains purple.

Myocarditis is uncommon and can be caused by a viral infection or a self-directed immune response (this is when the person’s own immune system attacks the body, such as in autoimmune diseases like rheumatoid arthritis or lupus). Some autoimmune diseases can affect the heart and cause myocarditis. Rare cases have also been associated with a variety of infections, toxic injuries, adverse drug reactions, and even cancer.



What Causes Myocarditis?

Myocarditis can be caused by many viruses, but the most common are those associated with upper respiratory tract infections. Less commonly, other contagious diseases, including Lyme disease, may cause myocarditis. Rarely, myocarditis has been caused by cocaine use or exposure to toxic agents including metal poisons or snake or spider bites.

Most cases of myocarditis are not infectious. There is no known risk of infection to family members of people with myocarditis.

What are the Symptoms of Myocarditis?

The most common symptom of myocarditis is shortness of breath during exercise or exertion. This symptom usually develops 7 to 14 days after a viral illness and can progress to shortness of breath at night, which may require that you sit up to breathe.

Other symptoms may include fatigue, heart palpitations and chest pain or pressure. The legs also may swell. Rarely, myocarditis causes a sudden loss of consciousness that may be due to abnormal heart rhythms. In summary, patients may experience some, all or none of the following symptoms: shortness of breath, chest pain, lightheadedness, irregular heartbeat, sudden loss of consciousness.

How is Myocarditis Diagnosed?

The majority of cases of myocarditis have no symptoms and are not diagnosed.  However, when a person develops symptoms, common tests for myocarditis include the following:

How is Myocarditis Treated?

Myocarditis is commonly treated with medications used to treat heart failure. Rest and a low-salt diet are often recommended. Steroids and other medications also may be used to reduce heart inflammation.

More rarely, if an abnormal heart rhythm is present, treatment may require additional medications, a pacemaker or even a defibrillator.

Discuss treatment options with your health-care team.

What are the Long-Term Effects of Myocarditis?

The long-term effects of myocarditis are highly variable. Many people recover heart function without long-term negative health effects and without a return of symptoms. In a minority of cases, heart function may not improve after myocarditis, and the individual can require long-term medical therapy and sometimes heart transplantation.

Can Myocarditis Recur?

Yes, myocarditis can recur, and in some cases can lead to a chronically enlarged heart (called dilated cardiomyopathy). There is no known way to prevent recurrence of myocarditis. However, the risk of recurrence is low (probably about 10 to 15 percent).

What Can be Done to Prevent Myocarditis?

No lifestyle changes or medical treatments are known to prevent viral myocarditis.

Because myocarditis is rare, information is limited regarding its causes and effective treatments. Myocarditis is not believed to be inherited. No genes are known to predispose people to myocarditis.

Learn more about giant cell myocarditis or browse myocarditis FAQs, myocarditis research articles and myocarditis research photos.