Myocarditis is a disease characterized by inflammation and damage of the heart muscle. Experts believe that 5% to 20% of all cases of sudden cardiac death in children and young adults are due to myocarditis. The cause of myocarditis is usually a viral infection or a self-directed immune response. Myocarditis generally attacks otherwise healthy people. Most cases of the disease have no symptoms and are only identified by an electrocardiogram or blood tests that detect heart injury. Because myocarditis is rare, the best way to diagnose and treat the disease is not yet known but research is being done.
Many viruses can cause myocarditis but the most common are those associated with upper respiratory tract infections. Less commonly, other contagious conditions, including Lyme disease, may cause myocarditis. However, most cases of myocarditis are not infectious. There is no known risk of infection to family members of people with myocarditis. Neither is myocarditis believed to be inherited. No genes are known to predispose people to myocarditis. Because myocarditis is rare, information regarding causes and effective treatments is still limited.
What are the Symptoms of Myocarditis?
The most common symptom of myocarditis is shortness of breath during exercise or exertion. This symptom usually develops seven to 14 days after a viral illness and can progress to shortness of breath at night, which may require the person to sit up to breathe. Other symptoms 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 and sudden loss of consciousness.
Most known cases of myocarditis have no symptoms and are not diagnosed until death. (Experts believe that an important portion of "unknown" cases of sudden cardiac death in the young are due to myocarditis). However, when a person develops symptoms, common tests for myocarditis include an electrocardiogram, a chest X-ray, an echocardiogram, a cardiac magnetic resonance imaging (MRI) scan, and occasionally, a heart biopsy.
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