Autoimmune Myocarditis is an inflammation of the myocardium, the middle layer of the heart wall. Autoimmune myocarditis occurs when the body mistakingly used its own immune system to attack healthy heart cells. Signs and symptoms of myocarditis include chest pain, heart failure, abnormal heart rhythms, and shortness of breath during exercise. If myocarditis becomes severe, the pumping action of the heart weakens, and the heart won't be able to supply the rest of the body with enough blood. Clots also could form in the heart, leading to a stroke or heart attack. Several thousand people in the United Sates are diagnosed with myocarditis each year (but not necessarily autoimmune myocarditis). Diagnosis may include several different tests, including: EEG (to measure electrical activity of the heart), chest X-ray, heart biopsy, and cardiac MRI. Treatment typically involves medications to prevent heart failure. In addition, rest and low-salt diets are recommended, and steroids can be used to reduce inflammation.