Myocarditis (otherwise known as inflammatory cardiomyopathy) is inflammation of the myocardium (heart muscle) that has a broad variety of clinical presentation from mild to devastating.
Usually, myocarditis is the results of a viral infection. However, it can also be caused by non-viral pathogens and hypersensitivity to drugs. The central feature of myocarditis is an inflammatory infiltrate which causes damage to the myocardium without blocking the coronary arteries. In some cases myocarditis can result in necrosis (death) of heart cells; however, it is not always the case.
Despite being usually caused by viral or non-viral agents, in essence myocarditis is often an autoimmune reaction. Certain proteins of microbes closely resemble the cardiac myosin (ATP-dependent motor protein responsible for muscle contraction). This causes the immune system to attack cardiac myosin after it was sensitized by the microbial infection.
Unfortunately, a definitive diagnosis can only be made after heart biopsy, which is rarely made due to it being too invasive. The consequences of myocarditis vary greatly from person to person. A mild case of myocarditis can pass unnoticed and only be noticed on autopsy after the person has died due to some other reason. In other cases myocarditis can lead to severe chest pain, heart failure and sudden death. Loss of right ventricular function and high-degree heart block are especially deadly.