Myocarditis is an inflammatory disease of the myocardium, most commonly caused by viral infections. The onset of the disease can be either sudden or slow, and it is mostly self-limiting, but in rare cases can lead to acute pump failure or sudden death. The severity of the condition largely depends on the extent and location of the lesions. Mild cases may have no symptoms at all, while severe cases can lead to cardiogenic shock or even sudden death. In clinical diagnosis, the majority of myocarditis cases present primarily with arrhythmias, and in a minority of cases, the initial symptoms may include syncope or Adams-Stokes syndrome. Thus, the severity of myocarditis is related to the variation in the condition itself.