Myocarditis is a disease caused by infection or other causes of diffuse or focal inflammatory cell infiltration of the myocardial interstitium and adjacent myocardial fiber necrosis or degeneration, resulting in varying degrees of cardiac dysfunction and other systemic damage. Viruses are the main cause of myocarditis, but other agents such as bacteria, mycoplasma, protozoa, fungi, chlamydia, as well as poisoning and allergies, can cause the disease. Most viral causes are asymptomatic, but a very small number of severe cases can be fatal due to fulminant myocarditis. Patients with acute viral myocarditis tend to have normal heart anatomy and no previous history of heart disease. If a child has myocarditis, the signs and symptoms are as follows: 1. Symptoms: Mild cases are asymptomatic or show non-specific symptoms such as weakness, excessive sweating, palpitations, shortness of breath, dizziness, chest tightness, and pallor. In severe cases, heart failure, A – S syndrome, cardiogenic shock and sudden death may occur. 2. Signs: Weak or split first heart sound, may have gallop rhythm, tachycardia or bradycardia, or arrhythmia, decreased blood pressure, and low pulse pressure. In mild cases, there is usually no heart enlargement, but in severe cases, there may be mild to moderate heart enlargement, and if there is also pericardial involvement, pericardial rub sounds may be heard. In combination with heart failure, there may be wet rales in the lungs, jugular venous anger, liver enlargement, and bilateral lower extremity edema. Signs of cardiogenic shock may be seen in severe cases.