Most patients with myocarditis have prodromal infection symptoms, and the clinical presentation varies depending on the extensiveness of the myocardial lesion. If the prodromal phase is an upper respiratory tract infection, there is usually fever, sore throat, and cough. If it is a gastrointestinal infection, it will manifest with diarrhea, vomiting, muscle aches, and fever. Myocarditis does not always show obvious symptoms, and some cases have atypical manifestations, especially in relatively mild cases of myocarditis, where the patient may simply present with palpitations. When myocardial involvement is more extensive, patients tend to feel palpitations and chest tightness, and if inflammation involves the pleura and pericardium, there is often significant chest pain; severe myocarditis can lead to cardiogenic shock and sudden death. These patients tend to have dyspnea, edema, or even syncope and sudden death after prodromal symptoms, often due to severe arrhythmias, heart failure, and cardiogenic shock caused by extensive acute myocardial damage. Depending on the clinical manifestations, myocarditis can be clinically classified as mild, subclinical, insidiously progressive, acute dilated cardiomyopathy, atrioventricular block, cool myocardial infarction, and sudden death. Patients with myocarditis have a variety of clinical manifestations, and thus it is less likely to rely on symptoms alone to diagnose myocarditis.