Patients with myocarditis usually have a rapid heartbeat. There are several factors that cause a rapid heartbeat: First, patients usually suffer from myocarditis triggered by bacterial or viral infections. The human body causes an antigenic antibody response when bacteria, viruses or other microorganisms invade the body, and these pathogens cause a high body temperature in the body, and the patient will have a rapid heartbeat when the body temperature is high. Second, when a patient has myocarditis, there is a significant lack of blood and oxygen supply to the heart muscle cells, which can also lead to a series of symptoms such as tachycardia and arrhythmia. Then, if the patient has acute fulminant severe myocarditis, the myocardial cells will experience massive ischemia, hypoxia, or even apoptosis, and compensatory tachycardia will occur. So with severe myocarditis, there are usually significant arrhythmias, with tachycardia predominating.