Low PR is generally defined as an ECG PR interval that is too short, less than 120ms, and may be associated with short PR syndrome, arrhythmias, and other conditions. The electrocardiogram recorded from a single heartbeat can be categorized into P, Q, R, S, and T waves according to their waveforms, each of which is a part of the electrocardiogram for that heartbeat.The PR interval refers to the distance from the P waveform to the beginning of the QRS wave cluster. The PR interval is usually considered too low when it is less than 120ms. If a low PR is found only during ECG measurement without any discomfort, it is usually associated with short PR syndrome, in which the patient has a structural abnormality of the heart that results in abnormal electrical signal conduction, and usually requires no treatment. If symptoms such as obvious panic, palpitations and dizziness occur, they are often related to arrhythmia and require early hospitalization to clarify the cause and provide targeted treatment or therapy.