The normal PR interval time limit is not less than 0.12s. A PR interval lower than 0.12s is a low or shortened PR interval, which needs to be combined with clinical manifestations to diagnose the disease. The most common type of PR interval shortening is short PR syndrome, which does not have typical clinical significance. Patients are advised to recheck the ECG within 3 days, and further cardiac testing is required if it is accompanied by an accelerated heart rate or arrhythmia. If the patient has a shortened PR interval in a quiet state, it means that there is insufficient blood supply to the heart muscle, which can lead to functional arrhythmia. If the patient is an elderly person, he can be treated with intravenous infusion of Dan Hong injection. He needs to protect his heart, avoid straining and staying up late at night, and take heart medications regularly.