The full name of hr is heart,rate, which means low heart rate. If the heart rate is low over a long period of time, it is an independent risk factor for stroke and heart attack. The first thing is to do a long-duration ambulatory ECG monitoring, that is to say, there are 24 hours, 48 hours, 72 hours or even longer ambulatory ECG. For example, betalactam, digoxin and other drugs. In addition, we should also rule out the cause of the machine to see if there is a machine error caused. Second, to rule out pathological causes, the pathological causes are mainly the following: 1. Sinus arrest occurs at night, most commonly at night, some for 8 or 9 seconds or even 10 seconds, usually requiring a pacemaker; 2. Block, which occurs at night, is also common due to vagal excitation. For example, II degree type I, II degree type II, and even some people will have high atrioventricular block, paroxysmal complete atrioventricular block, according to the clinical assessment, to see if there is a possibility of installing a pacemaker; 3, the heart rate is slow, sometimes the heart rate can exceed 90 beats/min, especially in sinus rhythm can exceed 90 beats/min, indicating that the sinus node is still possible, may be Vagus nerve overexcitation regulation caused, it is best to strengthen the exercise, through exercise to improve the heart rate reserve.