The normal heart contraction is caused by the contraction of the atria and ventricles after the excitation of electrical activity, and then the blood is ejected outwardly and hits the pulse, so the heart rate can be understood by feeling the frequency of the pulse. Under normal circumstances, the heart rate is equal to the pulse rate, which generally fluctuates about 60-100 times per minute. When atrial fibrillation occurs, the electrical activity of the atria is disturbed, and the sequential contraction of the atria and ventricles of the heart disappears, and the contraction of the heart is unequal in strength at this time, so the pulse that is felt is sporadic. In this case, the pulse frequency is less than the heart rate, i.e., short pulse. When atrial fibrillation occurs, the range of frequency fluctuation is greater than that of normal sinus rhythm, and the frequency of atrial fibrillation can even reach 100 times per minute when it is fast, and patients often experience varying degrees of panic, shortness of breath, and dyspnea at this time. Sometimes when atrial fibrillation occurs in combination with atrioventricular node insufficiency or problems with the left and right bundle branches, the pulse rate will be lower or even have long intervals, even >3 seconds or 5 seconds, and this will show varying degrees of insufficient blood supply to the heart. If it is any longer, syncope will occur, so the range of heart rate variation in atrial fibrillation is large. If atrial fibrillation occurs, it is important to do 24-hour ambulatory monitoring to understand the range of variation and then give targeted treatment.