The R-MSSD value is 22 within the normal range of values. R-MSSD is the root mean square of the difference between adjacent normal cardiac cycles, and the normal range is (27±12) ms. RMSSD, SDANN, and SDNN are all indicators of heart rate variability in patients with coronary artery disease, and HRV can be used as a sensitive indicator to reflect the fine regulation of the cardiovascular system by neurohumoral factors. At present, HRV can make a correct judgment on the condition of many diseases by judging the change of patients’ heart rate, and to a certain extent, it can prevent the deterioration of the disease, such as cardiovascular diseases, such as hypertension, myocardial infarction and so on, which will cause the abnormality of the RMSSD and the decrease of the HRV. When the patient’s heart rate variability index has problems, it is recommended to go to the hospital immediately.