Objective To investigate the role of improved intrinsic heart rate in the diagnosis of sinoatrial node dysfunction. Methods Thirty patients were studied in our research

whose data were collected in the department of electrophysiology from January 2018 to May 2019. According to the medical history

symptoms

ambulatory ECG and clinical diagnosis results

they were divided into simple sinus bradycardia（group A） and sick sinus syndrome group（group B）. The intrinsic heart rate of the two groups was measured by the improved intrinsic heart rate measurement method

and the heart rate levels at each time point after Atropine and Esmolol were recorded respectively. The results of the improved test and atropine test were also compared by ROC curve with the Astropine test

and the correlation between the predicted value and the measured value was discussed by correlation analysis. During the follow-up of the two groups of patients

the modified test was used for comparative evaluation again. Results The intrinsic heart rate measured by the improved method was 85.75 ± 8.90bpm in group A and 72.50 ± 6.38bpm in group B. There was significant difference between the two groups（p<0.001）. The heart rate recording results after Esmolol injection showed that there were significant differences between the two groups at each time point. The ROC curve showed that the area under the curve of modified test was 0.887（95% CI: 0.770-1.000）

which was higher than atropine test（0.788

95%CI:0.606-0.969）. The comparison between the measured and predicted values of the improvement test showed that they were not correlated（p=0.814）. It was found that no significant change in the patient’s measurement after 1 year when comparing and evaluating follow-up data by the modified test. Conclusions The improved intrinsic heart rate measurement has a differential diagnostic role in the diagnosis of sinoatrial node dysfunction. Its specificity and sensitivity are better than atropine test

and it can help to screen patients with sinoatrial node dysfunction and guide clinical treatment.