Objective:To observe the changes of the different frequency domain of heart rate variability after the partial block of the sympathetic and vagal activity and to prove the correctness of the analysis system.Methods:Six healthy volunteers were injected intravenously with metoprolol (5mg )and six with atropine (2mg).The heart electronic signals were collected 30 minutes before the injection and 30 minutes after the injection.The collection and analysis system were provided by the electrodynamic engineering college of the Chongqing University.The values of the HF

LF

VLF and ULF were assayed and the changes between two drugs and among the different time were compared.The time domain was calculated as well.Results:SDNN

rMSSD and pNN50 were increased while HRV triangle value was decreased after the injection of metoprolol.The comparative value of the HF increased from 34.45% to 50.03%(p<0.05)while the ULF decreased from 11.79% to 4.45%(P<0.05)in the first 30 minutes period after the injection of metoprolol.SDNN

rMSSD and pNN50 were decreased while HRV triangle value was increased after the injection of atropine.The comparative value of the HF was down to 4.32%(P<0.05)while the ULF was up to 80.27%(P<0.05)in the first 30 minutes period after the injection of atropine.The energy at the respective frequency spectrum was renewed as the time passed.Conclusion:ULF can reflect the relatively pure sympathetic activity in this HRV analysis system.