It is known that heart rate is influenced by the autonomic nervous system (ANS) and an indicator of its state under various conditions, including stress. But can the ANS effect ST segment displacement under surgical stress in patient with no heart disorders?Aim: To determine significance of ANS influence on ST-segment displacement in patients during septhoplasty.Patients and methods: Analysis of the data on Holter monitoring of patients after septhoplasty was performed. Group 1 consisted of 23 patients which had both cartilaginous and bony part of nasal septum operated. Group 2 included 25 patients with only septum cartilage operated. All patients had lidocaine as local anaesthetic. Data were handled by method of standard deviation ellipses (SDE).Results: Higher variability of HR and ST segment was observed in Group 1 patients.Conclusions: The bigger size of the surgical site leads to higher ANS arousal which is manifested by higher variability of HR and ST segment. In our opinion, ST segment displacement are indirectly influenced by ANS. SDE method can be used for indirect estimation of ANS state in patient with no heart rhythm disorders, ischemic state or others heart diseases.Standard deviation ellipses