Assessment of Autonomic Nervous Function with Power Spectral Analysis of Heart Rate Variability in Spinal Cord Injured Patients

Objective To investigate the autonomic activities in spinal cord injured patients, and to compare their activities according to the level and completeness of spinal cord lesions. Method Thirty-five spinal cord injured patients and thirty healthy adults participated in this study. The ECG signals were recorded at the tilt angle of 0o and 70o for 5 minutes, and power spectral analysis of Heart Rate Variability (HRV) was done at each angle. Results The data reveals two major components such as a low-frequency (LF) component (0.05∼0.15 Hz) reflecting primarily sympathetic activities with orthostatic stress, and a high- frequency (HF) component (0.2∼0.3 Hz) reflecting parasympathetic activity. In supine position, all frequency components were not significantly different regardless the level and completeness of spinal cord lesion. At 70o head-up tilt position, the LF power and heart rate didn't increase in complete tetraplegia but significantly increased in paraplegia and healthy adults (p＜0.05). However, the HF power didn't reveal any differences in four groups by decreasing significantly in all groups. Conclusion We concluded that there is an abnormal control of autonomic activities especially the sympathetic function in complete tetraiplegia, compared with paraplegia and healthy adults.ope