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

ABSTRACT

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.