Altered Mayer Wave and Baroreflex Profiles in High Spinal Cord Injury

Spinal sympathetic neurons are distributed in cord seg-ments from Th1 to L3. High spinal cord injury demon-strates severe orthostatic hypotension, but not lower cord injury. It remains to be clarified as to where is the critical spinal level disturbing neural cardiovascular regulations in response to orthostatic stress. To address this issue, beat-to-beat blood pressure (BP) (measured using a Finapres device) and RR interval (measured electrocardiographi-cally) were recorded at rest and in a 60 ° head-up position in 26 patients with varying levels of spinal cord injury (C4 to Th12) and in 15 healthy (control) subjects. Sympathetic vascular tone was examined by the Mayer wave power spectrum of systolic blood pressure (SBP) variability. Baroreflex sensitivity was examined by transfer function analysis of SBP and RR interval variabilities. The Maye