Systemic vascular resistance is increased and associated with accelerated arterial stiffening change in patients with chronic cervical spinal cord injury

Background: Despite of stiffening change of conduit arteries, how total peripheral resistance (TPR) is adapted to chronic spinal cord injury (SCI) remains unclear. Aim: To investigate how chronic cervical SCI influences hemodynamic characteristics Design: Cross-sectional, case-control study Setting: Rehabilitation department in the tertiary medical center Population: Twenty-one male patients with traumatic SCI resulting from cervical spine fracture were recruited. The injury occurred three to 289 months (46 months in average) previously. Twenty-one healthy male participants with matched age and body mass index were enrolled as control group. Methods: The subjects were asked to maintain supine rest (SR) and then head-up tilt (HUT) at 60 degree for five minutes, respectively. A novel noninvasive bioreactance device was employed to measure cardiac hemodynamics, whereas heart rate variability was used to determine cardiac autonomic activity. Additionally, the digital volume pulse analysis was applied to calculate arterial stiffness index (SI) and arteriolar reflection index (RI). Results: SCI patients revealed less stroke volume and cardiac output (CO), as well as, greater total peripheral resistance (TPR) and SI during SR than normal subjects did. Moreover, the positive correlation between TPR and SI was observed in SCI patients rather than normal subjects. In SCI patients, HUT 1) markedly decreased TPR while CO and cardio-acceleration responses remained intact and 2) decreased HF power value but failed to change LF/HF ratio. Furthermore, the degree of orthostatic hypotension was correlated with the TPR_HUT/TPR_SR ratio but not the CO _HUT/CO_SR ratio. Conclusions: Chronic cervical SCI leads to a progressively accelerated increase in vascular stiffness, which is associated with increase in systemic vascular resistance. Furthermore, the cervical SCI-related orthostatic hypotension lies in the impairment of vasoconstriction without cardiac dysfunction. Clinical Rehabilitation Impact: SI, rather than blood pressure, reflects not only cardiovascular risk but also TPR in chronic cervical SCI.