Characterizing cardiovascular autonomic dysfunction in individuals with spinal cord injury

Society for Neuroscience Chicago 2015 Nanosymposium Energy Metabolism and Cardiovascular Regulation Autonomic Regulation
Authors: *S. WANG1, S. ASLAN1,2, C. FERREIRA1, J. GUNTER1, J. WYLES1, D. WANG1, S. HARKEMA1,2; 1Dept. of Neurolog. Surgery, Univ. of Louisville, Louisville, KY; 2Neurosci. Collaborative Ctr., Frazier Rehab Inst., Louisville, KY

Recognizing the pattern of autonomic control of the heart and blood vessels is a prerequisite for an effective treatment of abnormal blood pressure (BP) regulation in individuals with spinal cord injury (SCI). The goal of this study was to characterize short-term BP and heart rate (HR) responses to orthostatic stress (sit-up test) in individuals with SCI independent of their diagnoses of sensory-motor impairment scale and level. Continuous finger BP and HR were recorded from 20 subjects with AIS scale graded A, B, C or D, and neural level ranged from C3 to T11, during 15 minutes of supine rest followed by a quick passive sit-up and 15 minutes of quiet sitting. There were diverse BP and HR responses to orthostatic stress among individuals. Specifically, 1) two had normal increases in HR and BP in response to upright position. 2) Four developed orthostatic hypotension with a normal increase in HR. 3) Six had normal increases in HR but no or inadequate BP response. 4) Two had higher than normal HR response but inadequate BP response. 5) Five had no significant HR response but had a BP response. 6) One had no HR or BP response. 7) Finally, one had unstable systolic and diastolic BP responses. We further investigated sympathetic (SNS) and parasympathetic (PNS) control of HR and SNS control of peripheral vasomotion by using indirect indexes from spectral analysis. Results showed that 1) in the four with orthostatic hypotension, responses in index of SNS modulation of vasomotion (low-frequency power of diastolic BP) were lower than other subjects, indicating impaired SNS control of vasomotion below injury level. 2) Responses in SNS modulation of vasomotion were correlated with responses in systolic BP among all subjects (r = 0.46, p < 0.05) but were not correlated with completeness of sensory-motor injury.3) In the five with no HR response but had a BP response, shift of cardiac sympatho-vagal balance to SNS dominance (low to high frequency ratio of HR power) were lower than other subjects, indicating impaired SNS control of HR in these subjects. 4) Responses in cardiac sympatho-vagal balance were correlated with HR responses among all subjects (r = 0.64, p<0.004) but were not correlated with completeness of sensory-motor injury. These results confirmed impaired SNS control of HR and peripheral vasomotion after SCI and the usefulness of indirect measures of autonomic functions to assess autonomic impairment, and also indicated the importance of recognizing the pattern of autonomic impairment in individuals with SCI independent of their diagnoses of AIS scale and neural level. Larger number of subjects is needed to further characterize the diverse pattern of autonomic regulation after SCI.

Support: Commonwealth of Kentucky Challenge for Excellence Trust Fund Leona M. and Harry B. Helmsley Charitable Trust NIH Grant 5 P30 GM103507 Craig H. Neilsen Foundation University of Louisville Foundation Jewish Hospital and St. Mary’s Foundation Kentucky Spinal Cord Injury Research Center
Disclosures: S. Wang: None. S. Aslan: None. C. Ferreira: None. J. Gunter: None. J. Wyles: None. D. Wang: None. S. Harkema: None.

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