Clinical correlates of frequency analyses of cardiovascular control after spinal cord injury

Abstract

Claydon VE, Krassioukov AV. Clinical correlates of frequency analyses of cardiovascular control after spinal cord injury. Am J Physiol Heart Circ Physiol 294: H668 -H678, 2008. First published November 16, 2007 doi:10.1152/ajpheart.00869.2007.-Spinal cord injury (SCI) has profound effects on cardiovascular autonomic function due to injury to descending autonomic pathways, and cardiovascular diseases are the leading causes of morbidity and mortality after SCI. Evaluation of cardiovascular autonomic dysfunction after SCI and appraisal of simple noninvasive autonomic assessments that are clinically meaningful would be useful to SCI clinicians and researchers. We aimed to assess supine and upright cardiovascular autonomic function from frequency analyses of heart rate and blood pressure variability (HRV and BPV) after SCI. We studied 26 subjects with chronic cervical or thoracic SCI and 17 able-bodied controls. We continuously recorded R-R interval (RRI, by ECG) and beat-to-beat blood pressure (by Finometer) in supine and seated positions. Cardiovascular control was assessed from spectral analysis of RRI and blood pressure time series. Cardiac baroreflex control was assessed from cross-spectral analyses of low-frequency spectra. Supine and upright low-frequency HRV and BPV were reduced in cervical SCI subjects, as were total BPV and HRV. Supine high-frequency HRV was reduced in thoracic SCI subjects. Cardiac baroreflex delay was increased in cervical SCI subjects. Supine frequency domain indexes were correlated with sympathetic skin responses, orthostatic cardiovascular responses, and plasma catecholamine levels. SCI results in reduced sympathetic drive to the heart and vasculature and increased baroreflex delay in cervical SCI subjects and reduced cardiac vagal tone in thoracic SCI subjects. Frequency analyses of autonomic function are related to clinical measures of autonomic control after SCI and provide useful noninvasive clinical tools with which to assess autonomic completeness of injury following SCI. baroreceptor reflex; autonomic nervous system; spectral analysis SPINAL CORD INJURY (SCI) is associated with abnormal cardiovascular control that is related to the level and severity of injury to descending autonomic (sympathetic) pathways (10,15,35). The leading cause of morbidity and mortality in SCI individuals is cardiovascular disease (16,45). This most commonly manifests as neurogenic shock (in acute SCI) (35); supine hypotension (35); orthostatic hypotension (marked decreases in blood pressure in the upright position) (10, 11); autonomic dysreflexia (profound and life-threatening blood pressure increases following afferent stimulation below the lesion) (35); ECG abnormalities and arrhythmia (38), particularly during autonomic dysreflexia (9, 14); and abnormal cardiovascular responses to exercise (8).The severe impact of cardiovascular dysfunction on quality of life after SCI has prompted the search for simple physiological bedside assessments of autonomic function that can easily be performed in the clin...

Assessment of autonomic function after acute spinal cord injury using heart rate variability analyses

“…Other studies have likewise demonstrated loss of LFP in SCI patients. 2,13,14 Pagani et al 19 showed that chronic, but not acute, β-adrenergic receptor blockade reduced LFP at rest; thereby suggesting that sympathetic innervation of the heart is instrumental in the genesis of the LFP component.…”

Modulação autonômica durante o exercício incremental com membros superiores em indivíduos com lesão medular

“…However, significant differences between the SCI and the other groups have not been found for the HRV at rest in the present study. Probably, these controversial results compared to the literature (18,19) may be due to the physical fitness level of the individuals from the SCI group, who were wheelchair basketball practitioners. Some studies suggest that individuals with better physical fitness present higher HRV at rest (25) .…”

“…On the other hand, it was expected that the SCI group presented lower HRV values at rest than the other groups (18,19) . However, significant differences between the SCI and the other groups have not been found for the HRV at rest in the present study.…”

“…For example, individuals with spinal cord injury (SCI) present deficit in motor control and limited capacity of performing daily tasks, which increases the incidence of cardiac complications and alterations in the neural control of the cardiac muscle (17) . Some studies report that individuals with spinal cord injury present HRV reduction (18,19) and increase of the heart rate (HR) at rest (20) . These results suggest increase in the SNS control and PNS decrease in injured individuals at the rest condition.…”

The Influence of Corticosteroids on Heart Rate Variablity in Acute Cervical Spinal Cord Injury

“…Analysis of HRV is a noninvasive and simple test to evaluate the autonomic nervous system function in patients with tetraplegia after SCI 16 . Linear analysis of 24-hour ECG recording was performed on the fi rst day of hospital admission after acute SCI.…”