Assessment of autonomic function after acute spinal cord injury using heart rate variability analyses.
OBJECTIVE
Spinal cord injury (SCI) often results in severe dysfunction of the autonomic nervous system. C1-C8 SCI affects the supraspinal control to the heart, T1-T5 SCI affects the spinal sympathetic outflow to the heart, and T6-T12 SCI leaves sympathetic control to the heart intact. Heart rate variability (HRV) analysis can serve as a surrogate measure of autonomic regulation. The aim of this study was to investigate changes in HRV patterns and alterations in patients with acute traumatic SCI.


METHODS
As soon as possible after SCI patients who met the inclusion criteria had 24 h Holter monitoring of their cardiac rhythm, additional Holter monitoring were performed 1, 2, 3 and 4 weeks after SCI.


RESULTS
Fifty SCI patients were included. A significant increase in standard deviation of the average normal-to-normal (SDANN) sinus intervals was seen in the first month after injury (P=0.008). The increase was only significant in C1-T5 incomplete patients and in patients who did not experience one or more episodes of cardiac arrest. Significant lower values of Low Frequency Power, Total Power and the Low Frequency over High Frequency ratio were seen in the C1-T5 SCI patients compared with T6-T12 SCI patients.


CONCLUSIONS
The rise in SDANN in the incomplete C1-T5 patients could be due to spontaneous functional recovery caused by synaptic plasticity or remodelling of damaged axons. That the autonomic nervous system function differs between C1-C8, T1-T5 and T6-T12 patients suggest that the sympathovagal balance in both the C1-C8 and T1-T5 SCI patients has yet to be reached.
1] Department of Spinal Cord Injuries, Glostrup hospital/Rigshospitalet 2081, Copenhagen, Denmark [2] Department of Clinical Neurophysiology, Rigshopitalet, Copenhagen, Denmark.
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L
Malmqvist
1] Department of Spinal Cord Injuries, Glostrup hospital/Rigshospitalet 2081, Copenhagen, Denmark [2] Faculty of Medical and Health Sciences, University of Copenhagen, Copenhagen, Denmark [3] Department of Cardiology, Gentofte Hospital, Copenhagen, Denmark.
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T
Biering-Sørensen
Department of Spinal Cord Injuries, Glostrup hospital/Rigshospitalet 2081, Copenhagen, Denmark.
K
K
Bartholdy
Department of Medicine, Div. Phys.Med. & Rehab., ICORD, Vancouver, British Columbia and Spinal Cord Program, GF Strong Rehabilitation Centre, University of British Columbia, Vancouver, British Columbia, Canada.
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A
Krassioukov
Department of Neuroanesthesiology, Rigshospitalet, Copenhagen, Denmark.
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KL
Welling
1] Faculty of Medical and Health Sciences, University of Copenhagen, Copenhagen, Denmark [2] Department of Cardiology, Rigshospitalet, Copenhagen, Denmark.
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JH
Svendsen
Spine Section, Department of Orthopedic Surgery, Rigshospitalet, Copenhagen, Denmark.
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A
Kruse
Department of Spinal Cord Injuries, Glostrup hospital/Rigshospitalet 2081, Copenhagen, Denmark.
B
B
Hansen
1] Department of Spinal Cord Injuries, Glostrup hospital/Rigshospitalet 2081, Copenhagen, Denmark [2] Faculty of Medical and Health Sciences, University of Copenhagen, Copenhagen, Denmark.
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F
Biering-Sørensen
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001342:Autonomic Nervous System Diseases / Q000175:diagnosis / Q000209:etiology*; D002574:Cervical Vertebrae / Q000473:pathology; D003718:Denmark; D005260:Female; D005583:Fourier Analysis; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D016014:Linear Models; D008159:Lumbar Vertebrae / Q000473:pathology; D008297:Male; D008875:Middle Aged; D013119:Spinal Cord Injuries / Q000145:classification / Q000150:complications*; D013904:Thoracic Vertebrae / Q000473:pathology; D013997:Time Factors; D055815:Young Adult