Assessing Heart Rate Variability As a Surrogate Measure of Cardiac Autonomic Function in Chronic Traumatic Spinal Cord Injury

Top Spinal Cord Inj Rehabil, 2015 · DOI: 10.1310/sci2101-28 · Published: January 1, 2015

Spinal Cord Injury Cardiovascular Science

Simple Explanation

The study investigates whether heart rate variability (HRV) differs based on the neurological level of impairment (NLI) and the American Spinal Cord Injury Association Impairment Scale (AIS) in individuals with chronic spinal cord injury (SCI). It also explores the relationship between low-frequency (LF) and high-frequency (HF) HRV measures. ECG data was collected on 56 subjects at rest. The HRV was analyzed using time and frequency domain measures. The results showed that there were no significant HRV differences across NLI and AIS subgroups. The study concludes that the utility of measuring LF:HF at rest in persons with chronic SCI is questionable. The relationship between LF and HF may not necessarily represent a rebalanced autonomic nervous system.

Study Duration

Not specified

Participants

56 subjects with chronic traumatic SCI

Evidence Level

Cross-sectional study

Key Findings

1
No significant differences in HRV measures were found across neurological level of impairment (NLI) and American Spinal Cord Injury Association Impairment Scale (AIS) subgroups.
2
A positive correlation was observed between low-frequency (LF) and high-frequency (HF) HRV indices in the entire sample and within impairment subgroups.
3
The LF:HF ratio may not be an appropriate marker to independently assess cardiac sympatho-vagal balance in individuals with chronic traumatic SCI at rest.

Research Summary

This study aimed to determine if there are differences in heart rate variability (HRV) measures across neurological level of impairment (NLI) and American Spinal Cord Injury Association Impairment Scale (AIS) subgroups, and to determine if there is a relationship between HRV frequency measures at rest. The study found no significant HRV differences across NLI and AIS subgroups, but a positive correlation between LF and HF indices was observed. The authors conclude that the LF:HF ratio may not be a suitable measure for assessing cardiac autonomic status at rest in individuals with chronic traumatic SCI.

Practical Implications

Re-evaluation of HRV Measures

The study suggests a need to re-evaluate the use of LF:HF ratio as a standalone measure of cardiac sympatho-vagal balance in chronic SCI.

Autonomic Subgrouping

The study implies that autonomic subgrouping based on the presence or absence of sympathetic skin response may be a more appropriate approach.

Comprehensive Autonomic Assessment

The study suggests a need for a comprehensive assessment of autonomic dysfunction, including orthostatic hypotension and autonomic dysreflexia.

Study Limitations

1
The sampling process was not ideal and may hinder generalizability.
2
The subgroups may have been too small to detect significant differences thus increasing the likelihood of a type II error.
3
Neurological impairment severity (NLI and AIS) does not accurately represent severity of autonomic dysfunction or autonomic completeness.

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