Heart rate and blood pressure response improve the prediction of orthostatic cardiovascular dysregulation in persons with chronic spinal cord injury

Physiological Reports, 2020 · DOI: 10.14814/phy2.14617 · Published: January 1, 2020

Simple Explanation

This study investigates how blood pressure and heart rate respond to a sit-up test in people with chronic spinal cord injury (SCI). The researchers aimed to understand cardiovascular function in this group, as blood pressure instability after SCI is typically predicted by the severity and level of injury, rather than direct examination. The study found that many individuals with SCI experienced drops in blood pressure and significant increases in heart rate during the sit-up test, even if they didn't meet the standard definition of orthostatic hypotension. This suggests that the usual definition of orthostatic hypotension might not fully capture the extent of cardiovascular issues in people with SCI. By analyzing the patterns of heart rate and blood pressure changes, the researchers identified eight distinct response types, indicating varied autonomic responses to orthostatic stress. This suggests that a more detailed assessment of heart rate and blood pressure interactions is needed to diagnose cardiovascular dysregulation in individuals with SCI, rather than relying solely on injury level and severity.

Study Duration

2010 to 2018

Participants

159 individuals with SCI and 48 age-matched non-injured controls

Evidence Level

Not specified

Key Findings

1
Orthostatic hypotension occurred within each level and AIS classification of spinal cord injury, indicating it's not solely predictable by injury severity.
2
Many individuals with SCI experienced a drop in blood pressure accompanied by dramatic increases in heart rate, reflecting orthostatic intolerance beyond standard hypotension criteria.
3
Algorithmic cluster analysis of heart rate and blood pressure is more sensitive to diagnosing orthostatic cardiovascular dysregulation than traditional methods.

Research Summary

This study challenges the conventional method of predicting blood pressure instability after spinal cord injury (SCI) based solely on the neurological classification of SCI. It highlights that individuals with high-level and complete injuries are often anticipated to experience more frequent and severe blood pressure instability. The research demonstrates that the traditional definition of orthostatic hypotension, which relies on absolute decreases in blood pressure, is insufficient to characterize the complex blood pressure and heart rate responses during orthostatic stress in individuals with SCI. The study concludes that cardiovascular instability in SCI patients cannot be accurately predicted by the level and completeness of SCI alone. Both blood pressure and heart rate responses must be considered to fully characterize autonomic dysfunction following SCI.

Practical Implications

Improved Diagnosis

The study suggests that algorithmic cluster analysis of heart rate and blood pressure responses can improve the diagnosis of cardiovascular dysregulation in SCI patients.

Personalized Treatment

Recognizing the heterogeneity of cardiovascular responses in SCI patients is crucial for tailoring treatments to address individual needs.

Clinical Practice

The findings emphasize the need for clinicians to assess cardiovascular autonomic function beyond neurological classification in SCI patients.

Study Limitations

1
Did not consider beat-to-beat blood pressure or heart rate variability.
2
Prevalence of delayed orthostatic hypotension was evaluated in a subset of participants.
3
Did not evaluate the degree of the autonomic function using the ISAFSCI.

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