Comparison of 24-hour cardiovascular and autonomic function in paraplegia, tetraplegia, and control groups: Implications for cardiovascular risk

Abstract

Background: Fluctuations in 24-hour cardiovascular hemodynamics, specifically heart rate (HR) and blood pressure (BP), are thought to reflect autonomic nervous system (ANS) activity. Persons with spinal cord injury (SCI) represent a model of ANS dysfunction, which may affect 24-hour hemodynamics and predispose these individuals to increased cardiovascular disease risk. Objective: To determine 24-hour cardiovascular and ANS function among individuals with tetraplegia (n = 20; TETRA: C4-C8), high paraplegia (n = 10; HP: T2-T5), low paraplegia (n = 9; LP: T7-T12), and non-SCI controls (n = 10). Twenty-four-hour ANS function was assessed by time domain parameters of heart rate variability (HRV); the standard deviation of the 5-minute average R-R intervals (SDANN; milliseconds/ms), and the root-mean square of the standard deviation of the R-R intervals (rMSSD; ms). Subjects wore 24-hour ambulatory monitors to record HR, HRV, and BP. Mixed analysis of variance (ANOVA) revealed significantly lower 24-hour BP in the tetraplegic group; however, BP did not differ between the HP, LP, and control groups. Mixed ANOVA suggested significantly elevated 24-hour HR in the HP and LP groups compared to the TETRA and control groups (P < 0.05); daytime HR was higher in both paraplegic groups compared to the TETRA and control groups (P < 0.01) and nighttime HR was significantly elevated in the LP group compared to the TETRA and control groups (P < 0.01). Twenty-four-hour SDANN was significantly increased in the HP group compared to the LP and TETRA groups (P < 0.05) and rMSSD was significantly lower in the LP compared to the other three groups (P < 0.05). Elevated 24-hour HR in persons with paraplegia, in concert with altered HRV dynamics, may impart significant adverse cardiovascular consequences, which are currently unappreciated.

Heart rate variability in individuals with thoracic spinal cord injury

“…The first is that the results of previous studies that tried to establish differences between high-and low-level paraplegia did not find significant differences between levels. [13][14][15] This concurs with the results obtained from one of our secondary analyses. The other reason is because differences in HRV are not always due to altered or preserved autonomic function, but can be due to long-term use of a wheelchair and/or the lifestyle adopted.…”

“…15 The RMSSD estimates the short-term components of the HRV and is considered an indirect measure of the vagal cardiac tone.…”

“…3,[6][7][8][9][10][11][12][13][14][15][16] Although participants with high-level SCI, primarily cervical injuries, present with altered cardiac autonomic control, 6,7 some studies have analyzed the HRV of patients with SCI without considering the level of injury (that is, thoracic or cervical). 9 As previously reported, cardiac autonomic control can be impaired due to immobility resulting from injury and the sedentary lifestyle adopted after injury.…”

“…9 As previously reported, cardiac autonomic control can be impaired due to immobility resulting from injury and the sedentary lifestyle adopted after injury. For this reason, in contrast with the classifications of other studies, 3,14,15 our study explores HRV only in patients with thoracic SCI because these patients have a similar level of daily activity and use a manual wheelchair, which is enabled by preserved motor function in their upper limbs.…”

Orthostatic responses to anticholinesterase inhibition in spinal cord injury

“…We reported that the prevalence of hypotension recorded in the medical record was 39%, 21 and documented hypotension over the course of a typical 24-hour day in 70% of subjects with tetraplegia. 22 However, we found that the diagnosis of hypotension was less than 1% and treatment with prescription anti-hypotensive agents was negligible (3 of 1291 records: 0.2%) in veterans with tetraplegia. 21 These findings most likely reflect the limited number of FDA approved agents available to treat hypotension and OH and a paucity of data supporting the safe and effective use of these medications in the SCI population.…”