Background Due to sympathetic de-centralization, individuals with spinal cord injury (SCI), especially those with tetraplegia, often present with hypotension, worsened with upright posture. Several investigations in the non-SCI population have noted a relationship between chronic hypotension and deficits in memory, attention and processing speed and delayed reaction times. Objective To determine cognitive function in persons with SCI who were normotensive or hypotensive over a 24-h observation period while maintaining their routine activities. Methods Subjects included 20 individuals with chronic SCI (2–39 years), 13 with tetraplegia (C4–8) and 7 with paraplegia (T2–11). Individuals with hypotension were defined as having a mean 24-h systolic blood pressure (SBP) below 110 mmHg for males and 100 mmHg for females, and having spent ≥50% of the total time below these gender-specific thresholds. The cognitive battery used included assessment of memory (CVLT), attention and processing speed (Digit Span, Stroop word and color and Oral Trails A), language (COWAT) and executive function (Oral Trails B and Stroop color–word). Results Demographic parameters did not differ among the hypotensive and normotensive groups; the proportion of individuals with tetraplegia (82%) was higher in the hypotensive group. Memory was significantly impaired (P<0.05) and there was a trend toward slowed attention and processing speed (P<0.06) in the hypotensive compared to the normotensive group. Interpretation These preliminary data suggest that chronic hypotension in persons with SCI is associated with deficits in memory and possibly attention and processing speed, as previously reported in the non-SCI population.
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.
Asymptomatic hypotension relates to cognitive performance in persons with tetraplegia; therefore, BP normalization should be considered. The inappropriate cerebral vascular response to cognitive testing and poor test performance should be investigated in persons with paraplegia.
Objective: To describe the effect of spinal cord injury (SCI) on the QT variability index (QTVI). Methods: Digital electrocardiograms from 113 age-matched men (40 with tetraplegia, 26 with high paraplegia, 17 low paraplegia and 31 controls) were analyzed. RR interval, heart rate (HR) variability [total power (TPRR), low frequency (LFRR) and high frequency (HFRR)], QT interval duration, Bazett HR-corrected QT (QTc), QT interval variance (QTVN) and QTVI were compared. Results: Significant group main effects were present for RR, QTc, TPRR and LFRR, but not QT duration, QTVN or HFRR. Post hoc comparisons revealed the following: (1) longer RR in controls versus subjects with high paraplegia and low paraplegia, and in subjects with tetraplegia versus high paraplegia and low paraplegia; (2) QTc was longer in subjects with low paraplegia versus controls and shorter in subjects with tetraplegia versus high paraplegia, and (3) TPRR and LFRR were different in controls and subjects with high paraplegia compared to those with low paraplegia. QTVI was significantly elevated in all SCI groups compared to controls. Significant negative correlations between QTVI and HFRR were observed in all SCI groups, and TPRR and LFRR in subjects with tetraplegia and high paraplegia only. Age was negatively correlated in controls. Conclusions: QTVI is negatively affected in otherwise healthy SCI men compared to age-matched controls. This observation appears to reflect the attenuation of vagal modulation, sympathetic impairment above the sixth thoracic vertebra and/or a heightened degree of cardiovascular disease risk.
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