Influence of the neurological level of spinal cord injury on cardiovascular outcomes in humans: a meta-analysis

Ergogenic effects of spinal cord stimulation on exercise performance following spinal cord injury

Cervical or upper-thoracic spinal cord injury (SCI, ≥T6) often leads to low resting blood pressure (BP) and impaired cardiovascular responses to acute exercise due to disrupted supraspinal sympathetic drive. Epidural spinal cord stimulation (invasive, ESCS) and transcutaneous spinal cord stimulation (non-invasive, TSCS) have previously been used to target dormant sympathetic circuits and modulate cardiovascular responses. This case series compared the effects of cardiovascular-optimised ESCS and TSCS versus sham ESCS and TSCS on modulating cardiovascular responses and improving submaximal upper-body exercise performance in individuals with SCI. Seven males with a chronic, motor-complete SCI between C6 and T4 underwent a mapping session to identify cardiovascular responses to spinal cord stimulation. Subsequently, four participants (two ESCS and two TSCS) completed submaximal exercise testing. Stimulation parameters (waveform, frequency, intensity, epidural electrode array configuration, and transcutaneous electrode locations in the lumbosacral region) were optimised to elevate cardiovascular responses (CV-SCS). A sham condition (SHAM-SCS) served as a comparison. Participants performed arm-crank exercise to exhaustion at a fixed workload corresponding to above ventilatory threshold, on separate days, with CV-SCS or SHAM-SCS. At rest, CV-SCS increased BP and predicted left ventricular cardiac contractility and total peripheral resistance. During exercise, CV-SCS increased time to exhaustion and peak oxygen pulse (a surrogate for stroke volume), relative to SHAM-SCS. Ratings of perceived exertion also tended to be lower with CV-SCS than SHAM-SCS. Comparable improvements in time to exhaustion with ESCS and TSCS suggest that both approaches could be promising ergogenic aids to support exercise performance or rehabilitation, along with reducing fatigue during activities of daily living in individuals with SCI.

Initial Heart Rate Predicts Functional Independence in Patients With Spinal Cord Injury Requiring Surgery: A Registry-Based Study in a Mature Trauma System Over the Past 10 Years

STUDY DESIGN

Retrospective Cohort Study.

OBJECTIVES

To determine the ability of early vital sign abnormalities to predict functional independence in patients with SCI that required surgery.

METHODS

A retrospective analysis of data extracted from the Pennsylvania Trauma Outcome Study database. Inclusion criteria were patients >18 years with a diagnosis of SCI who required urgent spine surgery in Pennsylvania from 1/1/2010-12/31/2020 and had complete records available.

RESULTS

A total of 644 patients met the inclusion criteria. The mean age was 47.1 ± 14.9 years old and the mean injury severity score (ISS) was 22.3 ± 12.7 with the SCI occurring in the cervical, thoracic, and lumbar spine in 61.8%, 19.6% and 18.0%, respectively. Multivariable logistic regression analyses for predictors of functional independence at discharge showed that higher HR at the scene (OR 1.016, 95% CI 1.006-1.027, P = .002) and lower ISS score (OR .894, 95% CI .870-.920, P < .001) were significant predictors of functional independence. Similarly, higher admission HR (OR 1.015, 95% CI 1.004-1.027, P = .008) and lower ISS score (OR .880, 95% CI 0.864-.914, P < .001) were significant predictors of functional independence. Peak Youden indices showed that patients with HR at scene >70 and admission HR ≥83 were more likely to achieve functional independence.

CONCLUSIONS

Early heart rate is a strong predictor of functional independence in patients with SCI. HR at scene >70 and admission HR ≥83 is associated with improved outcomes, suggesting lack of neurogenic shock.

Sex differences in heart disease prevalence among individuals with spinal cord injury: A population-based study

CONTEXT/OBJECTIVE

The risk for cardiovascular disease is amplified following spinal cord injury, but whether risk differs between the sexes remains unknown. Here, we evaluated sex differences in the prevalence of heart disease among individuals with spinal cord injury, and compared sex differences with able-bodied individuals.

DESIGN

The design was a cross-sectional study. Multivariable logistic regression analysis was conducted, using inverse probability weighting to account for the sampling method and to adjust for confounders.

SETTING

Canada.

PARTICIPANTS

Individuals who participated in the national Canadian Community Health Survey.

INTERVENTIONS

Not applicable.

OUTCOME MEASURES

Self-reported heart disease.

RESULTS

Among 354 individuals with spinal cord injury, the weighted prevalence of self-reported heart disease was 22.9% in males and 8.7% in females, with an inverse-probability weighted odds ratio of 3.44 (95% CI 1.70-6.95) for males versus females. Among 60,605 able-bodied individuals, the prevalence of self-reported heart disease was 5.8% in males and 4.0% in females, with an inverse probability weighted odds ratio of 1.62 (95% CI 1.50-1.75) for males versus females. The effect of male sex on increasing heart disease prevalence was about two times higher among individuals with spinal cord injury than able-bodied individuals (relative difference in inverse probability weighted odds ratios = 2.12, 95% CI 1.08-4.51).

CONCLUSION

Males with spinal cord injury exhibit a significantly higher prevalence of heart disease, compared with females with spinal cord injury. Moreover, relative to able-bodied individuals, spinal cord injury amplifies sex-related differences in heart disease. Overall, this work will inform targeted cardiovascular prevention strategies, and may also inform a better understanding of cardiovascular disease progression in both able-bodied and individuals with spinal cord injury.

Diurnal variation of heart rate variability in individuals with spinal cord injury

BACKGROUND

Heart rate variability (HRV) may provide objective information about cardiogenic autonomic balance in individuals with spinal cord injury (SCI). The aim of this study was to characterize the diurnal variation of HRV in individuals with SCI at lesion level T6 and above and lesion level below T6.

METHODS

This was a retrospective analysis of a prior cross-sectional study. Individuals with chronic SCI underwent 24 h recording of the time between consecutive R waves (RR interval) to derive parameters of HRV as follows: standard deviation of all normal-to-normal R-R intervals (SDNN) and square root of the mean of the squared differences between successive R-R intervals (RMSSD) (time domain); and high frequency power (HF), low-frequency power (LF), very low frequency power (VLF), ultra-low frequency power (ULF) and total power (TP) (frequency domain). Changes in the magnitude of HRV outcomes over the 24 h period were investigated using a novel multi-component cosinor model constrained to the form of a three-harmonic Fourier series.

RESULTS

Participants were grouped as lesion level T6 and above (n = 22) or below T6 (n = 36). Most of them were male (n = 40, 69%) and the median age (interquartile range) was 50.5 (28) years. Both groups exhibited similar diurnal patterns in most HRV metrics. The lowest values occurred in the late afternoon (4-6 pm) and gradually increased, peaking around midnight to early morning (1-6 am). Exceptions included RMSSD, which peaked before midnight, and ULF, which showed a double peak pattern that peaked from 11 am to 1 pm and 4-6 am in participants with lesion level at T6 and above. The HRV values in participants with lesion level T6 and above were generally lower than participants with lesion level below T6, except for peak values of RMSSD, HF and LF.

CONCLUSION

This study demonstrated substantial diurnal variation of HRV in participants with SCI in both groups of participants. In clinical and research settings, diurnal variations in HRV must be taken into consideration.

Reliability of five-minute vs. one-hour heart rate variability metrics in individuals with spinal cord injury

Background

A previous study showed low reliability of 1-h HRV outcomes in participants with spinal cord injury (SCI), but it was not certain whether the low reliability was due to the unrestricted activity of participants. We aimed to investigate test-retest reliability of HRV metrics in individuals with SCI using a 1-h measurement in a supine position.

Methods

Individuals with SCI underwent two sessions of 1-h recording of the time between consecutive R waves (RR-intervals) in a supine position. HRV outcomes were obtained from a single 5-min data segment and for the full 1-h recording. HRV parameters of interest were: standard deviation of all normal-to-normal R-R intervals (SDNN) and square root of the mean of the squared differences between successive R-R intervals (RMSSD) (time domain); and high frequency power (HF), low frequency power (LF), very low frequency power (VLF), ultra-low frequency power (ULF) and total power (TP) (frequency domain). Relative reliability was assessed by intraclass correlation coefficient (ICC). Absolute reliability was assessed by coefficient of variation (CV) and Bland-Altman limits of agreement (LoA).

Results

Data from 37 individuals (14 with tetraplegia and 23 with paraplegia) were included. Relative reliability was higher for the 1-h (ICCs ranged from 0.13-0.71) than for the 5-min duration (ICCs ranged from 0.06-0.50) in the overall SCI group for all HRV metrics. Participants with tetraplegia had lower relative reliability compared to participants with paraplegia in all HRV metrics for the 5-min duration (ICCs ranged from -0.01-0.34 vs. 0.21-0.57). For the 1-h duration, participants with paraplegia showed higher relative reliability than participants with tetraplegia in all HRV metrics (ICCs ranged from 0.18-0.79 vs. 0.07-0.54) except TP (ICC 0.69 vs. 0.82). In terms of absolute reliability, the CVs and LoAs for the 1-h duration were better than for the 5-min duration. In general, time domain metrics showed better reliability than frequency domain metrics for both durations in participants with tetraplegia and paraplegia. The lowest CV and narrowest 95% LoA were found for SDNN in 5-min and 1-h durations overall and in both lesion levels.

Conclusions

The supine position did not provide better reliability compared to unrestricted activity in participants with SCI. HRV analysis using a 5-min duration is of limited value in SCI due to poor reliability. For the 1-h analysis duration, interpretation of the reliability of HRV varies according to lesion level: it is recommended to take lesion level into account when interpreting reliability measures.

Item Banks for Measuring the Effect of Blood Pressure Dysregulation on Health-Related Quality of Life in Persons With Spinal Cord Injury

OBJECTIVE

To report on the development and calibration of the new Blood Pressure Dysregulation Measurement System (BPD-MS) item banks that assess the effect of BPD on health-related quality of life (HRQOL) and the daily activities of Veterans and non-Veterans with spinal cord injury (SCI).

DESIGN

Cross-sectional survey study.

SETTING

Two Veteran Affairs medical centers and a SCI model system site.

PARTICIPANTS

454 respondents with SCI (n=262 American Veterans and n=192 non-Veterans; N=454).

INTERVENTIONS

Not applicable MAIN OUTCOME MEASURES: The BPD-MS item banks.

RESULTS

BPD item pools were developed and refined using literature reviews, qualitative data from focus groups, and cognitive debriefing of persons with SCI and professional caregivers. The item banks then underwent expert review, reading level assessment, and translatability review prior to field testing. The items pools consisted of 180 unique questions (items). Exploratory and confirmatory factor analyses, item response theory modeling, and differential item function investigations resulted in item banks that included a total of 150 items: 75 describing the effect of autonomic dysreflexia on HRQOL, 55 describing the effect of low blood pressure (LBP) on HRQOL, and 20 describing the effect of LBP on daily activities. In addition, 10-item short forms were constructed based on item response theory-derived item information values and the clinical relevance of item content.

CONCLUSIONS

The new BPD-MS item banks and corresponding 10-item short forms were developed using established rigorous measurement development standards, which represents the first BPD-specific patient-reported outcomes measurement system unique for use in the SCI population.

Relationships between cardiovascular disease risk, neuropathic pain, mental health, and autonomic function in chronic spinal cord injury

STUDY DESIGN

Multicentre, cross-sectional study.

OBJECTIVES

To determine if clinical measures of poor mental health (MH-) and neuropathic pain (NP) are related to increased CVD risk in individuals with chronic spinal cord injury (SCI), and further elucidate the relationships between CVD risk, autonomic function, NP, and MH-.

SETTING

Eight SCI rehabilitation centres in the Netherlands.

METHODS

Individuals (n = 257) with a traumatic, chronic (≥10 yrs) SCI, with age at injury between 18-35 years, completed a self-report questionnaire and a one-day visit to a rehabilitation centre for testing. CVD risk was calculated using Framingham risk score. NP was inferred using The Douleur Neuropathique 4 clinical examination, and MH- was assessed using the five-item Mental Health Inventory questionnaire. Cardiovascular autonomic function was determined from peak heart rate during maximal exercise (HRpeak).

RESULTS

There was a high prevalence of both NP (39%) and MH- (45%) following SCI. MH- was significantly correlated with an adverse CVD risk profile (r = 0.174; p = 0.01), increased the odds of adverse 30-year CVD risk by 2.2 (CI 0.92-2.81, p = 0.02), and is an important variable in determining CVD risk (importance=0.74, p = 0.05). Females (p = 0.05) and those with a higher HRpeak (p = 0.046) tended to be more likely to have NP.

CONCLUSIONS

Clinical measures of MH-, but not NP, are important factors for increased CVD risk following SCI. NP tended to be more prevalent in those with more preserved cardiovascular autonomic function. The interrelationships between secondary consequences of SCI are complex and need further exploration.

Effects of C2 hemisection on respiratory and cardiovascular functions in rats

High cervical spinal cord injuries induce permanent neuromotor and autonomic deficits. These injuries impact both central respiratory and cardiovascular functions through modulation of the sympathetic nervous system. So far, cardiovascular studies have focused on models of complete contusion or transection at the lower cervical and thoracic levels and diaphragm activity evaluations using invasive methods. The present study aimed to evaluate the impact of C2 hemisection on different parameters representing vital functions (i.e., respiratory function, cardiovascular, and renal filtration parameters) at the moment of injury and 7 days post-injury in rats. No ventilatory parameters evaluated by plethysmography were impacted during quiet breathing after 7 days post-injury, whereas permanent diaphragm hemiplegia was observed by ultrasound and confirmed by diaphragmatic electromyography in anesthetized rats. Interestingly, the mean arterial pressure was reduced immediately after C2 hemisection, with complete compensation at 7 days post-injury. Renal filtration was unaffected at 7 days post-injury; however, remnant systolic dysfunction characterized by a reduced left ventricular ejection fraction persisted at 7 days post-injury. Taken together, these results demonstrated that following C2 hemisection, diaphragm activity and systolic function are impacted up to 7 days post-injury, whereas the respiratory and cardiovascular systems display vast adaptation to maintain ventilatory parameters and blood pressure homeostasis, with the latter likely sustained by the remaining descending sympathetic inputs spared by the initial injury. A better broad characterization of the physiopathology of high cervical spinal cord injuries covering a longer time period post-injury could be beneficial for understanding evaluations of putative therapeutics to further increase cardiorespiratory recovery.

Is it Feasible to Use a Low-Cost Wearable Sensor for Heart Rate Monitoring within an Upper Limb Training in Spinal Cord Injured Patients?: A Pilot Study

(1) Background: Cervical spinal cord injury (SCI) patients have impairment in the autonomic nervous system, reflected in the cardiovascular adaption level during the performance of upper limb (UL) activities carried out in the rehabilitation process. This adaption level could be measured from the heart rate (HR) by means of wearable technologies. Therefore, the objective was to analyze the feasibility of using Xiaomi Mi Band 5 wristband (XMB5) for HR monitoring in these patients during the performance of UL activities; (2) Methods: The HR measurements obtained from XMB5 were compared to those obtained by the professional medical equipment Nonin LifeSense II capnograph and pulse oximeter (NLII) in static and dynamic conditions. Then, four healthy people and four cervical SCI patients performed a UL training based on six experimental sessions; (3) Results: the correlation between the HR measurements from XMB5 and NLII devices was strong and positive in healthy people (r = 0.921 and r = 0.941 (p < 0.01) in the static and dynamic conditions, respectively). Then, XMB5 was used within the experimental sessions, and the HR oscillation range measured was significantly higher in healthy individuals than in patients; (4) Conclusions: The XMB5 seems to be feasible for measuring the HR in this biomedical application in SCI patients.

Vital sign differences between septic patients with tetraplegia and paraplegia

STUDY DESIGN

Retrospective chart review.

OBJECTIVES

Sepsis is a leading preventable cause of death in patients with chronic spinal cord injury (SCI). Individuals with tetraplegia may exhibit different signs and symptoms of infection compared to those with paraplegia. In this study, we examine differences in vital signs (VS) and mental status between septic patients with tetraplegia and paraplegia with the goal of improving early identification of sepsis in this population.

SETTING

Veterans hospital in Washington, USA.

METHODS

Participants consisted of 19 patients with tetraplegia and 16 with paraplegia who were transferred from an SCI Service to a higher level of care with sepsis between June 1, 2010 and June 1, 2018 (n = 35). We compared VS between patients with tetraplegia and paraplegia at baseline and during sepsis including temperature, heart rate (HR), and blood pressure as well as presence/absence of altered mental status (AMS).

RESULTS

While there were no significant VS differences between groups at baseline, septic patients with tetraplegia had lower maximum temperature (38.2 °C versus 39.2 °C, p = 0.003), lower maximum HR (106 versus 124 beats/minute, p = 0.004), and more frequent AMS compared to septic patients with paraplegia (79% versus 31%, p = 0.007).

CONCLUSION

Patients with tetraplegia may not be able to mount fever and tachycardia to the same degree as patients with paraplegia and may be more prone to developing AMS during sepsis. These findings suggest that changes to VS parameter cut-offs may improve sensitivity and be useful in identifying sepsis earlier in the tetraplegic population.

The susceptibility of cardiac arrhythmias after spinal cord crush injury in rats

High-level spinal cord injury (SCI) often interrupts supraspinal regulation of sympathetic input to the heart. Although it is known that dysregulated autonomic control increases the risk for cardiac disorders, the mechanisms mediating SCI-induced arrhythmias are poorly understood. Here, we employed a rat model of complete spinal cord crush injury at the 2nd/3rd thoracic (T2/3) level to investigate cardiac rhythm disorders resulting from SCI. Rats with T9 injury and naïve animals served as two controls. Four weeks after SCI, rats were implanted with a radio-telemetric device for electrocardiogram and blood pressure monitoring. During 24-h recordings, heart rate variability in rats with T2/3 but not T9 injury exhibited a significant reduction in the time domain, and a decrease in power at low frequency but increased power at high frequency in the frequency domain which indicates reduced sympathetic and increased parasympathetic outflow to the heart. Pharmacological blockade of the sympathetic or parasympathetic branches confirmed the imbalance of cardiac autonomic control. Activation of sympatho-vagal input during the induction of autonomic dysreflexia by colorectal distention triggered various severe arrhythmic events in T2/3 injured rats. Meanwhile, intravenous infusion of the β1-adrenergic receptor agonist, dobutamine, caused greater incidence of arrhythmias in rats with T2/3 injury than naïve and T9 injured controls. Together, the results indicate that high-level SCI increases the susceptibility to developing cardiac arrhythmias likely owing to compromised autonomic homeostasis. The T2/3 crush model is appropriate for studying abnormal cardiac electrophysiology resulting from SCI.

Accidental boosting in an individual with tetraplegia - considerations for the interpretation of cardiopulmonary exercise testing

CONTEXT

Autonomic dysreflexia (AD), characterized by a transient increase in systolic blood pressure (BP), is experienced by individuals with spinal cord injury (SCI) and can be purposefully induced ('boosting') to counteract autonomic dysfunction that impairs cardiovascular responses to exercise. Herein, we demonstrate the impact of unintentional boosting observed during cardiopulmonary exercise testing (CPET) in an inactive male with SCI (C5, motor-complete).

FINDINGS

On two separate occasions the individual performed a standard arm-crank CPET (1-min stages, 7W increase in resistance) following by a longer CPET (4-min stages, 12W increase in resistance), both to volitional exhaustion. The second CPET was performed to confirm the accuracy of exercise intensity prescription and verify peak exercise parameters. Immediately following the second CPET on the initial visit, the individual reported symptoms of AD, verified as a 58mmHg increase in systolic BP from baseline. Relative to the first CPET, performed only 35 min earlier, there were pronounced differences in peak exercise responses. In comparison to the longer CPET performed on the second visit without a concomitant episode of AD (thereby controlling for the type of CPET protocol administered), peak exercise outcomes were considerably elevated: power output (Δ19W), oxygen uptake (Δ3.61 ml·kg·^-1min^-1), ventilation (Δ11.4 L ·min^-1) and heart rate (Δ9 b·min^-1).

CONCLUSION/CLINICAL RELEVANCE

This case raises important considerations around the nuances of CPET in this population. In individuals susceptible to BP instability, the physiologically boosted state may explain a significant proportion of the variance in peak aerobic capacity and should be closely monitored before and after clinical CPET.

Trends in the presentation and management of traumatic spinal cord lesions above T6: 20-Year experience in a tertiary-level hospital in Spain

OBJECTIVE

To analyze the changes in demographic and lesion characteristics of persons with acute traumatic spinal cord injury (ATSCI) above T6 over a period of 20 years, and to evaluate their impact on ICU resources use, length of stay and mortality.

DESIGN

Retrospective observational study.

SETTING

Intensive Care Unit (ICU) of the University Hospital Complex of A Coruña, Spain.

PARTICIPANTS

The study included 241 persons between 1998 and 2017 with an ATSCI above T6. For the purposes of the analysis, the overall study period was divided into three subperiods.

RESULTS

Both the mean age of the people with ATSCI (49 vs. 51 vs. 57 years; P = 0.046) and the Charlson Comorbidity Index were higher during the last subperiod (mean: 1.9 ± 2.2; P &lt; 0.01). The most frequent cause of the injury was falls, whose percentage increased over the years. The most common classification in the American Spinal Injury Association Impairment scale was grade A. An increase in the score of the Acute Physiology and Chronic Health Evaluation (APACHE II) score was observed (median: 9 vs. 10 vs. 15; P &lt; 0.01). The length of stay in the ICU has decreased significantly over the years (30 ± 19 vs. 22 ± 14 vs. 19 ± 13 days). No significant differences were found between the rates of ICU or in-hospital mortality recorded over the three subperiods.

CONCLUSIONS

Despite the progressive increase in the age, comorbidity, and APACHE II, the length of ICU stay decreased significantly, with no associated changes in the mortality rates.

Impact of Rehabilitation Nutrition and Healthy Weight Maintenance in Motor-Complete Tetraplegia Patients

Cachexia and low muscle mass in motor-complete tetraplegia are associated with poor outcomes. This study aimed to document anthropometric, body composition, and nutritional indices in patients and to assess the effect of a comprehensive rehabilitation nutrition program in cachexia and low muscle mass. For 34 motor-complete tetraplegia in the subacute phase, a comprehensive rehabilitation nutrition program was provided for 8 to 9 weeks. Risk of malnutrition, anthropometric and body composition indices, as well as laboratory tests were assessed upon admission and at discharge. A body mass index of less than 20.2 kg/m2 was used as the cut-off value for obesity. Upon admission, 73.5% of patients were classified as obese, half were at risk of malnutrition, and 29.4% were compatible with cachexia. Compared to the premorbid state, the non-obese group showed greater weight reduction (p < 0.01) and higher prevalence of low muscle mass (p = 0.004) than the obese group. Disease duration was different between groups (p < 0.01). After rehabilitation, malnutrition risk, protein levels, and hemodynamic results improved in both groups (p < 0.05). A significant time × group interaction was observed for muscle mass, skeletal muscle mass, and appendicular lean mass index (p < 0.05). Muscle mass was maintained while fat components increased in both groups. Functional improvement was negatively correlated with an increase in fat components (p < 0.05). A personalized rehabilitation nutrition intervention improved the nutritional status, body composition, and functional outcomes in motor-complete tetraplegia. The increase in muscle mass was associated with functional gain; healthy weight gain or maintenance may improve the level of independence. Further studies to endorse this beneficial evidence of rehabilitation nutrition in the maintenance of muscle component are needed.

Influence of respiratory loading on left-ventricular function in cervical spinal cord injury

KEY POINTS

Cervical spinal cord injury (C-SCI) alters both the cardiac and respiratory systems, however little is known as to how these systems interact following injury. Here, we manipulated inspiratory or expiratory intrathoracic pressure (ITP) to mechanistically test the role of the respiratory pump on circulatory function in highly-trained individuals with C-SCI and an able-bodied reference group. In individuals with C-SCI, greater ITP during expiratory loading caused dynamic hyperinflation that was associated with impaired left-ventricular filling. More negative ITP during inspiratory loading did not significantly alter left-ventricular volumes in either group. Interventions that prevent dynamic hyperinflation and/or enhance the ability to generate expiratory pressures may help preserve left-ventricular filling in individuals with C-SCI.

ABSTRACT

Cervical spinal cord injury (C-SCI) negatively impacts cardiac and respiratory function. As the heart and lungs are linked via the pulmonary circuit these systems are interdependent. Here, we utilized inspiratory and expiratory loading to assess whether augmenting the respiratory pump improves left-ventricular (LV) filling and output in individuals with motor-complete C-SCI. We hypothesized LV end-diastolic volume (LVEDV) would increase and decrease with inspiratory and expiratory loading, respectively. Participants (C-SCI: 7M/1F, 35±7 years; able-bodied: 7M/1F, 32±6 years) were assessed under five conditions during 45° head-up tilt; unloaded, inspiratory loading with -10 and -20cmH₂ O esophageal pressure (Pes) on inspiration, and expiratory loading with +10 and +20cmH₂ O Pes on expiration. An esophageal balloon catheter monitored Pes and LV structure and function were assessed by echocardiography. In C-SCI only, (1) +20cmH₂ O reduced LVEDV vs. unloaded (81±15 vs. 88±11 mL, p = 0.006); (2) heart rate was higher during +20cmH₂ O compared to unloaded (p = 0.001) and +10cmH₂ O (p = 0.002); (3) cardiac output was higher during +20cmH₂ O than unloaded (p = 0.002); and (4) end-expiratory lung volume was higher during +20cmH₂ O vs. unloaded (63±10 vs. 55±13% total lung capacity, p = 0.003) but was unaffected by inspiratory loading. In both groups, -10 and -20cmH₂ O had no significant effect on LVEDV. These findings suggest greater expiratory positive pressure acutely impairs LV filling in C-SCI, potentially via impaired venous return, mediastinal constraint and/or direct ventricular interaction subsequent to dynamic hyperinflation. Inspiratory loading did not significantly improve LV function in C-SCI and neither inspiratory nor expiratory loading affected cardiac function or lung volumes in able-bodied participants. Abstract figure legend Background: Cervical spinal cord injury (C-SCI) alters both the cardiac and respiratory systems. However, expiratory function is compromised to a greater extent than inspiratory function. Experimental set up: To examine how the cardiac and respiratory systems interact following C-SCI we manipulated inspiratory or expiratory intrathoracic pressure (ITP) to mechanistically test how changes in ITP and lung volumes influence cardiac function in highly-trained individuals with C-SCI and an able-bodied reference group. Participants were assessed under five conditions during 45° head-up tilt; unloaded, two inspiratory loading, and two expiratory loading conditions.

KEY FINDINGS

Following C-SCI, greater ITP during expiratory loading increased lung volumes and was associated with impaired left-ventricular filling. Interventions that prevent increases in lung volumes and/or enhance the ability to generate expiratory pressures may help preserve left-ventricular filling in individuals with C-SCI. A portion of this figure was created with biorender.com This article is protected by copyright. All rights reserved.

Effects of transcutaneous spinal stimulation on spatiotemporal cortical activation patterns: A proof-of-concept EEG study

OBJECTIVE

Transcutaneous spinal cord stimulation (TSS) has been shown to be a promising non-invasive alternative to epidural spinal cord stimulation (ESS) for improving outcomes of people with spinal cord injury (SCI). However, studies on the effects of TSS on cortical activation are limited. Our objectives were to evaluate the spatiotemporal effects of TSS on brain activity, and determine changes in functional connectivity under several different stimulation conditions. As a control, we also assessed the effects of functional electrical stimulation (FES) on cortical activity.

APPROACH

Non-invasive scalp electroencephalography (EEG) was recorded during TSS or FES while five neurologically intact participants performed one of three lower-limb tasks while in the supine position: (1) A no contraction control task, (2) a rhythmic contraction task, or (3) a tonic contraction task. After EEG denoising and segmentation, independent components were clustered across subjects to characterize sensorimotor networks in the time and frequency domains. Independent components of the event related potentials (ERPs) were calculated for each cluster and condition. Next, a Generalized Partial Directed Coherence (gPDC) analysis was performed on each cluster to compare the functional connectivity between conditions and tasks.

RESULTS

Independent Component analysis of EEG during TSS resulted in three clusters identified at Brodmann areas (BA) 9, BA 6, and BA 4, which are areas associated with working memory, planning, and movement control. Lastly, we found significant (p < 0.05, adjusted for multiple comparisons) increases and decreases in functional connectivity of clusters during TSS, but not during FES when compared to the no stimulation conditions.

SIGNIFICANCE

The findings from this study provide evidence of how TSS recruits cortical networks during tonic and rhythmic lower limb movements. These results have implications for the development of spinal cord-based computer interfaces, and the design of neural stimulation devices for the treatment of pain and sensorimotor deficit.

Heart rate changes associated with autonomic dysreflexia in daily life of individuals with chronic spinal cord injury

STUDY DESIGN

Secondary data analysis.

OBJECTIVE

To characterize heart rate (HR) changes during autonomic dysreflexia (AD) in daily life for individuals with chronic spinal cord injury (SCI).

SETTING

University-based laboratory/community-based outpatient.

METHODS

Cardiovascular data, previously collected during a 24-h ambulatory surveillance period in individuals with chronic SCI, were assessed. Any systolic blood pressure (SBP) increase ≥20 mmHg from baseline was identified and categorized into confirmed AD (i.e., diarized trigger), unknown (i.e., no diary entry), or unlikely AD (i.e., potential exertion driven SBP increase) groups. SBP-associated HR changes were categorized as unchanged, increased or decreased compared to baseline.

RESULTS

Forty-five individuals [8 females, median age and time since injury of 43 years (lower and upper quartiles 36-50) and 17 years (6-23), respectively], were included for analysis. Overall, 797 episodes of SBP increase above AD threshold were identified and classified as confirmed (n = 250, 31.4%), unknown (n = 472, 59.2%) or unlikely (n = 75, 9.4%). The median number of episodes per individual within the 24-h period was 13 (8-28). HR-decrease/increase ratio was 3:1 for confirmed and unknown, and 1.5:1 for unlikely episodes. HR changes resulting in brady-/tachycardia were 34.4%/2.8% for confirmed, 39.6%/3.4% unknown, and 26.7%/9.3% for unlikely episodes, respectively.

CONCLUSIONS

Our findings suggest that the majority of confirmed AD episodes are associated with a HR decrease. Using wearable-sensors-derived measures of physical activity in future studies could provide a more detailed characterization of HR changes during AD and improve AD identification.

Evaluation of the Cardiometabolic Disorders after Spinal Cord Injury in Mice

Changes in cardiometabolic functions contribute to increased morbidity and mortality after chronic spinal cord injury. Despite many advancements in discovering SCI-induced pathologies, the cardiometabolic risks and divergences in severity-related responses have yet to be elucidated. Here, we examined the effects of SCI severity on functional recovery and cardiometabolic functions following moderate (50 kdyn) and severe (75 kdyn) contusions in the thoracic-8 (T8) vertebrae in mice using imaging, morphometric, and molecular analyses. Both severities reduced hindlimbs motor functions, body weight (g), and total body fat (%) at all-time points up to 20 weeks post-injury (PI), while only severe SCI reduced the total body lean (%). Severe SCI increased liver echogenicity starting from 12 weeks PI, with an increase in liver fibrosis in both moderate and severe SCI. Severe SCI mice showed a significant reduction in left ventricular internal diameters and LV volume at 20 weeks PI, associated with increased LV ejection fraction as well as cardiac fibrosis. These cardiometabolic dysfunctions were accompanied by changes in the inflammation profile, varying with the severity of the injury, but not in the lipid profile nor cardiac or hepatic tyrosine hydroxylase innervation changes, suggesting that systemic inflammation may be involved in these SCI-induced health complications.

Effects of Arm-Crank Exercise on Fitness and Health in Adults With Chronic Spinal Cord Injury: A Systematic Review

Individuals with spinal cord injury (SCI) may benefit less from exercise training due to consequences of their injury, leading to lower cardiorespiratory fitness and higher risks of developing cardiovascular diseases. Arm-crank exercise (ACE) is the most common form of volitional aerobic exercise used by people with SCI outside a hospital. However, evidence regarding the specific effects of ACE alone on fitness and health in adults with SCI is currently lacking. Hence, this review aimed to determine the effects of ACE on cardiorespiratory fitness, body composition, cardiovascular disease (CVD) risk factors, motor function, health-related quality of life (QoL), and adverse events in adults with chronic SCI. Inclusion criteria were: inactive adults (≥18 years) with chronic SCI (>12 months post injury); used ACE alone as an intervention; measured at least one of the following outcomes; cardiorespiratory fitness, body composition, cardiovascular disease risk factors, motor function, health-related QoL, and adverse events. Evidence was synthesized and appraised using GRADE. Eighteen studies with a combined total of 235 participants having an injury between C4 to L3 were included. There was a moderate certainty of the body of evidence on ACE improving cardiorespiratory fitness. Exercise prescriptions from the included studies were 30-40 min of light to vigorous-intensity exercise, 3-5 times per week for 2-16 weeks. GRADE confidence ratings were very low for ACE improving body composition, CVD risks factors, motor function, or health-related QoL. No evidence suggests ACE increases the risk of developing shoulder pain or other injuries. Overall, this review recommends adults with chronic SCI should engage in regular ACE to improve cardiorespiratory fitness. More high-quality, larger-scale studies are needed to increase the level of evidence of ACE in improving cardiorespiratory fitness and to determine the effects of ACE on other outcomes. Systematic Review Registration: [https://www.crd.york.ac.uk/prospero/display_reco rd.php?ID=CRD42021221952], identifier [CRD42021221952].

Spinal cord injury impairs cardiac function due to impaired bulbospinal sympathetic control

Spinal cord injury chronically alters cardiac structure and function and is associated with increased odds for cardiovascular disease. Here, we investigate the cardiac consequences of spinal cord injury on the acute-to-chronic continuum, and the contribution of altered bulbospinal sympathetic control to the decline in cardiac function following spinal cord injury. By combining experimental rat models of spinal cord injury with prospective clinical studies, we demonstrate that spinal cord injury causes a rapid and sustained reduction in left ventricular contractile function that precedes structural changes. In rodents, we experimentally demonstrate that this decline in left ventricular contractile function following spinal cord injury is underpinned by interrupted bulbospinal sympathetic control. In humans, we find that activation of the sympathetic circuitry below the level of spinal cord injury causes an immediate increase in systolic function. Our findings highlight the importance for early interventions to mitigate the cardiac functional decline following spinal cord injury.

By combining experimental models with prospective clinical studies, the authors show that spinal cord injury causes a rapid reduction in cardiac function that precedes structural changes, and that the loss of descending sympathetic control is the major cause of reduced cardiac function following spinal cord injury.

The role of electrical stimulation for rehabilitation and regeneration after spinal cord injury

Electrical stimulation is used to elicit muscle contraction and can be utilized for neurorehabilitation following spinal cord injury when paired with voluntary motor training. This technology is now an important therapeutic intervention that results in improvement in motor function in patients with spinal cord injuries. The purpose of this review is to summarize the various forms of electrical stimulation technology that exist and their applications. Furthermore, this paper addresses the potential future of the technology.

Impact of tetraplegia vs. paraplegia on venoarteriolar, myogenic and maximal cutaneous vasodilation responses of the microvasculature: Implications for cardiovascular disease

Objective: Cardiovascular disease (CVD) is a leading cause of mortality in persons with SCI. While macrovascular remodeling and function after SCI is well documented, changes in the microvascular structure and function are comparably understudied, but importantly predict CVD risk. Specifically, the integrity of venoarteriolar (VAR), myogenic (MYO) and maximal vasodilation responses are largely unknown after SCI, especially in persons with tetraplegia (TP) at highest risk of CVD. This is the first to examine the differences in VAR (cuff inflation), MYO (limb dependency) and maximal vasodilation responses of the microvasculature between able bodied (AB) versus those with TP and paraplegia (PP).Design: Observational.Setting: Laboratory.Participants: Eight AB, 6 TP, and 8 PP persons.Interventions: One forearm and calf were treated topically with lidocaine 2.5%/prilocaine 2.5% while contralateral limb served as a control. Laser doppler flowmeters were applied over treated and control sites during limb dependency, cuff inflation and local skin heating (Tloc) up to 42°C.Outcome measures: Skin vascular resistance (SkVR) change with cuff inflation and limb dependency and maximal cutaneous vascular conductance (CVC) during local heating.Results: Change in SkVR was not significantly different between groups or extremity (upper vs. lower) during cuff inflation or limb dependency. However, CVC at Tloc 42°C was significantly different in the lower extremity (LE) of TP and PP (P = 0.007, 0.35) compared to AB.Conclusion: Increases in SkVR during cuff inflation (VAR) and limb dependency (VAR and MYO) are unaltered after SCI, however maximal vasodilation in the LE post-SCI is higher than AB persons.

Experimental high thoracic spinal cord injury impairs the cardiac and cerebrovascular response to orthostatic challenge in rats

Spinal cord injury (SCI) impairs the cardiovascular responses to postural challenge, leading to the development of orthostatic hypotension (OH). Here, we apply lower body negative pressure (LBNP) to rodents with high-level SCI to demonstrate the usefulness of LBNP as a model for experimental OH studies, and to explore the effect of simulated OH on cardiovascular and cerebrovascular function following SCI. Male Wistar rats (n = 34) were subjected to a sham or T3-SCI surgery and survived into the chronic period postinjury (i.e., 8 wk). Cardiac function was tracked via ultrasound pre- to post-SCI to demonstrate the clinical utility of our model. At study termination, we conducted left-ventricular (LV) catheterization and insonated the middle cerebral artery to investigate the hemodynamic, cardiac, and cerebrovascular response to a mild dose of LBNP that is sufficient to mimic clinically defined OH in rats with T3-SCI but not sham animals. In response to mimicked OH, there was a greater decline in stroke volume, cardiac output, maximal LV pressure, and blood pressure in SCI compared with sham (P < 0.034), whereas heart rate was increased in sham but decreased in SCI (P < 0.029). SCI animals also had an exaggerated reduction in peak, minimum and mean middle cerebral artery flow, for a given change in blood pressure, in response to LBNP (P < 0.033), implying impaired dynamic cerebral autoregulation. Using a preclinical SCI model of OH, we demonstrate that complete high thoracic SCI impairs the cardiac response to OH and disrupts dynamic cerebral autoregulation.NEW & NOTEWORTHY This is the first use of LBNP to interrogate the cardiac and cerebrovascular responses to simulated OH in a preclinical study of SCI. Here, we demonstrate the utility of our simulated OH model and use it to demonstrate that SCI impairs the cardiac response to simulated OH and disrupts dynamic cerebrovascular autoregulation.

Exercise Improves Cardiorespiratory Fitness, but Not Arterial Health, after Spinal Cord Injury: The CHOICES Trial

Arterial stiffness, as measured by carotid-femoral pulse wave velocity (cfPWV), is elevated after spinal cord injury (SCI). In the uninjured population, exercise training has been shown to reduce arterial stiffness. In a randomized, multi-center clinical trial, we evaluated the impact of two exercise interventions on cardiovascular disease risk factors in persons with chronic SCI. A total of 46 adults with motor-complete SCI with neurological levels of injury between the fourth cervical and sixth thoracic spinal cord segments (C4-T6) were randomly assigned to either body-weight-supported treadmill training (BWSTT) or arm-cycle ergometer training (ACET). Participants trained 3 days per week for 24 weeks. Exercise session duration progressed gradually to reach 30 and 60 min for ACET and BWSTT, respectively. The primary outcome was arterial stiffness, assessed by cfPWV, and was measured at baseline, 12 weeks of training, and at 24 weeks. Secondary outcomes included cardiorespiratory fitness (CRF) and cardiometabolic health measures and were measured before and after completion of training. Fourteen participants per intervention arm completed the exercise intervention. Our results show no effect of either exercise intervention on arterial stiffness (p = 0.07) and cardiometabolic health measures (p > 0.36). However, peak oxygen uptake increased with ACET compared with BWSTT (p = 0.04). The findings of this trial demonstrate that although 24 weeks of upper-body exercise improved CRF in persons with motor-complete SCI ≥T6, neither intervention resulted in improvements in arterial stiffness or cardiometabolic health measures. ClinicalTrials.gov identifier: NCT01718977.

Reductions in Cardiac Structure and Function 24 Months After Spinal Cord Injury: A Cross-Sectional Study

OBJECTIVE

To determine the alterations in cardiac structure and function that occur in the months after spinal cord injury (SCI).

STUDY DESIGN

Cross-sectional SETTING: Rehabilitation Hospital PARTICIPANTS: Volunteers (N=29; 4 women, 25 men) between 3 and 24 months after SCI.

MAIN OUTCOME MEASURES

Transthoracic echocardiography was performed on each volunteer. The relationships between time since injury and neurologic and sensory levels of injury to cardiac structure and function were assessed via multiple linear regression.

RESULTS

Time since injury was most strongly associated with reductions in left ventricular end diastolic volume (r2=0.156; P=.034), end systolic volume (r2=0.141; P=.045), and mass (r2=0.138; P=.047). These structural changes were paralleled by reduced stroke volume (r2=0.143; P=.043) and cardiac output (r2=0.317; P=<.001). The reductions in left ventricular structure and systolic function were not differentially affected by neurologic or sensory levels of injury (P=.084-.921).

CONCLUSIONS

These results suggest progressive reductions in left ventricular structure and systolic function between 3 and 24 months after SCI that occur independent of neurologic and sensory levels of injury.

Characteristics and Survival of Patients with Acute Traumatic Spinal Cord Injury Above T6 with Prolonged Intensive Care Unit Stays

OBJECTIVE

To characterize patients with acute traumatic spinal cord injury (ATSCI) above T6 who were admitted to the intensive care unit (ICU) for ≥30 days and their 1-year mortality compared with patients admitted for <30 days.

METHODS

A retrospective observational study was performed on 211 patients with an acute traumatic spinal cord injury above T6 who were admitted to an ICU between 1998 and 2017. Multivariate logistic regression analysis was performed to determine the relationship between an ICU stay ≥30 days and mortality after ICU discharge.

RESULTS

Of patients, 29.4% were admitted to the ICU for ≥30 days, accounting for 53.4% of total days of ICU stays generated by all patients. An ICU stay ≥30 days was not identified as an independent risk factor for mortality (1-year survival: 88.5% vs. 88.1%; adjusted hazard ratio [HR] 0.80, P = 0.699). Variables identified as predictors of 1-year post-ICU discharge mortality were severity at admission according to the Acute Physiology and Chronic Health Evaluation II score (HR 1.18) and the American Spinal Injury Association Impairment Scale motor score (HR 0.97). Among patients who required invasive mechanical ventilation, a longer duration of the respiratory support was associated with increased mortality (HR 1.01).

CONCLUSIONS

Three out of 10 patients with acute traumatic spinal cord injury above T6 require prolonged stays in the ICU. Variables found to be associated with 1-year post-ICU discharge mortality in these patients were American Spinal Injury Association Impairment Scale motor score, severity, and greater duration of invasive mechanical ventilation, but not an ICU stay ≥30 days.

Effects of a Tailored Physical Activity Intervention on Cardiovascular Structure and Function in Individuals With Spinal Cord Injury

Background

Spinal cord injury (SCI) leads to a loss of descending motor and sympathetic control below the level of injury (LOI), which ultimately results in chronically altered cardiovascular function and remodeling. While supervised, laboratory-based exercise training can generate cardiovascular adaptations in people with SCI, it is unknown whether behavioral community-based interventions effectively generate such adaptations for individuals with SCI.

Objective

Examine the effects of a tailored behavioral physical activity (PA) intervention on cardiac and vascular structure and function in individuals with SCI.

Methods

In this randomized controlled trial, 32 participants with SCI (18-65 years, SCI >1 year) were assigned to PA (8-week behavioral intervention) or control (CON) groups. At baseline and postintervention, measures of resting left ventricular (LV) structure and function, carotid intima-media thickness and pulse-wave velocity were assessed with ultrasound and tonometry.

Results

Twenty-eight participants completed the study (n = 14/group). Across the full study cohort there were no significant changes in indices of LV or vascular structure and function, despite notable improvements in peak power and oxygen uptake in the PA group. However, in a subanalysis for LOI, individuals in the PA group with LOIs below T6 had evidence of altered LV geometry (ie, increased LV internal diameter, reduced sphericity index and relative wall thickness; group × time P < 0.05 for all), which was not seen in individuals with higher LOIs at or above T6.

Conclusion

An 8-week behavioral PA intervention appears to promote adaptations in cardiac geometry more readily in individuals with lower level SCI than those with higher-level SCI.

Sex and gender gap in spinal cord injury research: Focus on cardiometabolic diseases. A mini review

Cardiometabolic disease (CMD) is among the leading causes of morbidity and mortality in people with a spinal cord injury (SCI). Despite well-acknowledged sex and gender differences in CMD in the general population, they remain insufficiently studied in persons with SCI. To describe the landscape of sex and gender in SCI research, we searched the literature for systematic reviews on cardiometabolic health in this population. Out of 15 systematic reviews identified, only 9 provided meaningful information on sex. Although one-quarter to one-fifth of the SCI population is female, women comprised only one-eighth to a quarter of study participants. A number of clinical studies purposively excluded women, to make the study population more homogenous. For those studies which included both sexes, in general, no sex-specific analyses were performed due to small sample sizes. All these reasons have contributed to the underrepresentation of females in the current body of evidence. Therefore, future studies should adopt a more sex- and gender-sensitive research framework to address cardiometabolic risk in SCI. Novel and advanced epidemiological methods should also be used, considering small sample sizes. Finally, collaborative research (through consortia and multi-center studies) should be encouraged to include more females. More inclusive research will ensure that everyone will benefit from scientific advancements, regardless of sex and gender.

Neurophysiological Changes in the First Year After Cell Transplantation in Sub-acute Complete Paraplegia

Neurophysiological testing can provide quantitative information about motor, sensory, and autonomic system connectivity following spinal cord injury (SCI). The clinical examination may be insufficiently sensitive and specific to reveal evolving changes in neural circuits after severe injury. Neurophysiologic data may provide otherwise imperceptible circuit information that has rarely been acquired in biologics clinical trials in SCI. We reported a Phase 1 study of autologous purified Schwann cell suspension transplantation into the injury epicenter of participants with complete subacute thoracic SCI, observing no clinical improvements. Here, we report longitudinal electrophysiological assessments conducted during the trial. Six participants underwent neurophysiology screening pre-transplantation with three post-transplantation neurophysiological assessments, focused on the thoracoabdominal region and lower limbs, including MEPs, SSEPs, voluntarily triggered EMG, and changes in GSR. We found several notable signals not detectable by clinical exam. In all six participants, thoracoabdominal motor connectivity was detected below the clinically assigned neurological level defined by sensory preservation. Additionally, small voluntary activations of leg and foot muscles or positive lower extremity MEPs were detected in all participants. Voluntary EMG was most sensitive to detect leg motor function. The recorded MEP amplitudes and latencies indicated a more caudal thoracic level above which amplitude recovery over time was observed. In contrast, further below, amplitudes showed less improvement, and latencies were increased. Intercostal spasms observed with EMG may also indicate this thoracic “motor level.” Galvanic skin testing revealed autonomic dysfunction in the hands above the injury levels. As an open-label study, we can establish no clear link between these observations and cell transplantation. This neurophysiological characterization may be of value to detect therapeutic effects in future controlled studies.

The neurological level of spinal cord injury and cardiovascular risk factors: a systematic review and meta-analysis

STUDY DESIGN

Systematic review and meta-analysis.

OBJECTIVE

To determine the difference in cardiovascular risk factors (blood pressure, lipid profile, and markers of glucose metabolism and inflammation) according to the neurological level of spinal cord injury (SCI).

METHODS

We searched 5 electronic databases from inception until July 4, 2020. Data were extracted by two independent reviewers using a pre-defined data collection form. The pooled effect estimate was computed using random-effects models, and heterogeneity was calculated using I² statistic and chi-squared test (CRD42020166162).

RESULTS

We screened 4863 abstracts, of which 47 studies with 3878 participants (3280 males, 526 females, 72 sex unknown) were included in the meta-analysis. Compared to paraplegia, individuals with tetraplegia had lower systolic and diastolic blood pressure (unadjusted weighted mean difference, -14.5 mmHg, 95% CI -19.2, -9.9; -7.0 mmHg 95% CI -9.2, -4.8, respectively), lower triglycerides (-10.9 mg/dL, 95% CI -19.7, -2.1), total cholesterol (-9.9 mg/dL, 95% CI -14.5, -5.4), high-density lipoprotein (-1.7 mg/dL, 95% CI -3.3, -0.2) and low-density lipoprotein (-5.8 mg/dL, 95% CI -9.0, -2.5). Comparing individuals with high- vs. low-thoracic SCI, persons with higher injury had lower systolic and diastolic blood pressure (-10.3 mmHg, 95% CI -13.4, -7.1; -5.3 mmHg 95% CI -7.5, -3.2, respectively), while no differences were found for low-density lipoprotein, serum glucose, insulin, and inflammation markers. High heterogeneity was partially explained by age, prevalent cardiovascular diseases and medication use, body mass index, sample size, and quality of studies.

CONCLUSION

In SCI individuals, the level of injury may be an additional non-modifiable cardiovascular risk factor. Future well-designed longitudinal studies with sufficient follow-up and providing sex-stratified analyses should confirm our findings and explore the role of SCI level in cardiovascular health and overall prognosis and survival.

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

Unstable blood pressure after spinal cord injury (SCI) is not routinely examined but rather predicted by level and completeness of injury (i.e., American Spinal Injury Association Impairment Scale AIS classification). Our aim was to investigate hemodynamic response to a sit-up test in a large cohort of individuals with chronic SCI to better understand cardiovascular function in this population. Continuous blood pressure and ECG were recorded from individuals with SCI (n = 159) and non-injured individuals (n = 48). We found orthostatic hypotension occurred within each level and AIS classification (n = 36). Moreover, 45 individuals with chronic SCI experienced a drop in blood pressure that did not meet the criteria for orthostatic hypotension, but was accompanied by dramatic increases in heart rate, reflecting orthostatic intolerance. A cluster analysis of hemodynamic response to a seated position identified eight distinct patterns of interaction between blood pressure and heart rate during orthostatic stress indicating varied autonomic responses. Algorithmic cluster analysis of heart rate and blood pressure is more sensitive to diagnosing orthostatic cardiovascular dysregulation. This indicates blood pressure instability cannot be predicted by level and completeness of SCI, and the consensus statement definition of orthostatic hypotension is insufficient to characterize the variability of blood pressure and heart rate responses during orthostatic stress. Both blood pressure and heart rate responses are needed to characterize autonomic function after SCI.

Traditional Cardiovascular Risk Factors Strongly Underestimate the 5-Year Occurrence of Cardiovascular Morbidity and Mortality in Spinal Cord Injured Individuals

OBJECTIVES

To explore whether traditional models of cardiovascular disease (CVD) risk prediction correctly predict CVD events across a median 5.7-year follow-up period in individuals with spinal cord injury (SCI) and whether adding SCI-related characteristics (ie, lesion level) to the prediction model can improve the prognostic value.

DESIGN

Retrospective analysis of patient records.

SETTING

Observation at the start of active rehabilitation of participants in a multicenter cohort study, "Restoration of (Wheelchair) Mobility in SCI Rehabilitation," in the Netherlands.

PARTICIPANTS

Patients with SCI (N=200) The patients were 74% men, aged 40±14 years, and with an American Spinal Injury Association (ASIA) impairment score of A through D. Forty percent had tetraplegia, and 69% were motor complete.

INTERVENTIONS

Risk profiling/not applicable.

MAIN OUTCOME MEASURES

Survival status and cardiovascular morbidity and mortality qwere obtained from medical records. Five-year Framingham Risk Scores (FRS) and the FRS ability to predict events assessed using receiver operating characteristic (ROC) curves with corresponding areas under the curve (AUC) and 95% confidence intervals (CI). Kaplan-Meier curves and the log-rank test were used to assess the difference in clinical outcome between participants with an FRS score lower or higher than the median FRS score for the cohort. SCI-related factors associated with CVD events, ASIA impairment, motor completeness, level of injury, and sports participation before injury were explored using univariate and multivariate Cox proportional hazard regression.

RESULTS

The median 5-year FRS was 1.36%. Across a median follow-up period of 5.7 years, 39 developed a CVD event, including 10 fatalities. Although the FRS markedly underestimated the true occurrence of CVD events, the Kaplan-Meier curves and the log-rank test showed that the risk ratio for individuals with an FRS score less than the median FRS (eg, low risk) versus a score greater than the median FRS (high risk) was 3.2 (95% CI, 1.6-6.5; P=.001). Moreover, ROC with corresponding AUCs suggests acceptable accuracy of the FRS to identify individuals with increased risk for future CVD events (ROC AUC of 0.71; 95% CI, 0.62-0.82). Adding ASIA impairment (0.74; 95% CI, 0.66-0.82), motor impairment (0.74; 95% CI, 0.66-0.83), level of injury (0.72; 95% CI, 0.63-0.81), or active engagement in sport before injury (0.72; 95% CI, 0.63-0.88) to the FRS did not improve the level of discrimination.

CONCLUSIONS

Our 5.7-year retrospective study reveals that cardiovascular risk factors and risk models markedly underestimate the true risk for CVD events in individuals with SCI. Nonetheless, these markers successfully distinguish between SCI individuals at high versus low risk for future CVD events. Our data may have future clinical implications, both related to (cutoff values of) CVD risk factors, but also for (earlier) prescription of (non)pharmacologic strategies against CVD in SCI individuals.

Experimental study on the effectiveness of the PCM cooling vest in persons with paraplegia of varying levels

Persons with paraplegia (PA) from thoracic spinal cord injury (T1-T12) are prone to thermal stress during exercise due to impaired thermoregulation. This study evaluates the effectiveness of phase change material (PCM) cooling vests on persons with PA of different levels of injury during exercise in hot exposure. Sixteen participants were recruited and divided to three groups based on injury level; high-thoracic T1-T3, mid-thoracic T4-T8, and low thoracic T9-T12 to perform a 30-min arm-crank exercise at a 30 °C room condition. Two types of PCM vests at melting temperature of 20 °C were tested: i) V1 with PCM covering the trunk of 3.4 kg overall vest mass and ii) V2 with PCM covering chest and upper back of 2.17 kg overall vest mass. High thoracic and low-thoracic groups performed NV and V1 tests; whereas, mid-thoracic group performed NV, V1, and V2 tests. Heart rate, core, and skin temperatures were monitored during 15-min preconditioning, 30-min exercise, and 15-min recovery. In addition, thermal comfort, sensation, skin wettedness, and perceived exertion were recorded during exercise only. The main findings were that the effectiveness of the cooling vest was dependent on injury level and portion of sensate skin of trunk covered by the PCM packets. Rise in core temperature (ΔT_cr) was reduced significantly for the low-thoracic group during exercise and recovery (ΔT_cr=0.41°C, 0.26°C for NV and V1; respectively, p<0.05). For the mid-thoracic group, both V1 (p = 0.001) and V2 (p = 0.008) were effective in reducing ΔT_cr compared to the NV test at the end of the recovery period (0.74°C,0.42°C,0.56°C, for NV, V1 and V2; respectively). For the high-thoracic group, V1 was not effective in reducing core temperature (p>0.05). For the mid-thoracic group, V2 at 36% lower mass significantly improved thermal comfort (p = 0.0004) compared to the NV test and was as effective compared to V1 in reducing core temperature.

Classification of obesity, cardiometabolic risk, and metabolic syndrome in adults with spinal cord injury

Objective: To describe and compare (1) classification of obesity using clinical proxies of body composition that are easily accessible in the outpatient clinic setting, (2) cardiometabolic risk using existing screening tools and staging systems, and (3) the presence of metabolic syndrome (MetS) using four commonly-used definitions in adults with spinal cord injury (SCI). Design: Retrospective chart review Setting: Outpatient Veterans Affairs (VA) SCI Annual Evaluation Clinic Participants: Patients who attended an annual evaluation appointment with demographic, anthropometric, and biochemical data documented in their medical records as part of routine medical care. Outcome measures: Obesity classification (body mass index, waist circumference, ideal body weight percentage), cardiometabolic risk scores (Framingham Risk Score, Cardiometabolic Disease Staging System, Edmonton Obesity Staging System), and MetS classification (using four commonly-used definitions) were described and compared. Results: Of the 155 veterans included in this analysis, 93% were considered "at risk" by at least one of the measurements studied. However, there was considerable variation between the different screening tools. The κ-agreement between various definitions of MetS ranged from fair to moderate. Conclusion: Screening tools that were developed for the non-SCI population produced variable assessments of risk when applied to veterans with SCI. Due to the fair to moderate inter-rater agreement between MetS definitions, it is unknown which definition is superior to identify MetS in the SCI population. An SCI-specific screening tool is needed to accurately classify obesity, cardiometabolic risk, and MetS in order to provide timely education and intervention.

Use of actigraphy to measure real-world physical activities in manual wheelchair users

Introduction

The benefits of physical activity for manual wheelchair users are well-known. The purpose of this study was to validate actigraphy to objectively measure physical activity intensity among manual wheelchair users.

Method

An experimental design was used. Adult manual wheelchair users wore a GT3X actigraph on their non-dominant arm while completing eight physical activities of low (reading), moderate (propelling -- flat) and high (propelling -- steep ramp) intensity. Heart rate and rating of perceived exertion were collected at the end of each physical activity. Distribution of data were examined and used to determine the type of repeated measures (parametric vs. non-parametric). A categorical principal component analysis was performed to determine the amount of variability explained by actigraphy, heart rate and rating of perceived exertion. Activity count cut-points were estimated using bootstrapping methods.

Results

Twenty-eight manual wheelchair users completed the study. Actigraphy, heart rate and rating of perceived exertion co-varied as physical activity intensity changed. Activity counts for low-intensity and medium-intensity physical activities were estimated to be 0 to 45 and 45 to 100 activity counts per second, respectively. Activity counts' ranges for high-intensity physical activities were not clear.

Conclusion

Combining actigraphy and rating of perceived exertion could be an easy and reliable method to measure the intensity of real-world activities. Further research is needed confirm cut-points for physical activity intensity.

A porcine model for studying the cardiovascular consequences of high-thoracic spinal cord injury

KEY POINTS

We have developed a novel porcine model of high-thoracic midline contusion spinal cord injury (SCI) at the T2 spinal level. We describe this model and the ensuing cardiovascular and neurohormonal responses, and demonstrate the model is efficacious for studying clinically relevant cardiovascular dysfunction post-SCI. We demonstrate that the high-thoracic SCI model, but not a low-thoracic SCI model, induces persistent hypotension along with a gradual reduction in plasma noradrenaline and increases in plasma aldosterone and angiotensin II. We additionally conducted a proof-of-concept long-term (12 weeks) survival study in animals with T2 contusion SCI demonstrating the potential utility of this model for not only acute experimentation but also long-term drug studies prior to translation to the clinic.

ABSTRACT

Cardiovascular disease is a leading cause of morbidity and mortality in the spinal cord injury (SCI) population, especially in those with high-thoracic or cervical SCI. With this in mind, we aimed to develop a large animal (porcine) model of high-thoracic (T2 level) contusion SCI and compare the haemodynamic and neurohormonal responses of this injury against a low-thoracic (T10 level) model. Ten Yorkshire pigs were randomly subjected to 20 cm weight drop contusion SCI at either the T2 or the T10 spinal level. Systolic blood pressure (SBP), mean arterial pressure (MAP) and heart rate (HR) were continuously monitored until 4 h post-SCI. Plasma noradrenaline (NA), aldosterone and angiotensin II (ANGII) were measured pre-SCI and at 30, 60, 120 and 240 min post-SCI. Additionally, two Yucatan pigs were subjected to T2-SCI and survived up to 12 weeks post-injury to demonstrate the efficacy of this model for long-term survival studies. Immediately after T2-SCI, SBP, MAP and HR increased (P < 0.0001). Between decompression (5 min post-SCI) and 30 min post-decompression in T2-SCI, SBP and MAP were lower than pre-SCI (P < 0.038). At 3 and 4 h after T2-SCI, SBP remained lower than pre-SCI (P = 0.048). After T10-SCI, haemodynamic indices remained largely unaffected. Plasma NA was lower in T2- vs. T10-SCI post-SCI, whilst aldosterone and ANGII were higher. Both chronically injured pigs demonstrated a vast reduction in SBP at 12 weeks post-SCI. Our model of T2-SCI causes a rapid and sustained alteration in neurohormonal control and cardiovascular function, which does not occur in the T10 model.

Bioenergetics and Biomechanics of Handcycling at Submaximal Speeds in Athletes with a Spinal Cord Injury

BACKGROUND

A study aimed at comparing bioenergetics and biomechanical parameters between athletes with tetraplegia and paraplegia riding race handbikes at submaximal speeds in ecological conditions.

METHODS

Five athletes with tetraplegia (C6-T1, 43 ± 6 yrs, 63 ± 14 kg) and 12 athletes with paraplegia (T4-S5, 44 ± 7 yrs, 72 ± 12 kg) rode their handbikes at submaximal speeds under metabolic measurements. A deceleration method (coasting down) was applied to calculate the rolling resistance and frontal picture of each participant was taken to calculate air resistance. The net overall Mechanical Efficiency (Eff) was calculated by dividing external mechanical work to the corresponding Metabolic Power.

RESULTS

Athletes with tetraplegia reached a lower aerobic speed (4.7 ± 0.6 m s^-1 vs. 7.1 ± 0.9 m s^-1, P = 0.001) and Mechanical Power (54 ± 15 W vs. 111 ± 25 W, P = 0.001) compared with athletes with paraplegia. The metabolic cost was around 1 J kg^-1 m^-1 for both groups. The Eff values (17 ± 2% vs. 19 ± 3%, P = 0.262) suggested that the handbike is an efficient assisted locomotion device.

CONCLUSION

Handbikers with tetraplegia showed lower aerobic performances but a similar metabolic cost compared with handbikers with paraplegia at submaximal speeds in ecological conditions.

Blood Pressure Instability in Persons With SCI: Evidence From a 30-Day Home Monitoring Observation

BACKGROUND

To determine the degree of blood pressure instability over a 30-day home observation in participants with spinal cord injury grouped by level of injury pertaining to cardiovascular autonomic regulation.

METHODS

This is an observational study completed at the Kessler Foundation and James J. Peters Veterans Medical Center. Seventy-two participants with tetraplegia (C1-T1), 13 with high thoracic (T2-T4), and 28 with low thoracic (T5-T12) injury participated in this study. Participants were asked to record their blood pressure using an ambulatory blood pressure monitor three times a day for 30 days.

RESULTS

The number of blood pressure fluctuations was significantly increased in the tetraplegia group compared with the paraplegia groups. Age and duration of injury contributed to an increase in the observation of 30-day blood pressure instability; however, completeness of injury did not.

CONCLUSION

The data indicate significant blood pressure instability that may not be exclusive to persons with tetraplegia; in fact, individuals with low thoracic injuries demonstrated severe blood pressure fluctuations. The use of a monitor at home for an extended period may help document dangerous and extreme fluctuations in blood pressure and should be considered an important adjunctive clinical practice for tracking of the secondary consequences in the spinal cord injury population.

Poor specificity of National Early Warning Score (NEWS) in spinal cord injuries (SCI) population: a retrospective cohort study

STUDY DESIGN

Retrospective chart audit.

OBJECTIVES

The National Early Warning Score (NEWS) is based on seven physiological parameters which can be altered in some individuals with spinal cord injuries (SCI). The aim was to start the development of adapted NEWS suitable for SCI population. The objective was to determine the SBP NEWS specificity based on neurological level of injury (NLI) and completeness of injury.

SETTING

Tertiary centre in the UK.

METHODS

Adult patients admitted for the first time to the National Spinal Injuries Centre between 1 January 2015 and 31 December 2016 were included if they were >6 months post injury. Data were extracted retrospectively including the last ten consecutive BP and heart rate readings before discharge. Data were analysed based on different AIS grades, completeness of injury and NLI.

RESULTS

One hundred and ninety one patients were admitted in 2015 and 2016 and 142 patients were included in the primary analysis. The mean SBP ranged between 92 and 151 mmHg. Patients with the NLI of T6 and above (≥T6) motor complete lesions had a significantly lower SBP than motor incomplete lesions. The specificity of the SBP NEWS was 35.3% in ≥T6 motor complete individuals versus 80.3% in ≥T6 motor incomplete individuals.

CONCLUSION

The baseline BP is significantly lower in the ≥T6 motor complete SCI individuals (>6 months post injury) resulting in a very low specificity of 35.3% to SBP NEWS, which could lead to mismatch between clinical deterioration and NEWS resulting in lack of timely clinical response.

Would personal cooling vest be effective for use during exercise by people with thoracic spinal cord injury?

People with thoracic spinal cord injury (SCI), named people with paraplegia (PA), are vulnerable to thermal heat stress during exercise due to disruption in their thermal physiology. Using personal cooling vests with phase change material (PCM) or ice presents a possible solution for PA to suppress the increase in core temperature and body heat storage. With the limited published experimental studies about effective cooling vest for PA, this work aims to develop an altered PA bioheat model combined with cooling vest model to study cooling vest performance during exercise. The integrated PA bioheat and vest models predict core and skin temperatures, latent and sensible heat losses and change in body heat storage for PA with and without a cooling vest. The models were validated with published experimental data on PA without the cooling vest and on PA with two cooling vests; one using PCM at melting temperature of 15 °C and the other using ice packets during exercise. It was observed that sensible heat losses at the four torso segments (abdomen, lower back, chest and upper back) increased with the vest case compared to the no-vest case; while, latent heat losses decreased compared to the no-vest case. However, insignificant change was seen in core temperatures and body heat storage as was also reported experimentally. The performance of each of the cooling vest during exercise on PA was dependent on skin coverage area and melting temperatures.

Temporal analysis of cardiovascular control and function following incomplete T3 and T10 spinal cord injury in rodents

Spinal cord injury (SCI) is a devastating condition that results in whole‐body dysfunction, notably cardiovascular (CV) disruption and disease. Injury‐induced destruction of autonomic pathways in conjunction with a progressive decline in physical fitness contribute to the poor CV status of SCI individuals. Despite the wide use of exercise training as a therapeutic option to reduce CV dysfunction, little is known about the acute hemodynamic responses to the exercise itself. We investigated CV responses to an exercise challenge (swimming) following both high and low thoracic contusion to determine if the CV system is able to respond appropriately to the challenge of swimming. Blood pressure (BP) telemetry and echocardiography were used to track the progression of dysfunction in rodents with T3 and T10 SCI (n = 8 each) for 10 weeks postcontusion. At 1 week postinjury, all animals displayed a drastic decline in heart rate (HR) during the exercise challenge, likely a consequence of neurogenic shock. Furthermore, over time, all groups developed a progressive inability to maintain BP within a narrow range during the exercise challenge despite displaying normal hemodynamic parameters at rest. Echocardiography of T10 animals revealed no persistent signs of cardiac dysfunction; T3 animals exhibited a transient decline in systolic function that returned to preinjury levels by 10 weeks postinjury. Novel evidence provided here illustrates that incomplete injuries produce hemodynamic instability that only becomes apparent during an exercise challenge. Further, this dysfunction lasts into the chronic phase of disease progression despite significant recovery of hindlimb locomotion and cardiac function.

The effect of level of injury and physical activity on heart rate variability following spinal cord injury

OBJECTIVE/BACKGROUND

To assess frequency domain heart rate variability (HRV) parameters at rest and in response to postural autonomic provocations in individuals with spinal cord injury (SCI) and investigate the autonomic influences on the heart of different physical activities.

DESIGN

Cross-sectional study.

METHODS

Ten subjects with complete cervical SCI and fourteen subjects with complete low thoracic SCI were prospectively recruited from the community and further divided in sedentary and physically active groups, the latter defined as regular weekly 4 hour physical activity for the preceding 3 months. Sixteen healthy individuals matched for sex and age were recruited to participate in the control group. The Low Frequency (LF), High Frequency (HF) powers and the LF/HF ratio of HRV were measured from continuous electrocardiogram (ECG) recordings at rest and after sitting using a fast Fourier transformation.

OUTCOME MEASURES

The LF,HF, and the LF/HF ratio at rest and after sitting.

RESULTS

A significant decrease in all HRV parameters in patients with SCI was found compared to controls. The change in HF, LF and LF/HF following sitting maneuver was significantly greater in controls as compared with the SCI group and greater in subjects with paraplegia as compared to subjects with tetraplegia. Better HRV values and enhanced vagal activity appears to be related to the type of physical activity in active subjects with paraplegia.

CONCLUSION

In this cohort of subjects spectral parameters of HRV were associated with the level of the injury. Passive standing was associated with higher HRV values in subjects with paraplegia.

Haemodynamic changes during prone positioning in anaesthetised chronic cervical myelopathy patients

Background and Aims:

Anaesthetised patients, when positioned prone, experience hypotension and reduction in cardiac output. Associated autonomic dysfunction in cervical myelopathy patients predisposes them to haemodynamic changes. The combined effect of prone positioning and autonomic dysfunction in anaesthetised patients remains unknown.

Methods:

Thirty adult chronic cervical myelopathy patients, aged 18-65 years with Nurick grade ≥2 were recruited in this prospective observational study. Heart rate, mean blood pressure, cardiac output, stroke volume, total peripheral resistance and stroke volume variation were measured using NICOM^® monitor. Data were collected in supine before anaesthetic induction (baseline), 2 minutes after induction, 2 minutes after intubation, before and after prone positioning and every 5 minutes thereafter until skin incision. Repeated measures analysis of variance (ANOVA) was used to analyse the haemodynamic parameters across the time points. Bivariate Spearman's correlation was used to find factors associated with blood pressure changes. A P value <0.05 was kept significant.

Results:

Cardiac output during the entire study period remained stable (P = 0.186). Sixty percent of the patients experienced hypotension. At 15 and 20 minutes after prone positioning, mean blood pressure decreased (P = 0.001), stroke volume increased (P = 0.001), and heart rate and total peripheral resistance decreased (P < 0.001, P = 0.001, respectively). These changes were significant when compared to pre-prone position values. Number of levels of spinal cord compression positively correlated with the incidence of hypotension.

Conclusion:

Cervical myelopathy patients experienced hypotension with preserved cardiac output in prone position due to a reduction in total peripheral resistance. Hypotension correlated with the number of levels of spinal cord compression.

Cardiac consequences of spinal cord injury: systematic review and meta-analysis

OBJECTIVE

Conduct a meta-analysis to determine the impact of traumatic spinal cord injury (SCI) on echocardiographic measurements of left ventricular (LV) structure and function.

METHODS

MEDLINE and Embase were used for primary searches of studies reporting LV echocardiographic data in individuals with SCI. Of 378 unique citations, 36 relevant full-text articles were retrieved, and data from 27 studies were extracted for meta-analyses. Literature searches, article screening and data extraction were completed by two independent reviewers and compared for agreement. Primary analyses compared echocardiographic indices between individuals with SCI and able-bodied individuals, using a random effects model.

RESULTS

Data are reported as pooled effect estimates (95% CI). Data from 22 articles (474 participants) were included in the primary meta-analysis. Compared with able-bodied individuals, individuals with SCI had reductions to LV stroke volume of 11.8 mL (95% CI -17.8 to -5.9, p<0.001), end-diastolic volume of 19.6 mL (95% CI -27.2 to -11.9, p<0.001) and LV mass_index of -7.7 g/m² (95% CI -11.6 to -3.8, p<0.001), but ejection fraction was not different between the groups (95% CI -2.6% to 0.6%, p=0.236). Individuals with SCI also had altered indices of diastolic function, specifically a lowered ratio of early-to-late filling velocities (p=0.039), and augmented ratio of early diastolic flow-to-tissue velocities (p=0.021).

CONCLUSIONS

Individuals with SCI have smaller LV volumes and mass, and altered systolic and diastolic function. While this meta-analysis demonstrates important alterations to echocardiographic measures of cardiac structure and function at rest, future work should consider the impacts of SCI on the heart's capacity or 'reserve' to respond to physiological challenges.

PROSPERO REGISTRATION NUMBER

CRD42017072333.

Autonomic Nervous System in Paralympic Athletes with Spinal Cord Injury

Individuals sustaining a spinal cord injury (SCI) frequently suffer from sensorimotor and autonomic impairment. Damage to the autonomic nervous system results in cardiovascular, respiratory, bladder, bowel, and sexual dysfunctions, as well as temperature dysregulation. These complications not only impede quality of life, but also affect athletic performance of individuals with SCI. This article summarizes existing evidence on how damage to the spinal cord affects the autonomic nervous system and impacts the performance in athletes with SCI. Also discussed are frequently used performance-enhancing strategies, with a special focus on their legal aspect and implication on the athletes' health.

Peak oxygen uptake in Paralympic sitting sports: A systematic literature review, meta- and pooled-data analysis

Background

Peak oxygen uptake (VO_2peak) in Paralympic sitting sports athletes represents their maximal ability to deliver energy aerobically in an upper-body mode, with values being influenced by sex, disability-related physiological limitations, sport-specific demands, training status and how they are tested.

Objectives

To identify VO_2peak values in Paralympic sitting sports, examine between-sports differences and within-sports variations in VO_2peak and determine the influence of sex, age, body-mass, disability and test-mode on VO_2peak.

Design

Systematic literature review and meta-analysis.

Data sources

PubMed, CINAHL, SPORTDiscus^TM and EMBASE were systematically searched in October 2016 using relevant medical subject headings, keywords and a Boolean.

Eligibility criteria

Studies that assessed VO_2peak values in sitting sports athletes with a disability in a laboratory setting were included.

Data synthesis

Data was extracted and pooled in the different sports disciplines, weighted by the Dersimonian and Laird random effects approach. Quality of the included studies was assessed with a modified version of the Downs and Black checklist by two independent reviewers. Meta-regression and pooled-data multiple regression analyses were performed to assess the influence of sex, age, body-mass, disability, test mode and study quality on VO_2peak.

Results

Of 6542 retrieved articles, 57 studies reporting VO_2peak values in 14 different sitting sports were included in this review. VO_2peak values from 771 athletes were used in the data analysis, of which 30% participated in wheelchair basketball, 27% in wheelchair racing, 15% in wheelchair rugby and the remaining 28% in the 11 other disciplines. Fifty-six percent of the athletes had a spinal cord injury and 87% were men. Sports-discipline-averaged VO_2peak values ranged from 2.9 L∙min^-1 and 45.6 mL∙kg^-1∙min^-1 in Nordic sit skiing to 1.4 L∙min^-1 and 17.3 mL∙kg^-1∙min^-1 in shooting and 1.3 L∙min^-1 and 18.9 mL∙kg^-1∙min^-1 in wheelchair rugby. Large within-sports variation was found in sports with few included studies and corresponding low sample sizes. The meta-regression and pooled-data multiple regression analyses showed that being a man, having an amputation, not being tetraplegic, testing in a wheelchair ergometer and treadmill mode, were found to be favorable for high absolute and body-mass normalized VO_2peak values. Furthermore, high body mass was favourable for high absolute VO_2peak values and low body mass for high body-mass normalized VO_2peak values.

Conclusion

The highest VO_2peak values were found in Nordic sit skiing, an endurance sport with continuously high physical efforts, and the lowest values in shooting, a sport with low levels of displacement, and in wheelchair rugby where mainly athletes with tetraplegia compete. However, VO_2peak values need to be interpreted carefully in sports-disciplines with few included studies and large within-sports variation. Future studies should include detailed information on training status, sex, age, test mode, as well as the type and extent of disability in order to more precisely evaluate the effect of these factors on VO_2peak.

Chronic, complete cervical6-7 cord transection: distinct autonomic and cardiac deficits

Spinal cord injury (SCI) resulting in tetraplegia is a devastating, life-changing insult causing paralysis and sensory impairment as well as distinct autonomic dysfunction that triggers compromised cardiovascular, bowel, bladder, and sexual activity. Life becomes a battle for independence as even routine bodily functions and the smallest activity of daily living become major challenges. Accordingly, there is a critical need for a chronic preclinical model of tetraplegia. This report addresses this critical need by comparing, for the first time, resting-, reflex-, and stress-induced cardiovascular, autonomic, and hormonal responses each week for 4 wk in 12 sham-operated intact rats and 12 rats with chronic, complete C_6-7 spinal cord transection. Loss of supraspinal control to all sympathetic preganglionic neurons projecting to the heart and vasculature resulted in a profound bradycardia and hypotension, reduced cardiac sympathetic and parasympathetic tonus, reduced reflex- and stress-induced sympathetic responses, and reduced sympathetic support of blood pressure as well as enhanced reliance on angiotensin to maintain arterial blood pressure. Histological examination of the nucleus ambiguus and stellate ganglia supports the profound and distinct autonomic and cardiac deficits and reliance on angiotensin to maintain cardiovascular stability following chronic, complete cervical_6-7 cord transection. NEW & NOTEWORTHY For the first time, resting-, reflex-, and stress-induced cardiovascular, autonomic, and hormonal responses were studied in rats with chronic, complete C_6-7 cord transection. Loss of supraspinal control of all sympathetic preganglionic neurons reduced cardiac sympathetic and parasympathetic tonus, reflex and stress-induced sympathetic responses, and sympathetic support of blood pressure as well as enhanced reliance on angiotensin to maintain arterial blood pressure. Histological examination supports the distinct deficits associated with cervical cord injury.

Spinal Cord Injury Causes Systolic Dysfunction and Cardiomyocyte Atrophy

Individuals with spinal cord injury (SCI) have been shown to exhibit systolic, and to a lesser extent, diastolic cardiac dysfunction. However, previous reports of cardiac dysfunction in this population are confounded by the changing loading conditions after SCI and as such, whether cardiac dysfunction per se is present is still unknown. Therefore, our aim was to establish if load-independent cardiac dysfunction is present after SCI, to understand the functional cardiac response to SCI, and to explore the changes within the cellular milieu of the myocardium. Here, we applied in vivo echocardiography and left-ventricular (LV) pressure-volume catheterization with dobutamine infusions to our Wistar rodent model of cardiac dysfunction 5 weeks following high (T2) thoracic contusion SCI, while also examining the morphological and transcriptional alterations of cardiomyocytes. We found that SCI significantly impairs systolic function independent of loading conditions (end-systolic elastance in control: 1.35 ± 0.15; SCI: 0.65 ± 0.19 mm Hg/μL). The reduction in contractile indices is accompanied by a reduction in width and length of cardiomyocytes as well as alterations in the LV extracellular matrix. Importantly, we demonstrate that the reduction in the rate (dP/dtmax) of LV pressure rise can be offset with beta-adrenergic stimulation, thereby experimentally implicating the loss of descending sympatho-excitatory control of the heart as a principle cause of LV dysfunction in SCI. Our data provide evidence that SCI induces systolic cardiac dysfunction independent of loading conditions and concomitant cardiomyocyte atrophy that may be underpinned by changes in the genes regulating the cardiac extracellular matrix.

Spinal cord injury-induced cardiomyocyte atrophy and impaired cardiac function are severity dependent

NEW FINDINGS

What is the central question of this study? How does the severity of spinal cord injury affect left ventricular mechanics, function and the underlying cardiomyocyte morphology? What is the main finding and its importance? Here, we show that severe, but not moderate, spinal cord injury causes cardiomyocyte atrophy, altered left ventricular mechanics and impaired cardiac function. The principal aim of the present study was to assess how the severity of spinal cord injury (SCI) affects left ventricular (LV) mechanics, function and underlying cardiomyocyte morphology. Here, we used different severities of T3 spinal cord contusions (MODERATE, 200 kdyn contusion; SEVERE, 400 kdyn contusion; SHAM) and combined standard echocardiography with speckle tracking analyses to investigate in vivo cardiac function and deformation (contractility) after experimental SCI in the Wistar rat. In addition, we investigated changes in the intrinsic structure of cardiac myocytes ex vivo. We demonstrate that SEVERE SCI induces a characteristic decline in LV chamber size and a reduction in in vivo LV deformation (i.e. radial strain) throughout the entire systolic portion of the cardiac cycle [25.6 ± 3.0 versus 44.5 ± 8.1% (Pre-injury); P = 0.0029]. SEVERE SCI also caused structural changes in cardiomyocytes, including decreased length [115.6 ± 7.63 versus 125.8 ± 6.75 μm (SHAM); P = 0.0458], decreased width [7.78 ± 0.71 versus 10.78 ± 1.08 μm (SHAM); P = 0.0015] and an increase in the length/width ratio [14.88 ± 0.66 versus 11.74 ± 0.89 (SHAM); P = 0.0018], which was significantly correlated with LV flow-generating capacity after SCI (i.e. stroke volume, R²  = 0.659; P = 0.0013). Rats with MODERATE SCI exhibited no changes in any metric versus SHAM. This is the first study to demonstrate that the severity of SCI determines the course of changes in the intrinsic structure of cardiomyocytes, which are directly related to contractile function of the LV.