Applanation tonometry: a reliable technique to assess aortic pulse wave velocity in spinal cord injury

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.

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.

Increased pulse wave velocity in persons with spinal cord injury: the effect of the renin-angiotensin-aldosterone system

Increased pulse wave velocity (PWV), a marker of cardiovascular disease (CVD), has been reported in otherwise healthy individuals with spinal cord injury (SCI) compared with age-matched uninjured controls. Due to decentralized descending sympathetic vascular control, individuals with injuries above T6 are prone to orthostatic hypotension and, as a result, depend on the renin-angiotensin-aldosterone system (RAAS) to maintain orthostatic blood pressure (BP). The purpose of this study was to determine resting PWV, a noninvasive surrogate of central arterial stiffness, in individuals with cervical (C4-T1; n = 11) and thoracic (T6-T12; n = 11) SCI, compared with age-matched controls (controls; n = 11). Next, our aim was to describe group differences in BP, plasma norepinephrine (NE), and renin response to head-up tilt (HUT). Finally, we sought to determine the relationship between PWV and the orthostatic change in BP, NE, and the plasma renin during HUT among the groups. PWV was significantly increased in both cervical (8.81 ± 1.91 m/s) and thoracic (7.36 ± 1.58 m/s) SCI compared with the controls (5.53 ± 0.95 m/s; P < 0.05). The change from supine to 60° HUT in BP and NE was significantly reduced and change in plasma renin was significantly increased in the cervical group compared with the thoracic and control groups. Group affiliation and change in plasma renin were significant predictors of PWV (R² = 0.63, P = 0.001). These data suggest that dependency on the RAAS for orthostatic BP maintenance may be associated with increased PWV and risk of CVD in the SCI population.NEW & NOTEWORTHY Our novel findings suggest that increased arterial stiffness in individuals with SCI may be due to greater dependency on the RAAS to maintain hemodynamic stability during an orthostatic challenge. Asymptomatic orthostatic hypotension can occur in persons with SCI during transition from the supine to the seated position and during other upright activities of daily living; however, it is seldom addressed by clinicians.

Effects of exercise interventions on cardiovascular health in individuals with chronic, motor complete spinal cord injury: protocol for a randomised controlled trial [Cardiovascular Health/Outcomes: Improvements Created by Exercise and education in SCI (CHOICES) Study]

INTRODUCTION

Recent studies demonstrate that cardiovascular diseases and associated complications are the leading cause of morbidity and mortality in individuals with spinal cord injury (SCI). Abnormal arterial stiffness, defined by a carotid-to-femoral pulse wave velocity (cfPWV) ≥10 m/s, is a recognised risk factor for heart disease in individuals with SCI. There is a paucity of studies assessing the efficacy of conventional training modalities on arterial stiffness and other cardiovascular outcomes in this population. Therefore, this study aims to compare the efficacy of arm cycle ergometry training (ACET) and body weight-supported treadmill training (BWSTT) on reducing arterial stiffness in individuals with chronic motor complete, high-level (above the sixth thoracic segment) SCI.

METHODS AND ANALYSIS

This is a multicentre, randomised, controlled, clinical trial. Eligible participants will be randomly assigned (1:1) into either ACET or BWSTT groups. Sixty participants with chronic (>1 year) SCI will be recruited from three sites in Canada (Vancouver, Toronto and Hamilton). Participants in each group will exercise three times per week up to 30 min and 60 min for ACET and BWSTT, respectively, over the period of 6 months. The primary outcome measure will be change in arterial stiffness (cfPWV) from baseline. Secondary outcome measures will include comprehensive assessments of: (1) cardiovascular parameters, (2) autonomic function, (3) body composition, (4) blood haematological and metabolic profiles, (5) cardiorespiratory fitness and (6) quality of life (QOL) and physical activity outcomes. Outcome measures will be assessed at baseline, 3 months, 6 months and 12 months (only QOL and physical activity outcomes). Statistical analyses will apply linear-mixed modelling to determine the training (time), group (ACET vs BWSTT) and interaction (time × group) effects on all outcomes.

ETHICS AND DISSEMINATION

Ethical approval was obtained from all three participating sites. Primary and secondary outcome data will be submitted for publication in peer-reviewed journals and widely disseminated.

TRIAL REGISTRATION NUMBER

NCT01718977; Pre-results.

TRIAL STATUS

Recruitment for this study began on January 2013 and the first participant was randomized on April 2013. Recruitment stopped on October 2018.

Physical exercise improves arterial stiffness after spinal cord injury

OBJECTIVE/BACKGROUND

Aortic pulse wave velocity (PWV), the gold-standard assessment of central arterial stiffness, has prognostic value for cardiovascular disease risk in able-bodied individuals. The aim of this study was to compare aortic PWV in athletes and non-athletes with spinal cord injury (SCI).

DESIGN

Cross-sectional comparison.

METHODS

Aortic PWV was assessed in 20 individuals with motor-complete, chronic SCI (C2-T5; 18 ± 8 years post-injury) using applanation tonometry at the carotid and femoral arterial sites. Ten elite hand-cyclists were matched for sex to 10 non-athletes; age and time since injury were comparable between the groups. Heart rate and discrete brachial blood pressure measurements were collected throughout testing.

OUTCOME MEASURES

Aortic PWV, blood pressure, heart rate.

RESULTS

Aortic PWV was significantly lower in athletes vs. non-athletes (6.9 ± 1.0 vs. 8.7 ± 2.5 m/second, P = 0.044). There were no significant between-group differences in resting supine mean arterial blood pressure (91 ± 19 vs. 81 ± 10 mmHg) and heart rate (60 ± 10 vs. 58 ± 6 b.p.m.).

CONCLUSION

Athletes with SCI exhibited improved central arterial stiffness compared to non-athletes, which is in agreement with the previous able-bodied literature. This finding implies that chronic exercise training may improve arterial health and potentially lower cardiovascular disease risk in the SCI population.

Exploring the associations between arterial stiffness and spinal cord impairment: A cross-sectional study

BACKGROUND/OBJECTIVE

Elevated aortic arterial stiffness (aortic pulse wave velocity: aPWV) is an independent coronary artery disease predictor among the general population. The purpose of this study was to: (1) report aPWV values in a representative cohort of patients with spinal cord injury (SCI); (2) to compare aPWV values in people with SCI based on neurological level of injury; and (3) to contrast the reported aPWV values with available normal values for the general population.

METHODS

Adults with chronic SCI (n = 87) were divided into two groups (TETRA group, n = 37 and PARA group, n = 50). aPWV and potential confounders of aPWV were assessed. Analysis of covariance was used for comparisons between groups and adjusted for the confounders. Subjects' aPWV values were contrasted with reference values for general population determined by "The Reference value for arterial stiffness' collaboration" and prevalence of abnormal aPWV defined as greater than or equal to the age-specific 90th percentile was reported.

RESULTS

Prevalence of abnormal aPWV in the cohort was 25.3%. After adjusting for covariates, the mean aPWV values were significantly different between two groups (TETRA: 8.0 (95% confidence interval (CI): 7.5-8.6) m/second, PARA: 9.0 (95% CI: 8.5-9.4) m/second, P = 0.010). The prevalence of abnormal aPWV was significantly higher in the PARA group (36%) compared to the TETRA group (11%) (P = 0.012).

CONCLUSIONS

One-quarter of the total cohort had an abnormal aPWV. Subjects with paraplegia had higher aPWV values and a higher frequency of abnormal aPWV than subjects with tetraplegia. Elevated aPWV in people with SCI, particularly those with paraplegia, may impart significant adverse cardiovascular consequences.

Microflotronic arterial tonometry for continuous wearable non-invasive hemodynamic monitoring

Personalized mobile medicine will continue to advance through the development of wearable sensors that can wirelessly provide pertinent health information while remaining unobtrusive, comfortable, low cost, and easy to operate and interpret. It is the intention that the sensor presented hereafter can contribute to such innovation. By applying a combination of emerging microfluidic and electronic technologies, a miniature, flexible, transparent, highly sensitive and wearable pressure sensor with microfluidic elements has been implemented, referred to as a microflotronic device. High sensitivity of 0.1 kPa(-1) and fast response time on the order of tens of milliseconds has been achieved on the microflotronic sensor design. Its sensitivity is among the highest in impedance-based flexible pressure sensors. Once configured into an array, the transparent device can be easily aligned over the target artery to measure blood pressure noninvasively and continuously. In addition, the ultraflexible and thin plastic construct of the microflotronic sensor (of 270 µm in height) can be worn comfortably for extended periods of time. Importantly, the proposed microflotronic sensor has been utilized to perform arterial tonometry with the capability of noninvasive monitoring of arterial blood pressure waveforms in a real-time and continuous fashion.