Systemic vascular resistance is increased and associated with accelerated arterial stiffening change in patients with chronic cervical spinal cord injury
ABSTRACT BACKGROUND: Despite of stiffening change of conduit arteries, how total peripheral resistance (TPR) is adapted to chronic spinal cord injury (SCI) remains unclear. AIM: To investigate how chronic cervical SCI influences hemodynamic characteristics DESIGN: Cross-sectional, case-control study SETTING: Rehabilitation department in the tertiary medical center POPULATION: Twenty-one male patients with traumatic SCI resulting from cervical spine fracture were recruited. The injury occurred three to 289 months (46 months in average) previously. Twenty-one healthy male participants with matched age and body mass index were enrolled as control group. METHODS: The subjects were asked to maintain supine rest (SR) and then head-up tilt (HUT) at 60 degree for five minutes, respectively. A novel noninvasive bio-reactance device was employed to measure cardiac hemodynamics, whereas heart rate variability was used to determine cardiac autonomic activity. Additionally, the digital volume pulse analysis was applied to calculate arterial stiffness index (SI) and arteriolar reflection index (RI). RESULTS: SCI patients revealed less stroke volume and cardiac output (CO), as well as, greater total peripheral resistance (TPR) and SI during SR than normal subjects did. Moreover, the positive correlation between TPR and SI was observed in SCI patients rather than normal subjects. In SCI patients, HUT 1) markedly decreased TPR while CO and cardio-acceleration responses remained intact and 2) decreased HF power value but failed to change LF/HF ratio. Furthermore, the degree of orthostatic hypotension was correlated with the TPRHUT/TPRSR ratio but not the COHUT/COSR ratio. CONCLUSION: Chronic cervical SCI leads to a progressively accelerated increase in vascular stiffness, which is associated with increase in systemic vascular resistance. Furthermore, the cervical SCI-related orthostatic hypotension lies in the impairment of vasoconstriction without cardiac dysfunction. Clinical Rehabilitation Impact. SI, rather than blood pressure, reflects not only cardiovascular risk but also TPR in chronic cervical SCI.
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ABSTRACT: A good estimation of cardiac autonomic modulation is achieved by assessing the heart rate variability (HRV), which represents the variations of the intervals between consecutive normal R wave peaks, usually in the time and frequency domains. In general, a reduced HRV indicates a low vagal activity and, therefore a cardiac autonomic imbalance, which has been associated with aging and with independent and increased risk of different poor outcomes, such as all-cause mortality and sudden cardiac arrest. Since physical activity is an important component of lifestyle and have shown beneficial effects on cardiovascular health, cross-sectional and longitudinal studies have investigated the relationship between physical activity and HRV indices in several age groups. Therefore, the aim of the present chapter is to analyze the current evidence regarding the relationship between HRV indices and physical activity in different age groups. Overall, higher levels of self-reported and objectively measured physical activity are associated with higher HRV. Among young individuals, the levels of moderate-to-vigorous physical activity seem to be strongly associated with a more favorable HRV profile, whereas higher levels of moderate activity appear to be imperative for a higher vagal-related HRV among middle-aged individuals. Among older individuals, it has been reported that besides total leisure-time physical activity, walking pace and distance are prospectively associated with a more favorable HRV profile. Lastly, the mechanisms by which the habitual physical activity could promote changes in the cardiac autonomic modulation are not completely clear, but can be related to improvements in the neurohumoral modulation, for instance, an increase in the nitric oxide bioavailability.Heart Rate Variability (HRV): Prognostic Significance, Risk Factors and Clinical Applications, 1st Edition edited by Shelby Walters, 01/2015: chapter Chapter 3: pages 27-43; Nova Science Publishers, Inc., New York., ISBN: 78-1-63463-736-7
- Edited by Leonora J Mouton, Corien H Plaggenmarsch, Mariella Volkers, Rienk Dekker, Thomas WJ Janssen, Florentina J Hettinga, JHP Houdijk, Sonja de Groot, Lucas HV van der Woude., 04/2015; Wenckebach Instituut, Groningen.