Phillips Aaron A, Krassioukov Andrei V, Ainslie Philip N, Cote Anita T, Warburton Darren E R
1 Cardiovascular Physiology and Rehabilitation Laboratory , Physical Activity Promotion and Chronic Disease Prevention Unit, University of British Columbia , Vancouver, Canada .
J Neurotrauma. 2014 Jun 15;31(12):1122-8. doi: 10.1089/neu.2013.3280. Epub 2014 May 13.
After cervical spinal cord injury (SCI), orthostatic hypotension and intolerance commonly ensue. The cardiovagal baroreflex plays an important role in the acute regulation of blood pressure (BP) and is associated with the onset of presyncope. The cardiovagal baroreflex is dysfunctional after SCI; however, this may be influenced by either increased stiffening of the arteries containing the stretch-receptors (which has been shown in SCI) or a more downstream neural mechanism (i.e., solitary nucleus, sinoatrial node). Identifying where along this pathway baroreflex dysfunction occurs may highlight a potential therapeutic target. This study examined the relationship between spontaneous cardiovagal baroreflex sensitivity (BRS) and common carotid artery (CCA) stiffness in those with high level SCI before and after midodrine (alpha1-agonist) administration, as well as in able-bodied controls, to evaluate: (1) the role arterial stiffening plays mediating baroreflex function after SCI and (2) the effect of normalizing BP on these parameters. Three to five min recordings of beat-by-beat BP and heart rate, as well as 30 sec duration recordings of CCA diameter were used for analysis. All participants were tested supine and during upright-tilt. Arterial stiffness (β-stiffness index) was elevated in those with SCI when upright (+12%; p<0.05). Further, β-stiffness index was negatively related to reduced BRS in those with SCI when upright (R2=0.55; p<0.05), but not in able-bodied persons. Normalizing BP did not improve BRS or CCA stiffness. This study clearly shows that reduced BRS is closely related to increased arterial stiffness in the population with SCI.
颈脊髓损伤（SCI）后，常出现体位性低血压和不耐受。心迷走压力反射在血压（BP）的急性调节中起重要作用，并与晕厥前期的发作有关。SCI后心迷走压力反射功能失调；然而，这可能受含有牵张感受器的动脉僵硬程度增加（已在SCI中得到证实）或更下游的神经机制（即孤束核、窦房结）的影响。确定压力反射功能障碍在该通路的发生部位可能会突出潜在的治疗靶点。本研究检测了米多君（α1激动剂）给药前后高位SCI患者以及健康对照者的自发性心迷走压力反射敏感性（BRS）与颈总动脉（CCA）僵硬度之间的关系，以评估：（1）动脉僵硬在SCI后介导压力反射功能中所起的作用；（2）血压正常化对这些参数的影响。逐搏血压和心率的3至5分钟记录以及CCA直径的30秒记录用于分析。所有参与者均在仰卧位和直立倾斜时进行测试。SCI患者直立时动脉僵硬度（β僵硬度指数）升高（+12%；p<0.05）。此外，SCI患者直立时β僵硬度指数与降低的BRS呈负相关（R2=0.55；p<0.05），而健康人则无此相关性。血压正常化并未改善BRS或CCA僵硬度。本研究清楚地表明，在SCI人群中，降低的BRS与动脉僵硬度增加密切相关。
