Sharif Hisham, Cotie Lisa M, La Fountaine Michael F, Ditor David S
Department of Kinesiology, Brock University, 500 Glenridge Avenue, St. Catharines, Ontario ON L2S 3A1, Canada.
Department of Physical Therapy, Seton Hall University, South Orange, NJ, USA; VA RR&D National Center of Excellence for the Medical Consequences of Spinal Cord Injury, Bronx, NY, USA.
Auton Neurosci. 2015 Jul;190:46-52. doi: 10.1016/j.autneu.2015.04.002. Epub 2015 Apr 20.
To investigate, via autonomic blockade, if the QT-variability index (QTVI) is a measure of cardiac autonomic regulation in able-bodied (AB) and incomplete spinal cord injured (SCI) individuals.
Four SCI (41.6±13.4years; C4-C7, AIS B-D, 13.4±13.4years post injury) and 4 AB (33.0±7.8years) individuals were tested. QTVI was determined from electrocardiographic readings obtained during supine rest and cardiovascular (CV) stress, with and without autonomic blockade. CV stress was induced by 40° head-up tilt, the hand submerged in 10°C water and the jaw clenched. Autonomic blockade was achieved with metoprolol (β-blockade) and atropine (cholinergic blockade).
There was no group×condition interaction for QTVI, although there was a significant main effect for condition. After collapsing across groups, QTVI increased with CV stress (p=0.01) and decreased with subsequent β-blockade (p=0.04), suggesting that during CV stress, QTVI is reflective of cardiac sympathetic activity. During supine rest, β-blockade did not change QTVI (p=0.24), however, cholinergic blockade increased QTVI (p<0.001), suggesting that during rest, QTVI is inversely related to cardiac parasympathetic regulation.
During times of CV stress, QTVI reflects cardiac sympathetic activity, while during resting conditions, QTVI is inversely related to cardiac parasympathetic activity. These relationships persist after autonomically incomplete SCI.
通过自主神经阻滞，研究QT变异性指数（QTVI）是否可作为健全个体（AB）和不完全性脊髓损伤（SCI）个体心脏自主神经调节的一种测量指标。
对4名脊髓损伤患者（年龄41.6±13.4岁；损伤平面C4 - C7，美国脊髓损伤协会损伤分级B - D级，受伤后13.4±13.4年）和4名健全个体（年龄33.0±7.8岁）进行测试。QTVI通过仰卧休息和心血管（CV）应激期间获得的心电图读数来确定，分别在有和没有自主神经阻滞的情况下进行。CV应激通过40°头高位倾斜、手浸入10°C水中和咬紧牙关来诱发。使用美托洛尔（β受体阻滞）和阿托品（胆碱能阻滞）实现自主神经阻滞。
尽管条件存在显著主效应，但QTVI不存在组×条件交互作用。合并各小组后，QTVI随CV应激增加（p = 0.01），随后随β受体阻滞而降低（p = 0.04），这表明在CV应激期间，QTVI反映心脏交感神经活动。在仰卧休息期间，β受体阻滞未改变QTVI（p = 0.24），然而，胆碱能阻滞增加了QTVI（p < 0.001），这表明在休息期间，QTVI与心脏副交感神经调节呈负相关。
在CV应激期间，QTVI反映心脏交感神经活动，而在休息状态下，QTVI与心脏副交感神经活动呈负相关。这些关系在自主神经功能未完全恢复的脊髓损伤后依然存在。
