Benditt D G, Chen M Y, Hansen R, Buetikofer J, Lurie K
Department of Medicine, University of Minnesota, Minneapolis.
J Am Coll Cardiol. 1995 Jan;25(1):70-5. doi: 10.1016/0735-1097(94)00348-t.
This study aimed to characterize subcutaneous blood flow changes during neurally mediated syncope and to determine whether microvasculature oscillation (vasomotion) is characteristically altered in conjunction with syncopal events.
Marked pallor is commonly associated with neurally mediated syncope. However, little attention has been paid to the evaluation of subcutaneous blood flow and vasomotion in this setting.
This study utilized laser Doppler flowmetry to assess changes in subcutaneous microvascular blood flow during head-up tilt table testing in 13 patients with syncope and 6 control subjects. Blood flow and vasomotion frequency were measured continuously before, during and after completion of 80 degrees head-up tilt testing (< or = 25-min duration).
Among the 13 patients with syncope, tilt testing reproduced syncopal symptoms in 9 (tilt-positive group) but not in 4 (tilt-negative group). None of the six control subjects developed symptoms during testing. Baseline mean subcutaneous blood flow did not differ significantly among the three groups. However, during upright tilt, blood flow gradually diminished in the tilt-positive group, reaching a nadir of 0.8 +/- 0.33 ml/min per 100 g of tissue (mean +/- SD), but remained relatively constant in the tilt-negative group and control subjects. The difference in mean blood flow response to tilt was statistically significant when the tilt-positive group was compared with either the tilt-negative group or control subjects (p < 0.001). Similarly, baseline blood flow oscillation frequency did not differ significantly in the three subgroups (tilt-positive group 0.2 +/- 0.11 Hz; tilt-negative group 0.2 +/- 0.02 Hz; control subjects 0.2 +/- 0.11 Hz). Subsequently, during tilt testing only the tilt-positive group exhibited increased oscillation frequency; oscillation frequency remained essentially constant throughout the tilt test in the tilt-negative group and control subjects (p < 0.001, tilt-positive group vs. either the tilt-negative group or control subjects).
These findings document an expected diminution of subcutaneous blood flow in association with neurally mediated syncope and indicate that characteristic changes in microvasculature oscillation frequency occur in conjunction with syncopal symptoms. To the extent that microvasculature vasomotion is influenced by neural control, the changes in vasomotion frequency are consistent with relative diminution of peripheral sympathetic neural influence during neurally mediated syncopal episodes.
本研究旨在描述神经介导性晕厥期间皮下血流变化特征，并确定微血管振荡（血管运动）是否会伴随晕厥事件发生特征性改变。
显著苍白通常与神经介导性晕厥相关。然而，在此情况下对皮下血流和血管运动的评估关注较少。
本研究利用激光多普勒血流仪评估13例晕厥患者和6例对照者在头高位倾斜试验期间皮下微血管血流变化。在80度头高位倾斜试验（持续时间≤25分钟）前、试验期间及试验结束后连续测量血流和血管运动频率。
13例晕厥患者中，9例（倾斜试验阳性组）倾斜试验重现了晕厥症状，4例（倾斜试验阴性组）未重现。6例对照者在试验期间均未出现症状。三组间基线平均皮下血流无显著差异。然而，在直立倾斜过程中，倾斜试验阳性组血流逐渐减少，降至最低点0.8±0.33毫升/分钟/100克组织（平均值±标准差），而倾斜试验阴性组和对照者血流保持相对稳定。将倾斜试验阳性组与倾斜试验阴性组或对照者相比，倾斜时平均血流反应差异有统计学意义（p<0.001）。同样，三个亚组基线血流振荡频率无显著差异（倾斜试验阳性组0.2±0.11赫兹；倾斜试验阴性组0.2±0.02赫兹；对照者0.2±0.11赫兹）。随后，在倾斜试验期间，仅倾斜试验阳性组振荡频率增加；倾斜试验阴性组和对照者在整个倾斜试验过程中振荡频率基本保持不变（p<0.001，倾斜试验阳性组与倾斜试验阴性组或对照者相比）。
这些发现证明了与神经介导性晕厥相关的皮下血流预期减少，并表明微血管振荡频率的特征性改变与晕厥症状同时出现。就微血管血管运动受神经控制而言，血管运动频率的变化与神经介导性晕厥发作期间外周交感神经影响的相对减少一致。
