Gamble G, Zorn J, Sanders G, MacMahon S, Sharpe N
Department of Medicine, University of Auckland, New Zealand.
Stroke. 1994 Jan;25(1):11-6. doi: 10.1161/01.str.25.1.11.
Arterial stiffness may indicate early vascular changes that predispose to the development of major vascular disease. The repeatability of a variety of indices of arterial stiffness calculated from a standard carotid arterial M-mode ultrasound image was investigated.
Twenty-six asymptomatic normal subjects were imaged and had blood pressure recordings on each of two separate occasions at least 1 day apart. Using a computer-assisted method, the maximum and minimum internal diameter and average wall thickness of the right common carotid artery were measured over several cardiac cycles, and the following indices of arterial stiffness and distensibility (compliance) were derived: the pressure-strain elastic modulus (Ep), Young's modulus (E), cross-sectional compliance (CC), and the distensibility coefficient (DC).
The repeatability of these measures, expressed as coefficients of variation, was as follows: Ep, 18%; E, 24%; CC, 14%; and DC, 13%. In another group of 20 subjects, the coefficient of variation for repeat examination by different sonographers was Ep, 19%; E, 20%; CC, 14%; and DC, 17% and for the one sonographer using two ultrasound machines was Ep, 13%; E, 13%; CC, 11%; and DC, 13%. These values indicate a moderate level of repeatability. In a univariate analysis each of these indices was significantly related to increasing age (Ep = 1.0 + 12.9 x AGE, r = .80; E = 314.5 + 13.9 x AGE, r = .48; CC = 22.6-0.26 x AGE, r = -.63; DC = 64.0-0.65 x AGE, r = -.78) but not to wall thickness (all P > .47). Using multiple regression techniques to adjust for age, wall thickness is a significant predictor of distensibility (P = .017), cross-sectional compliance (P < .001), and the pressure-strain elastic modulus (P = .019). Because Young's modulus is calculated from wall thickness, it could not be included in the multivariate analysis.
We conclude that estimates of carotid artery distensibility and cross-sectional compliance derived from M-mode ultrasound recordings are moderately repeatable and may provide useful additional end points for trials of atherosclerotic progression.
动脉僵硬度可能预示着早期血管变化，这些变化易引发主要血管疾病。本研究调查了从标准颈动脉M型超声图像计算得出的多种动脉僵硬度指标的可重复性。
对26名无症状正常受试者进行成像，并在至少间隔1天的两个不同时间分别记录血压。使用计算机辅助方法，在多个心动周期内测量右侧颈总动脉的最大和最小内径以及平均壁厚度，并得出以下动脉僵硬度和扩张性（顺应性）指标：压力应变弹性模量（Ep）、杨氏模量（E）、横截面积顺应性（CC）和扩张系数（DC）。
这些测量指标的可重复性以变异系数表示如下：Ep为18%；E为2�%；CC为14%；DC为13%。在另一组20名受试者中，不同超声检查人员重复检查的变异系数为：Ep为19%；E为20%；CC为14%；DC为17%；而同一超声检查人员使用两台超声机器的变异系数为：Ep为13%；E为13%；CC为11%；DC为13%。这些值表明可重复性处于中等水平。在单变量分析中，这些指标中的每一个都与年龄增长显著相关（Ep = 1.0 + 12.9×年龄，r = 0.80；E = 314.5 + 13.9×年龄，r = 0.48；CC = 22.6 - 0.26×年龄，r = -0.63；DC = 64.0 - 0.65×年龄，r = -0.78），但与壁厚度无关（所有P > 0.47）。使用多元回归技术对年龄进行校正后，壁厚度是扩张性（P = 0.017）、横截面积顺应性（P < 0.001）和压力应变弹性模量（P = 0.019）的显著预测指标。由于杨氏模量是根据壁厚度计算得出的，因此无法纳入多变量分析。
我们得出结论，从M型超声记录得出的颈动脉扩张性和横截面积顺应性估计值具有中等可重复性，可能为动脉粥样硬化进展试验提供有用的额外终点指标。
