BMEYE, Academic Medical Center Amsterdam, The Netherlands.
J Hypertens. 2012 May;30(5):932-9. doi: 10.1097/HJH.0b013e3283524932.
Increased large artery stiffness is a major determinant of systolic pressure and indicator of cardiovascular events. The reflected wave, its arrival time (return time) and magnitude, contributes to systolic pressure, and is a supposed indicator of aortic stiffness. With aortic stiffening, the return time is assumed to decrease inversely with PWV as 2L/PWV, where L is the aortic length. However, several studies reported that the inflection point of aortic pressure, a surrogate of return time, varies little with aortic stiffness.
We studied the effects of aortic stiffness on wave reflection in an anatomically accurate arterial model. Return time is time difference of forward, Pf, and backward, Pb, pressure. Return time, inflection and shoulder points, augmentation index, and reflection magnitude (Pb/Pf) were calculated by standard rules.
Peripheral resistance does not affect reflection directly, but only through pressure (stiffness) changes. Magnitude of reflected waves depend about equally on aortic geometry (taper, branches) and distal aortic reflection. Therefore, relations of augmentation index and reflection magnitude with stiffness are nonlinear and complex; augmentation index is most sensitive to stiffness. Between PWV 6 and 12 m/s, representing ages of 20-80 years, return time and inflection and shoulder points change differently with stiffness and PWV cannot be derived from them. Pulse pressure is strongly dependent on aortic stiffness. Taper changes return time by a factor 2, but has little effect on reflection magnitude, augmentation index, and inflection point.
Accurate quantitative information on arterial stiffness cannot be obtained from reflection parameters. The augmentation index is most sensitive to stiffness changes.
大动脉僵硬程度增加是收缩压的主要决定因素，也是心血管事件的指标。反射波及其到达时间（返回时间）和幅度有助于收缩压，并被认为是主动脉僵硬的指标。随着主动脉僵硬，返回时间被认为与 PWV 成反比，即 2L/PWV，其中 L 是主动脉长度。然而，一些研究报告称，主动脉压力的拐点，即返回时间的替代指标，几乎不受主动脉僵硬程度的影响。
我们在一个解剖学准确的动脉模型中研究了主动脉僵硬对波反射的影响。返回时间是正向压力 Pf 和反向压力 Pb 的时间差。返回时间、拐点和肩部点、增强指数和反射幅度（Pb/Pf）是通过标准规则计算的。
外周阻力不会直接影响反射，而是仅通过压力（刚度）变化产生影响。反射波的幅度主要取决于主动脉几何形状（锥形、分支）和远端主动脉反射。因此，增强指数和反射幅度与刚度的关系是非线性和复杂的；增强指数对刚度最敏感。在 PWV 为 6 到 12 米/秒之间，代表 20 到 80 岁的年龄，返回时间和拐点和肩部点随刚度的变化而不同，并且不能从它们中推导出 PWV。脉压强烈依赖于主动脉刚度。锥形变化返回时间的因素为 2，但对反射幅度、增强指数和拐点几乎没有影响。
不能从反射参数中获得动脉僵硬的准确定量信息。增强指数对刚度变化最敏感。
