Caiani E G, Weinert L, Takeuchi M, Veronesi F, Sugeng L, Corsi C, Capderou A, Cerutti S, Vaïda P, Lang R M
Dipartimento di Bioingegneria, Politecnico di Milano, Milan, Italy.
J Appl Physiol (1985). 2007 Jul;103(1):80-7. doi: 10.1152/japplphysiol.00625.2006.
We tested the hypothesis that in normal subjects, cardiac tissue velocities, strain, and strain rates (SR), measured by Doppler tissue echocardiography (DTE), are preload dependent. To accomplish it, immediately preceding image acquisition, reversible, repeatable, acute nonpharmacological changes in preload were induced by parabolic flight. DTE has been proposed as a new approach to assess left ventricular regional myocardial function by computing tissue velocities, strain, and SR. However, preload dependence of these parameters in normal subjects still remains controversial. DTE images (Philips) were obtained in 10 normal subjects in standing upright position at normogravity (1 Gz), hypergravity (1.8 Gz), and microgravity (0 Gz) with and without -50 mmHg lower body negative pressure (LBNP). Myocardial velocity curves in the basal interventricular septum were reconstituted offline from DTE images, from which peak systolic (S'), early (E') and late (A') diastolic velocities, SR, and peak systolic strain (PSepsilon) were measured and averaged over four beats. At 1.8 Gz (reduced venous return), S', E', and A' decreased by 21%, 21%, and 26%, respectively, compared with 1-Gz values, while at 0 Gz (augmented venous return), E', A', and PSepsilon increased by 57%, 53%, and 49%, respectively. LBNP reduced E' and PSepsilon. In conclusion, our results were in agreement with those obtained in animal models, in which preload was changed in a controlled, acute, and reversible manner, and image acquisition was performed immediately following preload modifications. The hypothesis of preload dependence was confirmed for S', E', A', and PSepsilon, while SR appeared to be preload independent, probably reflecting intrinsic myocardial properties.
在正常受试者中，通过多普勒组织超声心动图（DTE）测量的心脏组织速度、应变和应变率（SR）依赖于前负荷。为实现这一点，在图像采集前即刻，通过抛物线飞行诱导前负荷发生可逆、可重复的急性非药物性变化。DTE已被提议作为一种通过计算组织速度、应变和SR来评估左心室局部心肌功能的新方法。然而，这些参数在正常受试者中对前负荷的依赖性仍存在争议。在10名正常受试者处于正常重力（1 Gz）、超重（1.8 Gz）和微重力（0 Gz）状态下，分别在有和没有-50 mmHg下肢负压（LBNP）的情况下，获取飞利浦DTE图像。从DTE图像离线重建室间隔基底段的心肌速度曲线，测量其中的收缩期峰值（S'）、舒张早期（E'）和舒张晚期（A'）速度、SR以及收缩期峰值应变（PSepsilon），并在四个心动周期中进行平均。在1.8 Gz（静脉回流减少）时，与1-Gz值相比，S'、E'和A'分别降低了21%、21%和26%，而在0 Gz（静脉回流增加）时，E'、A'和PSepsilon分别增加了57%、53%和49%。LBNP降低了E'和PSepsilon。总之，我们的结果与在动物模型中获得的结果一致，在动物模型中，前负荷以可控、急性和可逆的方式改变，并在负荷改变后立即进行图像采集。前负荷依赖性的假设在S'、E'、A'和PSepsilon方面得到证实，而SR似乎不依赖于前负荷，这可能反映了心肌的内在特性。
