Fillinger M F, Cronenwett J L, Besso S, Walsh D B, Zwolak R M
Section of Vascular Surgery, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756.
J Vasc Surg. 1994 Jun;19(6):970-8; discussion 978-9. doi: 10.1016/s0741-5214(94)70208-x.
Although arteries appear to remodel in response to changes in hemodynamic parameters such as shear stress, little is known about functioning human vein grafts. This study was designed to explore diameter changes in human saphenous vein grafts after infrainguinal bypass.
We used duplex ultrasonography to measure hemodynamic variables that might affect the diameter of 48 in situ saphenous vein grafts during the first year after infrainguinal arterial bypass. Volumetric flow rate, average velocity, peak systolic velocity, and vein diameter in the proximal and distal thirds of these grafts were each measured at 1 week and at 3, 6, and 12 months after operation. Veins were divided into three groups based on initial size (1 week after bypass) in the below-knee segment: small, < 3.5 mm diameter; medium, 3.5 to 4 mm diameter; and large, > 4 mm diameter.
Distal vein diameters at 1 week for small, medium, and large grafts were 2.9 +/- 0.1, 3.7 +/- 0.1, and 4.3 +/- 0.1 mm, respectively (p < 0.001), but by 12 months these diameters were 3.6 +/- 0.2, 3.8 +/- 0.2, and 3.9 +/- 0.2 mm, respectively (p = 0.54). Large veins decreased in diameter, whereas small veins increased in diameter, as confirmed by linear regression of percent change in diameter versus initial vein graft diameter (r = -0.62, p < 0.001). Volumetric flow rate, peak systolic velocity, and shear stress also tended to approach uniform values over time. Of the hemodynamic variables studied, the best predictor of diameter change was shear stress (linear regression of percent change in diameter vs shear stress, r = 0.67, p < 0.001). Veins with a diameter increase greater than 10% over time had significantly higher initial shear stress than veins with a diameter decrease greater than 10% over time (28.6 +/- 3.8 vs 13.1 +/- 1.8 dynes/cm2, p < 0.01), whereas initial volumetric flow rates in these two groups were similar (135 +/- 23 vs 130 +/- 15 ml/min).
Infrainguinal in situ vein graft diameter, volume flow rate, peak systolic velocity, and shear stress all tend to stabilize at uniform values regardless of the initial vein graft diameter. Of the hemodynamic variables studied, shear stress is most strongly associated with the change in diameter over time. Thus human saphenous vein appears to be capable of adapting to its hemodynamic environment after arterial grafting by modulating diameter to normalize shear stress.
尽管动脉似乎会根据诸如剪切应力等血流动力学参数的变化进行重塑，但对于人体静脉移植物的功能了解甚少。本研究旨在探讨腹股沟下旁路术后人体大隐静脉移植物的直径变化。
我们使用双功超声测量了48条原位大隐静脉移植物在腹股沟下动脉旁路术后第一年可能影响其直径的血流动力学变量。在术后1周以及3、6和12个月时，分别测量这些移植物近端和远端三分之一处的容积流量、平均速度、收缩期峰值速度和静脉直径。根据膝下段初始大小（旁路术后1周）将静脉分为三组：小，直径<3.5 mm；中，直径3.5至4 mm；大，直径>4 mm。
小、中、大移植物在1周时的远端静脉直径分别为2.9±0.1、3.7±0.1和4.3±0.1 mm（p<0.001），但到12个月时，这些直径分别为3.6±0.2、3.8±0.2和3.9±0.2 mm（p = 0.54）。通过直径变化百分比与初始静脉移植物直径的线性回归证实，大静脉直径减小，而小静脉直径增加（r = -0.62，p<0.001）。随着时间的推移，容积流量、收缩期峰值速度和剪切应力也趋于接近统一值。在所研究的血流动力学变量中，直径变化的最佳预测指标是剪切应力（直径变化百分比与剪切应力的线性回归，r = 0.67，p<0.001）。随着时间推移直径增加大于10%的静脉，其初始剪切应力显著高于直径减小大于10%的静脉（28.6±3.8对13.1±1.8达因/平方厘米，p<0.01），而这两组的初始容积流量相似（135±23对130±15毫升/分钟）。
无论初始静脉移植物直径如何，腹股沟下原位静脉移植物的直径、容积流量、收缩期峰值速度和剪切应力都倾向于稳定在统一值。在所研究的血流动力学变量中，剪切应力与直径随时间的变化最密切相关。因此，人体大隐静脉在动脉移植后似乎能够通过调节直径来使剪切应力正常化，从而适应其血流动力学环境。
