Department of Ocean System Engineering, Jeju National University, Jeju, South Korea.
Ultrasonics. 2014 Jan;54(1):233-40. doi: 10.1016/j.ultras.2013.04.012. Epub 2013 Apr 24.
The geometry of carotid artery bifurcation is of high clinical interest because it determines the characteristics of blood flow that is closely related to the formation and development of atherosclerotic plaque. However, information on the dynamic changes in the vessel wall of carotid artery bifurcation during a pulsatile cycle is limited. This pilot study investigated the cyclic changes in carotid artery geometry caused by blood flow pulsation in rats. A high-resolution ultrasound imaging system with a broadband scanhead centered at 40 MHz was used to obtain longitudinal images of the rat carotid artery. A high frame rate retrospective B-scan imaging technique based on the use of electrocardiogram to trigger signal acquisition was used to examine precisely the fast arterial wall motion. Two-dimensional geometry data obtained from nine rats showed that the rat carotid artery asymmetrically contracts and dilates during each cardiac cycle. Systolic/diastolic vessel diameters near the upstream and downstream regions from the bifurcation were 0.976 ± 0.011/0.825 ± 0.015 mm and 0.766 ± 0.015/0.650 ± 0.016 mm, respectively. Their posterior/anterior wall displacement ratios in the radial direction were 41.0 ± 14.9% and 2.9 ± 1.6%, respectively. These results indicate that in the vicinity of bifurcation, the carotid artery favorably expands to the anterior side during the systolic phase. This phenomenon was observed to be more prominent in the downstream region near the bifurcation. The cyclic variation pattern in wall movement varies depending on the measurement site, which shows different patterns at far upstream and downstream of the bifurcation. The asymmetric radial expansion and contraction of the rat carotid artery observed in this study may be useful in studying the hemodynamic etiology of cardiovascular diseases because the pulsatile changes in vessel geometry may affect the local hemodynamics that determines the spatial distribution of wall shear stress, one of important cardiovascular risk factors. Further systematic study is needed to clarify the effects of wall elasticity, branch angle and vessel diameter ratio on the asymmetric wall motion of carotid artery bifurcation.
颈动脉分叉处的几何形状具有重要的临床意义，因为它决定了血流的特性，而血流与动脉粥样硬化斑块的形成和发展密切相关。然而，关于颈动脉分叉处血管壁在脉动周期内的动态变化的信息有限。这项初步研究调查了血流脉动引起的大鼠颈动脉分叉处几何形状的周期性变化。使用中心频率为 40MHz 的宽带扫描探头的高分辨率超声成像系统获取大鼠颈动脉的纵向图像。使用基于心电图触发信号采集的高帧率回顾性 B 扫描成像技术，可以精确检查快速动脉壁运动。从 9 只大鼠获得的二维几何数据表明，大鼠颈动脉在每个心动周期内不对称地收缩和扩张。分叉处上游和下游区域的收缩/舒张血管直径分别为 0.976±0.011/0.825±0.015mm 和 0.766±0.015/0.650±0.016mm。它们在径向方向上的后/前壁位移比分别为 41.0±14.9%和 2.9±1.6%。这些结果表明，在分叉附近，颈动脉在收缩期有利于向前面扩张。这种现象在分叉处下游附近更为明显。壁运动的循环变化模式取决于测量部位，在分叉的远上游和下游部位表现出不同的模式。本研究中观察到的大鼠颈动脉的不对称径向扩张和收缩可能有助于研究心血管疾病的血流动力学病因，因为血管几何形状的脉动变化可能会影响局部血流动力学，从而决定壁剪切应力的空间分布，壁剪切应力是一个重要的心血管危险因素。需要进一步的系统研究来阐明壁弹性、分支角度和血管直径比对颈动脉分叉处不对称壁运动的影响。
