Theme and aims: Coronary arteries have high curvatures, and hence flow through them causes disturbed flow patterns, resulting in stenosis and atherosclerosis. This in turn decreases the myocardial flow perfusion, causing myocardial ischemia and infarction. Therefore, in order to understand the mechanisms of these phenomena caused by high curvatures and branching of coronary arteries, we have conducted elaborate hemodynamic analysis for both (i) idealized coronary arteries with geometrical parameters representing curvatures and stenosis, and (ii) patient-specific coronary arteries with stenoses.

Methods and results: Firstly, in idealized coronary arteries with approximated realistic arterial geometry representative of their curvedness and stenosis, we have computed the hemodynamic parameters of pressure drop, wall shear stress (WSS) and wall pressure gradient (WPG), and their association with the geometrical parameters of curvedness and stenosis. Then, we have determined the wall shear stress and wall pressure gradient distributions in four patient-specific curved stenotic right coronary arteries (RCAs), that were reconstructed from medical images of patients diagnosed with atherosclerosis and stenosis, as illustrated in Figure 1, in which the locations of the stenoses are highlighted by arrows.

Figure 1: Three-dimensional CT visualization of arteries in patients with suspected coronary disease. The arteries can be seen as a combination of various curved segments with stenoses at unspecific locations highlighted by arrows.

Our results show high WSS and WPG regions at the stenoses and inner wall of the arterial curves, as depicted in Figure 2. Therein, the encapsulations show (i) high WSS, and (ii) high WPG regions at the stenosis and inner wall of the arterial curves.

Figure 2: WSS and WPG surface plot of realistic arteries (a), (b), (c) and (d), wherein the small squared parts are enlarged to show the detailed localized contour plots at the stenotic regions. Therein, the circular encapsulations show (i) high WSS and (ii) high WPG regions at the stenosis and inner wall of the arterial curves.

Conclusion and novelty: This paper provides useful insights into the causative mechanisms of the high incidence of atherosclerosis in coronary arteries. It also provides guidelines for how simulation of blood flow in patient coronary arteries and determination of the hemodynamic parameters of WSS and WPG can provide a medical assessment of the risk of development of atherosclerosis and plaque formation, leading to myocardial ischemia and infarction. The novelty of our paper is our showing how in actual coronary arteries (based on their CT imaging), curvilinearity and narrowing complications affect the computed WSS and WPG associated with risk of atherosclerosis. This is very important for cardiologists to be able to properly take care of their patients and provide remedial measures before coronary complications lead to myocardial infarctions and necessitate stenting or coronary bypass surgery.

主题和目的：冠状动脉弯曲度很高，因此流经它们会导致流动模式紊乱，从而导致狭窄和动脉粥样硬化。反过来，这会减少心肌血流灌注，从而引起心肌缺血和梗塞。因此，为了了解由高弯曲度和冠状动脉分支引起的这些现象的机制，我们对（i）具有代表弯曲度和狭窄的几何参数的理想化冠状动脉，以及（ii）针对患者的特定情况进行了详尽的血液动力学分析冠状动脉狭窄。

方法和结果：首先，在理想的冠状动脉中以近似真实的动脉几何结构代表其弯曲和狭窄，我们计算了压降，壁切应力（WSS）和壁压梯度（WPG）的血液动力学参数，以及它们与弯曲和狭窄的几何参数。然后，我们确定了四个患者特定的弯曲狭窄右冠状动脉（RCA）的壁切应力和壁压梯度分布，这些分布是根据诊断为动脉粥样硬化和狭窄的患者的医学图像重建的，如图1所示。狭窄部位的位置以箭头突出显示。

图1：疑似冠心病患者的动脉三维CT可视化。动脉可以看作是各种弯曲段的组合，在非特定位置用箭头突出显示狭窄。

我们的结果显示，在动脉曲线的狭窄和内壁处有高WSS和WPG区域，如图2所示。其中，包囊显示（i）高WSS和（ii）在狭窄和内壁的WPG高区域。动脉曲线。

图2：真实动脉（a），（b），（c）和（d）的WSS和WPG表面图，其中小方块放大了，以显示狭窄区域的详细局部轮廓图。其中，圆形包囊在动脉曲线的狭窄和内壁处显示（i）高WSS和（ii）高WPG区域。

结论和新颖性：本文为冠状动脉粥样硬化高发的病因机制提供了有用的见解。它还提供了有关如何模拟患者冠状动脉血流以及确定WSS和WPG的血流动力学参数的指南，这些医学指南可对发生动脉粥样硬化和斑块形成，导致心肌缺血和梗塞的风险进行医学评估。本文的新颖之处在于，我们展示了在实际冠状动脉（基于CT成像）中，曲线性和狭窄并发症如何影响与动脉粥样硬化风险相关的WSS和WPG的计算。