AIMS:Competitive flow from native coronary vessels is considered a major factor in the failure of coronary bypass grafts. However, the pathophysiological effects are not fully understood. Low and oscillatory wall shear stress (WSS) is known to induce endothelial dysfunction and vascular disease, like atherosclerosis and intimal hyperplasia. The aim was to investigate the impact of competitive flow on WSS in mammary artery bypass grafts. METHODS AND RESULTS:Using computational fluid dynamics, WSS was calculated in a left internal mammary artery (LIMA) graft to the left anterior descending artery in a three-dimensional in vivo porcine coronary artery bypass graft model. The following conditions were investigated: high competitive flow (non-significant coronary lesion), partial competitive flow (significant coronary lesion), and no competitive flow (totally occluded coronary vessel). Time-averaged WSS of LIMA at high, partial, and no competitive flow were 0.3-0.6, 0.6-3.0, and 0.9-3.0 Pa, respectively. Further, oscillatory WSS quantified as the oscillatory shear index (OSI) ranged from (maximum OSI = 0.5 equals zero net WSS) 0.15 to 0.35, <0.05, and <0.05, respectively. Thus, high competitive flow resulted in substantial oscillatory and low WSS. Moderate competitive flow resulted in WSS and OSI similar to the no competitive flow condition. CONCLUSION:Graft flow is highly dependent on the degree of competitive flow. High competitive flow was found to produce unfavourable WSS consistent with endothelial dysfunction and subsequent graft narrowing and failure. Partial competitive flow, however, may be better tolerated as it was found to be similar to the ideal condition of no competitive flow.

译文

目的:来自天然冠状血管的竞争性血流被认为是造成冠状动脉搭桥术失败的主要因素。但是,尚未完全了解其病理生理作用。低而振荡的壁切应力(WSS)会引起内皮功能障碍和血管疾病,例如动脉粥样硬化和内膜增生。目的是研究竞争流量对乳动脉旁路移植术中WSS的影响。
方法和结果:利用计算流体动力学,在三维体内猪冠状动脉旁路移植模型中,在左乳内动脉(LIMA)移植到左前降支中计算WSS。研究了以下情况:高竞争流量(非重大冠状动脉病变),部分竞争流量(重大冠状动脉病变)和无竞争流量(完全阻塞冠状动脉)。 LIMA在高流量,部分流量和无竞争流量下的时间平均WSS分别为0.3-0.6、0.6-3.0和0.9-3.0 Pa。此外,量化为振荡剪切指数(OSI)的振荡WSS分别在(最大OSI = 0.5等于零净WSS)0.15至0.35,<0.05和<0.05的范围内。因此,高竞争流量导致大量振荡和低WSS。中等竞争流量导致WSS和OSI类似于无竞争流量情况。
结论:移植物的流动高度依赖于竞争性流动的程度。发现高竞争流量产生不利的WSS,其与内皮功能障碍以及随后的移植物变窄和衰竭一致。但是,部分竞争性流可能被更好地容忍,因为它被发现与没有竞争性流的理想条件相似。

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