Blood flow competition after aortic valve bypass: an evaluation using computational fluid dynamics
Blood flow competition after aortic valve bypass: an evaluation using computational fluid dynamics
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DOI：
10.1093/icvts/ivw428
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发表时间：
2017-05-01
影响因子：
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通讯作者：
Misawa, Yoshio
中科院分区：
文献类型：
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作者：
Kawahito, Koji;Kimura, Naoyuki;Misawa, Yoshio
目的：主动脉瓣旁路术（AVB）（心尖-主动脉管道）仍然是外科主动脉瓣置换术或经导管主动脉瓣植入术不可行的患者的有效外科替代方案。然而，特定的并发症包括血栓形成，可能是由顺行和逆行之间的流动竞争引起的停滞引起的，但这尚未得到充分研究。本研究的目的是分析AVB后的流动特性，并阐明使用计算流体力学（CFD）的主动脉内血栓的机制。方法：从一个73岁的术后AVB患者获得的数据进行流动模拟。三维电影相位对比磁共振成像在3特斯拉被用来获取流数据，并建立模拟。使用计算机断层扫描血管造影片重建血管几何结构。在升主动脉和移植物之间的各种流速比下进行流动模拟。结果：CFD显示，当逆行血流占主导地位时，升主动脉弓内存在停滞，表明严重主动脉瓣狭窄和/或左心室功能较差的情况下，升主动脉弓内存在血栓形成的风险。同时，在降主动脉近端的血流停滞时，观察到的顺、逆行流量相当，这表明，降主动脉是关键的主动脉瓣狭窄不严重。结论：在主动脉内的血流停滞，可能会导致血栓时，逆行为主，顺/逆行流量相当。我们的研究结果表明，即使在接受生物瓣膜的患者中，也可能推荐使用抗凝剂。
OBJECTIVES: Aortic valve bypass (AVB) (apico-aortic conduit) remains an effective surgical alternative for patients in whom surgical aortic valve replacement or transcatheter aortic valve implantation is not feasible. However, specific complications include thrombus formation, possibly caused by stagnation arising from flow competition between the antegrade and retrograde flow, but this has not been fully investigated. The aim of this study was to analyse flow characteristics after AVB and to elucidate mechanisms of intra-aortic thrombus using computational fluid dynamics (CFD).METHODS: Flow simulation was performed on data obtained from a 73-year-old postoperative AVB patient. Three-dimensional cine phase-contrast magnetic resonance imaging at 3 Tesla was used to acquire flow data and to set up the simulation. The vascular geometry was reconstructed using computed tomography angiograms. Flow simulations were implemented at various ratios of the flow rate between the ascending aorta and the graft. Results were visualized by streamline and particle tracing.RESULTS: CFD demonstrated stagnation in the ascending aorta-arch when retrograde flow was dominant, indicating that the risk of thrombus formation exists in the ascending arch in cases with severe aortic stenosis and/or poor left ventricular function. Meanwhile, stagnation was observed in the proximal descending aorta when the antegrade and retrograde flow were equivalent, suggesting that the descending aorta is critical when aortic stenosis is not severe.CONCLUSIONS: Flow stagnation in the aorta which may cause thrombus was observed when retrograde flow was dominant and antegrade/retrograde flows were equivalent. Our results suggest that anticoagulants might be recommended even in patients who receive biological valves.