本研究主要是利用數值方法來模擬真實人體的左冠狀動脈(Left Coronary Artery,
LCA)中血液流動情況。所分析的左冠狀動脈血管是運用電腦斷層掃描(Computer
Tomography, CT) 所取得, 且來自於不同的病例資料,因此分歧的角度、血管的管
徑及幾何等情形皆不相同。針對健康的兩分歧(bifurcate)與三分歧(trifurcate)的
左冠狀動脈以有限體積法進行流場型態分析與血液對管壁造成表面應力之研究,
並比較其差異性。針對這些不同情形的左冠狀動脈, 本研究將觀察血液的流場型
態以及作用在管壁上的表面應力分布, 且對心血管病變情況進行預測。
由流場的結果可以發現, 在收縮與舒張加速時期, 其流場呈現平順的流動, 而
在舒張減速時期,流場變化較為劇烈。而由於分歧角度的影響,使得左前降支(Left
Anterior Descending, LAD) 或左旋支(Left Circumflex, LCX) 入口處外側會形成
不穩定的渦漩效應, 對管壁形成震盪剪應力與低剪應力之作用, 因此可能容易傷
害到血管的內膜,時間日積月累之後,可能有發生動脈粥樣硬化症的危險。除了分
歧角度造成流場變化之外, 彎管狀血管的最彎處在心臟舒張減速時, 會形成彎管
流(Dean flow) 或渦漩效應的現象,此情況亦會增加動脈粥樣硬化症的機會。從流
量上可以發現, 血液流量會受到管徑及分歧角度所影響, 血管管徑愈大血液流量
也愈大, 而分歧的角度愈大所流入的流量也就愈多。與兩分歧左冠狀動脈的比較,
三分歧左冠狀動脈多了左中央支(Left Ramus Intermediate, LRI) 的存在, 在壓力
分布上, 提高分歧區中央高壓的範圍, 增加壓力的損失及剪應力的震盪性,更提高
了渦漩效應發生的臨界角度, 因此左中央支(LRI) 對於左冠狀動脈流場有很大的
影響力。

The aim of this study is to investigate variations of blood flows in vitro Left Coronary Arteries(LCA) using numerical approaches. The geometry of LCA comes from Computer Tomography(CT) measurements of 5 patients, so the angles of
trifurcation, diameter, curvature of blood vessels are different. Subsequently, we analyze flow patterns and stress distributions in bifurcate and trifurcate LCA using a finite volume model. We are consider blood flows in LCA with various geometric parameters, observe flow patterns and surface stress distributions on the artery walls, and predict possibility of cardiovascular diseases. In terms of the obtained numerical results, the blood flows smoothly in acceleration of systole and diastole, but flow patterns change seriously in deceleration of diastole. Due to the influence of angles of bifurcation, there are vortices close to the outside walls at Left Anterior Descending(LAD) or Left Circumflex(LCX) entrance. The oscillatory and low shear stress caused by a vortical flow affects the vessel walls. Hence the vessel intima may be injured by variation of stress. As a result, it will become atherosclerotic for a long term in LCA. In addition to the influence of angle, a Dean flow is observed in the curved part of LCA in deceleration of diastole. It may cause astherosclerosis under this condition. The mass flow rate of blood is proportional to diameter and angle of bifurcation. LRI
not only increases pressure loss and oscillatory shear stress in trifurcate area, but also raises the critical angle with vortical effect. Therefore flow patterns of LCA are influenced obviously by LRI.

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