## 4 Discussion
This study indicated that the higher OSI value was mainly detected at the LCX branch proportionate to the bifurcation angles. The blood flow from the LMCA to the bifurcation region and the structure of stent could cause an obvious disturbance in flow, and that could cause wall shear stress of an adjacent region's oscillations. Hence, the OSI value of lesion-caused capacity would be rapidly raised at the LCX branch. The result of the arterial branches revealed that the OSI of the LCX was maxed among three branches, and then when located at the LMCA, the LAD showed minimally in the arteries A and B. Both Culotte and Kissing techniques in the stenting structures around the bifurcation area were more complex than the T-stenting. Moreover, the usage of double stents in a deformed structure could interfere with the blood flow velocity and disturbance, resulting in the OSI increasing and a high risk of restenosis. Furthermore, according to the OSI distribution of the arterial branches, the high OSI was mainly concentrated at the regions C and D, which was located at the lateral side of the LCX arterial wall. Importantly, the distribution tendency of the OSI was consistent with the blood flow in the LCX branch. The CFD results of the low TAWSS and the OSI in the three branches of the two types of arteries indicated that the LCX branch near bifurcation was evidence of a high risk of stent stenosis. This outcome was the same as the clinical consequence of bifurcation-induced restenosis by using the double-stant technique. The previous literatures have pointed out that the stenosis rate at the LCX branch is approximately 12% [47; 48]. The distributions of the blood flow velocity and wall shear stress presented that the inflated truss structure of the in-stent disturbed the blood flow on the lateral side of the arterial wall and generated recirculatory flow, causing the local effect of the low blood flow velocity. The low TAWSS significantly affected lipid and platelet deposition. The outcome of this study was consistent with the experimental results of an in vitro bifurcation model by [PERSON] [49]. In terms of bifurcation angle effects, the results of the three bifurcation angles in this study indicated that the large bifurcation angle could cause recirculatory flow and increase the area of low wall shear stress. This finding is also consistent with an in vitro study in a research report by [PERSON] [50]. The stent expansion by balloon inflation could change the boundary layer separation on the lateral side of the arterial wall to generate recirculatory flows. In a clinical observation, the large bifurcation angle in the artery could lead to larger recirculatory flows. [PERSON] et al. [51] proposed that the stent length in the LCX branch would be affected by local hydrodynamics by using the double stent technique. The factor of a longer stent in the side branch may cause low wall stress and a high OSI, which will adversely affect the hemodynamics of the side branch. The T-stenting in this study had placed a complete stent on the LCX branch, but both of the Culotte and Kissing techniques had only a half stent structure on the LCX branch. Therefore, the distribution of the low TAWSS and high OSI in the T-stenting technique is indeed greater than both of the Culotte and Kissing techniques. This outcome is consistent with the previous research of [PERSON]'s study [51]. The result of this study indicated that the T-stenting technique was evidenced as the worst performance with the quantitative process of the TAWSS and the OSI. In other worlds, the restenosis probability of the T-stenting technique is higher than with the Culotte and Kissing techniques. Although the T-stenting is worse than the other two stenting techniques, each stenting technique has some problems of potential hemodynamic. For example, the Culotte technique in the LMCA branch performed a layer overlap of two metal stents, causing a blood disturbance in the overlapped region.