• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.707-708
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• 2002

Catheters are used to measure translesional pressure gradients in the stenosed coronary arteries. Catheter insertions during coronary angioplasty cause flow obstructions. A narrowed flow cross section with catheter present effectively introduced a tighter stenosis than the enlarged residual stenoses after balloon angiplasty. In general, the form of stenoses are no uniform. Sometimes, these are occurred the irregularly eccentricity If the analyses are conducted for uniform stenosed artery, the results will be underestimated. Thus, in this study, three dimensional computer simulations are conducted to investigate the flow blockage effects due to the catheter insertion during the coronary angioplasty. The results for the eccentric stenosed artery are compared with those of the concentric stenosed artery.

• Journal of Mechanical Science and Technology
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• 제19권6호
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• pp.1313-1320
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• 2005

Stenosed coronary artery may play an important role in various coronary heart diseases. However, it has not been known how much stenosed coronary artery affects coronary circulation system, quantitatively. The present study developed a mathematical model for microcirculation in the left common coronary artery (LCCA) with adopting a previously measured morphological data and mechanical properties of the coronary vessels. We examine the effect of percent diameter stenosis on blood flow rate and shear stress for two cases. Case I comprised of one-stenosed element at $10^{th}$ order ($\%$ diameter stenosis are 10, 30, and 50, respectively). Case II consisted of completely occluded element at $10^{th}$ order (number of occluded elements are 0, 1, and 2 out of 8, respectively). As the level of stenosis becomes severe, the shear stress increases significantly but the flow rate reduction was relatively small. However, for the occluded case, there was linearly proportional reduction of flow rate according to number of occluded elements. Either such high shear stress associated with coronary artery stenosis or reduced flow rate due to occlusion may cause atherosclerosis and myocardial ischemia.

• 대한의용생체공학회:의공학회지
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• 제20권5호
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• pp.617-624
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• 1999

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1919-1922
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• 2003

Bypass anastomosis are frequently adopted for surgical treatments. After the bypass grafting, the bypass artery is often occluded due to restenosis and/or anastomotic neointimal fibrous hyperplasia phenomena. Optimal coronary bypass anastomosis should be investigated to improve the patency for the arterial bypass techniques. The objective of this study is to investigate the influence of bypass with sequential bypass effects in the stenosed coronary artery. Numerical analyses are focused on the understanding of the flow patterns for different sequential anastomosis techniques. Blood flow field is treated as two-dimensional incompressible laminar flow. The finite volume method is adopted for discretization of the governing equations. The Carreau model is employed as the constitutive equation for blood. To find the optimal sequential bypass anastomotic configurations, the mass flow rates at the outlet of different models are compared quantitatively.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.717-720
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• 2002

The present study is to evaluate the performances of flow velocity and wall shear stress in the stenosed coronary artery using human in vivo hemodynamic Parameters and computer simulation. Initial and follow-up coronary angiographics in the patients with angulated coronary stenosis are performed. Follow-up coronary angiogram demonstrated significant difference in the percent of diameter in the stenosed coronary between two groups ($Group\;1:\;40.3{\%},\;Group\;2:\;25.5{\%}$). Flow-velocity wave obtained from in vivo intracoronary Doppler ultrasound data is used for the boundary condition for the computer simulation. Spatial and temporal variations of flow velocity vector and recirculation area are drawn throughout the selected segment of coronary models. The WSS of pre- and post-intracoronary stenting are calculated from three-dimensional computer simulation. Then negative shear stresses area on 3D simulation we noted on the inner wall of the post-stenotic area before stenting. The negative WSS is disappeared after stenting. High spatial and temporal WSS before stenting fell into within physiologic WSS after stenting. This finding was prominent in Model 2. The present study suggest that hemodynamic forces exerted by pulsatile coronary circulation termed WSS might affect on the evolution of atherosclerosis within the angulated vascular curvature. The local recirculation area which has low or negative WSS, might lead to progression of atherosclerosis.

• 대한기계학회논문집B
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• 제36권2호
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• pp.153-159
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• 2012

협착이 발생된 관상동맥의 치료를 위해 외과적인 수술방법으로는 이식우회로술이 많이 사용된다. 이식우회로술 시술 시 개존율 향상을 위해서는 최적의 혈관 문합 시술에 대한 연구가 필요하다. 본 연구의 목적은 Y-grafting bypass 와 T-grafting bypass 시술의 효과와 분지각도 및 문합각도 변화에 따른 문합효과를 분석하였다. 이를 위해 기하학적 형상을 최적화하고 각각의 기하학적 형상에 대해 혈류역학적 특성을 비교분석하였다. 이식혈관의 분지각도와 문합각도가 각각 $30^{\circ}$와 $15^{\circ}$일 경우에 LAD 와 LCX 쪽 모두 혈류량이 고르게 분배됨을 확인하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 추계 학술대회논문집
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• pp.152-157
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• 1999

For the simulation of the blood flow in coronary artery, the system modeling of coronary hemodynamics is combined with CFD technique. The blood flow in coronary artery interacts with the global coronary circulation. Especially in case of the coronary artery with stenosis, the interaction plays an important role in the hemodynamics of the circulation. In this study we present a combined numerical approach using both the CFD technique for flow simulation and the global system model of coronary circulation. We use a lumped parameter model for the global simulation of coronary circulation whereas the finite element method is employed to compute the viscous flow field in stenosed coronary artery, The time variation of the pressure drop due to stenosis is obtained from the proposed numerical method. Numerical results shows that the flow resistance and pressure drop due to stenosis has a relatively large value in systole.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 춘계학술대회
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• pp.111-115
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• 1997

The objective of present study is to obtain information about stenosis effects on the blood flow in the coronary artery bifurcation. The three dimensional steady of blood in the coronary artery bifurcation with stenosis and without stenosis are simulated using the finite volume method. Apparent viscosity of blood is represented as a function of shear rate by the Carreau models. Velocities vectors and wall shear stresses along the branch tubes with stenosis are compared with those of without stenosis for steady flows. Flow phenomena in the stenosed branch tubes are discussed extensively.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.585-590
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• 2001

The hemodynamic characteristics were compared using commercial CFD code for the stenosed coronary and abdominal arteries. Numerical calculations were carried out in the axisymmetric arteries over the stenotic diameter ratios ranging from 0.25 to 0.875 (6 cases) employing the typical physiological flow conditions. In case of the coronary artery, there was only one recirculation zone observed distal to the stenosis throat during the major portion of the period. However, in case of the abdominal aorta, there were complex recirculation regions found proximal and distal to stenosis throat. For both models, the wall shear stresses(WSS) increased sharply in the converging stenosis, reaching a peak just upstream of the throat, and became negative or low values in the post-stenotic recirculation region. As the results, the oscillatory shear index(OSI) was abruptly increased at the stenosis throat. For the coronary stenosis model, the second peak in the OSI was observed distal to the stenosis. The distance between the first peak and the second peak was increased as the degree of the stenosis was raised. On the orther hand, the abdominal stenosis model showed a complex oscillatory behavior in the OSI index and did not showed such a strong second peak. As the degree of stenosis was increased, recirculation regions of the both arteries were extended much longer and flow pattern became more complex.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 추계학술대회
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• pp.254-257
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• 1996

An aorto-coronary bypass graft is frequently adopted for the interventional therapy of the diseased atherosclerotic coronary artery grafting. The bypass artery is often occluded due to restenosis and/or anastomotic neointimal fibrous hyperplasia after bypass graft. The optimal aorto-coronary bypass procedure must be studied in order to improve patency rate for the arterial bypass techniques. The objective of this study is to investigate the influences of geometric dimensions of bypass on the hemodynamics around the anastomosis in the stenosed coronary artery with aorto-coronary bypass.