• Journal of Biomedical Engineering Research
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• v.19 no.2
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• pp.183-188
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• 1998

Von Mises stress and compliance distribution was evaluated using a finite element analysis on the end-to-side anastomosis of an artery with length of 20-24mm, inner diameter of 4mm, thickness of 0.5mm and a PTFE graft with length of 10mm, inner diameter of 2mm, thickness of 0.2mm when the anastomotic angle was taken from 30$^{\circ}$~90$^{\circ}$ in every 10$^{\circ}$ and the diameter ratio from 0.1-1 in every 0.1. The inner pressure of 1330 dyne/$\textrm{mm}^2$ was applied inside the 2 conduits. It was found that the compliance whose magnitude is larger on the acute angle anastomotic side than on the abtuse angle side became larger as the anastomotic angle became smaller and the diameter ratio larger and that the equivalent stress on the acute angle anastomotic side was larger than that on the abtuse angle side and became larger as the anastomotic angle and the diameter ratio became larger.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.05
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• pp.334-337
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• 1997

Von Mises stress and compliance distribution was evaluated using a finite element analysis on the end-to-side anastomosis of an artery with length of $20\sim24mm$, inner diameter of 4mm, thickness of 0.5mm and a PTFE graft with length of 10mm, inner diameter of 2mm, thickness of 0.2mm when the anastomotic angle was taken from $30^{\circ}\sim90^{\circ}$ in every $10^{\circ}$ and the diameter ratio from $0.1\sim1$ in every 0.1. The inner pressure of $1330dyne/mm^2$ was applied inside the 2 conduits. It was found that the compliance whose magnitude is larger on the acute angle anastomotic side than on the acute angle side became larger as the anastomotic angle became smaller and the diameter ratio larger and that the equivalent stress on the acute angle anastomotic side was larger than that on the abtuse angle side and became larger as the anastomotic angle and the diameter ratio became larger.

• Journal of Biomedical Engineering Research
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• v.18 no.3
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• pp.253-259
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• 1997

Von Mises stress and compliance distribution was evaluated using a finite element analysis on the anastomosis of an artery with length of 20mm(z direction, along the horizental artery), inner diameter of 4mm, thickness fo 0.5mm and a PTFE graft with length of 5.7mm, inner diameter of 2mm, thickness of 0.2mm when anastomotic angle was $45^{\circ}$ and inner pressure of 1330 dyne/mm2 was applied inside the 2 conduits. From the analysis results were obtained as follows. (1) Artery diameter increased in both horizontal x(along the length of artery) and vertical y(perpendicular to the length of artery)directions and the magnitude of that in x direction was bigger than that in y direction. (2) The compliance was maximum on the anastomosis, especially on that with acute angle. The reduction of compliance was observed from the anastomosis area to the either right or left end. (3) The equivalent stress was maximum on top in the y direction and minimum on the nodes apart $110^{\circ}$ in circumferential direction from the top. (4) The equivalent stress was maximum in t도 vicinity of anastomosis with acute angle along the longitudinal direction of the artery. This trend was also observed along the PTFE graft.

• Proceedings of the KOSOMBE Conference
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• v.1995 no.05
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• pp.104-108
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• 1995

Von Mises stress and compliance distribution was evaluated using a finite element analysis on the anastomosis of an artery with length of 20mm, inner diameter of 4mm, thickness of 0.5mm and a PTFE graft with length of 5.7mm, Inner diameter of 2mm. thickness of 0.2mm. When anastomotic angle was taken as $45^{\circ}$ and inner pressure of $1330\;dyne/mm^2$ was applied inside the 2 conduits. From the analysis results were obtained as follows. (1)Artery diameter increased in both horizontal x and vertical y directions and the magnitude of that in x direction was bigger than in y direction. (2) The compliance was maximum on the anastomosis. especially on that with acute angle. This reduced approaching to the right or left end. (3) The equivalent stress was maximum on top in the y direction and winimum on the nodes around $110^{\circ}$ in circumferential direction from the top. (4) The equivalent stress was maximum in the vicinity of anastomosis with acute angle along the longitudinal direction of the artery. This trend was also observed along the PTFE graft.

• Journal of Biomedical Engineering Research
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• v.20 no.5
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• pp.617-624
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• 1999

• Journal of Biomedical Engineering Research
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• v.13 no.4
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• pp.339-352
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• 1992

A numerical simulation of the steady and pulsatile flow across the end-to-side anastomosis was performed In order to understand the role of flow dynamics in the preferential bevel opment of distal anastomotic intimal hyperplasla. The finite element technique was employed to solve two-dimensional unsteady pulsatile flow in that region. The results of the steady flow revealed that low shear stresses occur at the proximally occluded host artery and at the recirculation region in the Inner wall just distal to the toe region of the anastomosis. The nor- mal;zed wall shear rate was increased, as was the recirculation zone size in the host artery of the by-pass graft anastomosis, with increased anastomotic junction angle. In order to min imize the size of the low wall shear region which might result in the intimal hyperplasia in the by-pass graft anastomosis, a smaller anastomotic junction angle is recommended. The pulsatile flow simulation revealed flow that regions of low and ascillating mali shear do exist near the anastomosis as In the steady simulation. The shift of stagnation point depends on the pulsation of the flow. As the flow was accelerated at systole, the stagnation point moved downstream, disappered at early diastole and reappeared during late diastole. Low shear stress was also found along both walls of the occluded proximal artery. However, the diastolic flow behavior is quite different from the steady results. The vortex near the occluded artery moved downstream and inwardly during late systole, and disappeared during diastole. Recirculations proximal to the toe and heel regions were significant during diastole. Shear stress oscillation was found along the opposite wall. The results of the present study revealed that tow shear occurs at the proximally occluded host artery aud the recirculation region in the inner wall Just dlstal to the toe region of the anastomosis. The present study suggested that the regions of fluctuated wall shear stress wit flow separation is correlated with the preferential developing regions of anastomosis neointial fibrous hyperplasia.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.203-206
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• 1996

To understand the local fluid dynamics for different desists of Fontan operation, five models were made out of Pyrex glass to facilitate in-vitro study. Model I, II and III have same position of the center of the anastomosis of the IVC( inferior vena cava) with that of the SVC(superior vena cava), but Model IV and V have 10 mm offset between them. Also the anastomotic junction angles are different(Model I and $IV:90^{\circ}$, Model II and $V:70^{\circ}$, Model $III:45^{\circ}$). These models were then connected to a flow loop for flow visualization study. In Model I any dominant vortex was not seen in the central region of the juntion, but a large unstable vortex was created in the Model II and III. In Model IV and V a significant stagnation region was created in the middle of the offset region. It also showed that the flow direction from the IVC and SVC to the LPA(left pulmonary artery) and RPA(right pulmonary artery) highly depends on the offset of the junction rather than the anastomotic junction angle.

• Journal of Biomedical Engineering Research
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• v.15 no.2
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• pp.143-150
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• 1994

Wall shear rate or stress is believed to be a major hemodynamic variable influencing atherosclerosis and artery-graft anastomic intimal hyperplasia. The purpose of this study is to verify the effects of radial wall motion, artery-graft compliance and diameter mismatch, and impedance phase angle on the wall shear rate distribution near an end-to-end artery-graft anastomosis model. The results show that radial wall motion of the elastic artery model lowers the mean wall shear rates under pulsatile flow condition by 15 to 20 % comparing to those under steady flow condition at the same mean flow rate. Impedance phase angle seems to have small effects on the mean and amplitude of the wall shear rate distribution. In order to study the effects of compliance and diameter mismatch on the wall shear rates, two models are studied-Model I has 6% and Model I has 6% and Model II has 11% smaller graft diameter. Divergent geometry caused by diameter mismatch near the distal sites reduces the mean wall shear rates significantly, and this low shear region is believed to be prone to intimal hyperplasia.

• International Journal of Vascular Biomedical Engineering
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• v.1 no.1
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• pp.41-47
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• 2003

The patency rates of small diameter vascular grafts are disappointing because of the formation of thrombus and intimal hyperplasia. Among the various factors influencing the success of graft surgery, the compliance and the size of a graft are believed to be the most important physical properties of a vascular graft. Mismatch of compliance and size between an artery and a graft alters anastomotic flow characteristics, which may affect the formation of intimal hyperplasia. Among the hemodynamic factors influencing the development of intimal hyperplasia, the wall shear stress is suspected as the most important one. The wall shear stress distributions are experimentally measured near the end-to-end anastomosis models in order to clarify the effects of compliance and diameter mismatch on the hemodynamics near the anastomosis. The effects of radial wall motion, diameter mismatch and impedance phase angle on the wall shear rate distributions near the anastomosis are considered. Compliance mismatch generates both different radial wall motion and instantaneous diameter mismatch between the arterial portion and the graft portion during a flow cycle. Mismatch in diameter seems to be affecting the wall shear rate distribution more significantly compared to radial wall motion. The impedance phase angle also affects the wall shear rate distribution.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.153-159
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• 2012

Bypass anastomosis is frequently adopted for surgical treatments of stenosed coronary arteries. Optimal coronary bypass grafting should be investigated to improve the patency in arterial bypass techniques. The objective of this study is to analyze the effects of Y-grafting bypasses and T-grafting bypasses for various bifurcation and anastomotic angles. In order to find the optimal geometric configuration, the hemodynamic characteristics are obtained and compared with each other for different geometries. We found that both the left anterior descending artery (LAD) and left circumflex artery (LCX) blood flows were distributed evenly when the bypass grafting angle and bifurcated angle were $30^{\circ}$ and $15^{\circ}$, respectively,.