A numerical study on steady flow in helically sinuous vascular prostheses

Lee, Kyung Eun; Lee, Jeong S.; Yoo, Jung Yul

doi:10.1016/j.medengphy.2010.09.005

Cited by 17 publications

(14 citation statements)

References 20 publications

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“…1 However, for Re between 500 and 6300, the ratio was approximately 0.328(d/D eq ) 0.15 Re 1/3 . Visualization studies demonstrated that the secondary rotation was transformed from a two counter-rotating vortices structure to a one-recirculation one with the increase in the torsion of the tube, which was consist with the aforementioned studies of grafts by Lee et al 52,99 In addition, the fact that helical tubes enhanced heat transport would imply that helical grafts intensified oxygen transport. 75 Re-stenosis of the End-to-Side Anastomosis…”

Section: Occlusion Of Arterial Bypass Grafts and Arteriovenous Shuntssupporting

confidence: 68%

“…7 After the invention of Swirl Graft, several researchers numerically investigated the hemodynamics in the Swirl Graft and optimized the design of grafts like Swirl Graft to improve the hemodynamic performance. Lee et al 52 found that the torsion of the helical grafts would remarkably change the Dean vortices produced by the curvature to a predominantly single vortex. Under the same strength, helical flow with a predominantly single vortex would be better than that with two symmetrically paired and counter-rotating vortices, since the latter structure has relatively low shear regions associated with stagnation points.…”

Section: Occlusion Of Arterial Bypass Grafts and Arteriovenous Shuntsmentioning

confidence: 99%

“…Under the same strength, helical flow with a predominantly single vortex would be better than that with two symmetrically paired and counter-rotating vortices, since the latter structure has relatively low shear regions associated with stagnation points. 52,57,101 In addition, when compared to the blood flow without helical flow, helical flow with two vortices would still enhance the flow transport. Lee et al shown that relatively low wall shear stress in the helical tube with two vortices did not differ significantly from that in the straight tube without helical flow.…”

Section: Occlusion Of Arterial Bypass Grafts and Arteriovenous Shuntsmentioning

confidence: 99%

“…However, the level of high wall shear stress was much higher than that in the straight tube. 52 Zheng et al 109 numerically simulated the steady flows in both helical and conventional grafts. It was showed that when compared with conventional grafts, the helical ones resulted in helical flow and led to more uniformly distributed flow field and high wall shear stress but also a higher pressure drop.…”

Section: Occlusion Of Arterial Bypass Grafts and Arteriovenous Shuntsmentioning

confidence: 99%

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Physiological Significance of Helical Flow in the Arterial System and its Potential Clinical Applications

et al. 2014

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Helical flow in the human aorta is possibly a typical example of 'form follows function' in the vascular system. The helical blood flow may provide guaranties for the inner surface of the ascending aortic wall to get smooth and even washing by the blood so that atherosclerotic plaques can hardly form in the area of the ascending aorta. It has been documented that the phenomenon of helical flow of blood is not just localized in the ascending aorta, it also exists in several large arteries and veins as well. Preliminary studies demonstrated the widely existing helical flow might play positive physiological roles in facilitating blood flow transport, suppressing disturbed blood flow, preventing the accumulation of atherogenic low density lipoproteins on the luminal surfaces of arteries, enhancing oxygen transport from the blood to the arterial wall and reducing the adhesion of blood cells on the arterial surface. These roles of helical blood flow may lessen the burden of arteries and protect the arteries from the pathology of atherosclerosis, thrombosis, and intimal hyperplasia. The great development of time-resolved three-dimensional phase contrast MRI (flow-sensitive 4D-MRI) and the advent of dimensionless indices such as helical flow index proposed to characterize helical flow make clinic quantification of the helical flow in the human large arteries possible. Moreover, researchers probed into the possibility to apply the mechanism of helical flow to the design of vascular interventions to reduce thrombus formation and intimal hyperplasia caused by abnormal flow conditions.

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Section: Occlusion Of Arterial Bypass Grafts and Arteriovenous Shuntssupporting

confidence: 68%

Section: Occlusion Of Arterial Bypass Grafts and Arteriovenous Shuntsmentioning

confidence: 99%

Section: Occlusion Of Arterial Bypass Grafts and Arteriovenous Shuntsmentioning

confidence: 99%

Section: Occlusion Of Arterial Bypass Grafts and Arteriovenous Shuntsmentioning

confidence: 99%

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Physiological Significance of Helical Flow in the Arterial System and its Potential Clinical Applications

et al. 2014

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“…Dean flow is commonly observed in curved piping. In the absence of Dean flow, the presence of helical flow and higher helicity values are associated with improved WSS magnitudes and distribution due to centrifugal forces [21,29].…”

Section: Simulation Setupmentioning

confidence: 99%

Computational Fluid Dynamics Evaluation of the Cross-Limb Stent Graft Configuration for Endovascular Aneurysm Repair

Shek

Tse

Nabovati³

et al. 2012

Journal of Biomechanical Engineering

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The technique of crossing the limbs of bifurcated modular stent grafts for endovascular aneurysm repair (EVAR) is often employed in the face of splayed aortic bifurcations to facilitate cannulation and prevent device kinking. However, little has been reported about the implications of cross-limb EVAR, especially in comparison to conventional EVAR. Previous computational fluid dynamics studies of conventional EVAR grafts have mostly utilized simplified planar stent graft geometries. We herein examined the differences between conventional and cross-limb EVAR by comparing their hemodynamic flow fields (i.e., in the "direct" and "cross" configurations, respectively). We also added a "planar" configuration, which is commonly found in the literature, to identify how well this configuration compares to out-of-plane stent graft configurations from a hemodynamic perspective. A representative patient's cross-limb stent graft geometry was segmented using computed tomography imaging in Mimics software. The cross-limb graft geometry was used to build its direct and planar counterparts in SolidWorks. Physiologic velocity and mass flow boundary conditions and blood properties were implemented for steady-state and pulsatile transient simulations in ANSYS CFX. Displacement forces, wall shear stress (WSS), and oscillatory shear index (OSI) were all comparable between the direct and cross configurations, whereas the planar geometry yielded very different predictions of hemodynamics compared to the out-of-plane stent graft configurations, particularly for displacement forces. This single-patient study suggests that the short-term hemodynamics involved in crossing the limbs is as safe as conventional EVAR. Higher helicity and improved WSS distribution of the cross-limb configuration suggest improved flow-related thrombosis resistance in the short term. However, there may be long-term fatigue implications to stent graft use in the cross configuration when compared to the direct configuration.

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