scholarly journals Impact of Competitive Flow on Hemodynamics in Coronary Surgery: Numerical Study of ITA-LAD Model

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Jinli Ding ◽  
Youjun Liu ◽  
Feng Wang ◽  
Fan Bai
Keyword(s):  
Shear Stress ◽  
Coronary Artery ◽  
Wall Shear Stress ◽  
Numerical Study ◽  
Artery Bypass ◽  
Bypass Graft ◽  
Coronary Bypass ◽  
Coronary Artery Bypass Grafts ◽  
Wall Shear ◽  
The Impact

Competitive flow from native coronary artery is considered as a major factor in the failure of the coronary artery bypass grafts. However, the physiological effects are not very clear. The aim is to research the impact of competitive flow caused by different left anterior descending (LAD) artery stenosis degrees on hemodynamics in internal thoracic artery (ITA) bypass graft. An idealized ITA-LAD model was built in CAD tools. The degree of the competitive flow was divided into five classes according to different LAD stenosis degrees: higher (no stenosis), secondary (30% stenosis), reduced (50% stenosis), lower (75% stenosis) and no competitive flow (fully stenosis). Finite volume method was employed for the numerical simulation. The flow velocity distributions, wall shear stress and oscillatory shear index were analyzed. Results showed that higher competitive flow in the bypass graft would produce unbeneficial wall shear stress distribution associating with endothelial dysfunction and subsequent graft failure. The coronary bypass graft surgery was preferred to be carried out when the LAD stenosis was higher than 75%.

Preliminary Near Wall Hemodynamic Evaluation of a Coronary Artery Bypass Graft Model With a Flow Streamlining Implant

2002 ◽  
Author(s):  
Pedro D. Pedroso ◽  
Andreas S. Anayiotos ◽  
Brad L. Hershey ◽  
Evangelos Eleftheriou ◽  
William L. Holman
Keyword(s):  
Shear Stress ◽  
Coronary Artery ◽  
Wall Shear Stress ◽  
Coronary Artery Bypass Graft ◽  
Coronary Artery Bypass ◽  
Saphenous Vein ◽  
Artery Bypass ◽  
Bypass Graft ◽  
Artery Bypass Graft ◽  
Wall Shear

Coronary artery disease (CAD) is the leading cause of death in the world today. According to the American Heart Association 529,659 people in 1999 died as a result of CAD [1]. Starting in the 1960’s, surgeons have used Coronary Artery Bypass Graft (CABG) techniques in order to reestablish blood flow to the heart. Today, the procedure remains the same, using autologous grafts, such as the mammary artery and the saphenous vein. An unresolved problem, is that a significant number of CABGs reocclude months to years postoperatively. In the case of Saphenous Vein Grafts (SVGs) typically 50% of these bypasses are totally occluded months to years after the procedure, the remaining half being more than 50% occluded [2]. The re-occlusion of CABGs is due to a process labeled intimal hyperplasia (IH). Investigators have shown that IH, believed by some to be a remodeling process, occurs at branch sites, regions of curvature, and anastomotic junctions [3,4]. At these sites there are low residence times, slow secondary structures, disturbed flow, and areas of recirculation, therefore the onset of IH is believed to be hemodynamically linked. Most recently, floor IH has been attributed to four variables: time averaged wall shear stress (WSS), oscillating shear index (OSI), spatial wall shear stress gradients (WSSG), and temporal WSSG [5]. Adverse values of these parameters, in the case of SVGs, are believed to be caused by impedance mismatch at the anastomosis site. Over time this characteristic causes a bulge at the sinus. Such a morphology additionally contributes to disturbed flows which tend to propagate down the CABG and are believed to play a major role in the development of IH and the eventual failure of the graft.

scholarly journals Flow and wall shear stress in end-to-side and side-to-side anastomosis of venous coronary artery bypass grafts

2007 ◽  
Vol 6 (1) ◽  
pp. 35 ◽  
Author(s):  
Thomas Frauenfelder ◽  
Evangelos Boutsianis ◽  
Thomas Schertler ◽  
Lars Husmann ◽  
Sebastian Leschka ◽  
...  
Keyword(s):  
Shear Stress ◽  
Coronary Artery ◽  
Wall Shear Stress ◽  
Coronary Artery Bypass ◽  
Artery Bypass ◽  
Coronary Artery Bypass Grafts ◽  
Bypass Grafts ◽  
Wall Shear

Characterizing Flow in the Vertebro-Basilar System Using MR in Conjunction With Subject-Specific Computational Models

2010 ◽  
Author(s):  
Amanda K. Wake ◽  
John C. Gore ◽  
J. Christopher Gatenby
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Vascular Graft ◽  
Graft Failure ◽  
Computational Models ◽  
Artery Bypass ◽  
Bypass Graft ◽  
Arterial Graft ◽  
Vessel Patency ◽  
Wall Shear

Coronary artery bypass graft failure is often a consequence of intimal hyperplasia (IH), which correlates with hemodynamic factors (e.g., wall shear stress); this relationship has been used to evaluate arterial graft design [e.g., 1–4]. The vertebro-basilar system is a native arterial merge (i.e., two arteries, the vertebrals, converge into a single artery, the basilar artery); thus, characterizing the flow field of this system in healthy subjects could be useful for early detection of anomalies (e.g., aneurysms) or for vascular graft design improvements to ensure graft/vessel patency. This study uses high field MR and phase contrast MR (PCMR) to investigate the hemodynamics of the vertebro-basilar system in a healthy, adult subject for predicting pathophysiologically-relevant flow patterns (e.g., low wall shear stress) that are related to IH and subsequent graft failure.

Coronary Artery Stenting Affects Wall Shear Stress Topological Skeleton

2022 ◽  
Author(s):  
Claudio Chiastra ◽  
Valentina Mazzi ◽  
Maurizio Lodi Rizzini ◽  
Karol Calò ◽  
Anna Corti ◽  
...  
Keyword(s):  
Shear Stress ◽  
Coronary Artery ◽  
Wall Shear Stress ◽  
Vascular Diseases ◽  
Human Coronary Artery ◽  
Term Outcome ◽  
Clinical Images ◽  
Long Term Outcome ◽  
Wall Shear ◽  
The Impact

Abstract Despite the important advancements in the stent technology for the treatment of diseased coronary arteries, major complications still affect the post-operative long-term outcome. The stent-induced flow disturbances, and especially the altered wall shear stress (WSS) profile at the strut level, play an important role in the pathophysiological mechanisms leading to stent thrombosis (ST) and in-stent restenosis (ISR). In this context, the analysis of the WSS topological skeleton is gaining more and more interest by extending the current understanding of the association between local hemodynamics and vascular diseases. The present study aims to analyze the impact that a deployed coronary stent has on the WSS topological skeleton. Computational fluid dynamics simulations were performed in three stented human coronary artery geometries reconstructed from clinical images. The selected cases presented stents with different designs (i.e., two contemporary drug eluting stents and one bioresorbable scaffold) and included regions with stent malapposition or overlapping. A recently proposed Eulerian-based approach was applied to analyze the WSS topological skeleton features. The results highlighted that the presence of single or multiple stents within a coronary artery markedly impacts the WSS topological skeleton. In particular, repetitive patterns of WSS divergence were observed at the luminal surface, highlighting a WSS contraction action proximal to the struts and a WSS expansion action distal to the struts. This WSS action pattern was independent from the stent design. In conclusions, these findings could contribute to a deeper understanding of the hemodynamic-driven processes underlying ST and ISR.

A Computational Technique for Robust Optimization of Cardiovascular Bypass Graft Surgeries

2010 ◽  
Author(s):  
Sethuraman Sankaran ◽  
Alison L. Marsden
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Operative Mortality ◽  
Artery Bypass ◽  
Bypass Graft ◽  
Computational Technique ◽  
First Year ◽  
Synthetic Material ◽  
Plaque Deposition ◽  
Wall Shear

Bypass graft (BG) surgeries involve surgical construction of a graft over a blocked blood vessel. The graft can either be native tissue of the patient or a synthetic material. Some commonly performed BG surgeries include aorto-bifemoral, femoro-popliteal, femoro-tibial, and coronary artery bypass (CABG). The operative mortality rate for CABG is around 3%. Around 15 to 30% of bypass grafts occlude within the first year of surgery, increasing to over 50% after 10 years. Graft incompatibility, and hemodynamic factors such as blood recirculation, low wall shear stress, and abnormal wall shear stress gradients play an important role in the onset and development of intimal thickening and plaque deposition (atherogenesis).

Pressure Induced Strain at Femoral Artery Bypass Graft Junctions

2007 ◽  
Author(s):  
Triona Campbell ◽  
Reena Cole ◽  
Michael O’Donnell
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Artery Bypass ◽  
Bypass Graft ◽  
Arterial Disease ◽  
Shear Stresses ◽  
Artery Bypass Graft ◽  
Short Period ◽  
Wall Shear ◽  
Hydrodynamic Stresses

Femoral or femoropopliteal artery bypass graft junctions have a predilection for failure due to restenosis. It has been clinically proven that vascular reconstructions tend to restenose within a short period of time [1]. Extensive studies have cited wall shear stresses as being primarily responsible and definite correlations between hydrodynamic stresses in the arterial wall and arterial disease have been shown [2,3]. However intensive investigations into wall shear stresses have lead to conflicting arguments on the proliferation and propagation of stenoses. It was concluded by Freidman [4] that the intima at sites exposed to relatively high or unidirectional shears thickened initially, but as time progressed the greatest thicknesses were ultimately achieved at sites exposed to lower or more oscillatory shear environments. A contradicting view was expressed by Nazemi [5] that low wall shear stress contributed to the onset of atherosclerotic plaque formation, whilst high wall shear stress encouraging plaque growth. A number of studies have however established a statistically significant correlation between pressure and intimal hyperplasia and concluded that blood pressure and not blood flow is the primary factor responsible for the localization of atherosclerosis [6–8].

P3588The synergistic effect of NIRS-detected lipid-rich plaque and 5 different multidirectional wall shear stress metrics on human coronary plaque growth

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
E M J Hartman ◽  
A M Kok ◽  
A Hoogendoorn ◽  
F J H Gijsen ◽  
A F W Steen ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Synergistic Effect ◽  
Coronary Arteries ◽  
Wall Thickness ◽  
Plaque Progression ◽  
Lipid Rich Plaque ◽  
Plaque Growth ◽  
Wall Shear ◽  
The Impact

Abstract Introduction Local wall shear stress (WSS) metrics, high local lipid levels (as detected by near-infrared spectroscopy (NIRS)), as well as systemic lipid levels, have been individually associated with atherosclerotic disease progression. However, a possible synergistic effect remains to be elucidated. This study is the first study to combine WSS metrics with NIRS-detected local lipid content to investigate a potential synergistic effect on plaque progression in human coronary arteries. Methods The IMPACT study is a prospective, single centre study investigating the relation between atherosclerotic plaque progression and WSS in human coronary arteries. Patients with ACS treated with PCI were included. At baseline and after 1-year follow-up, patients underwent near-infrared spectroscopy intravascular ultrasound (NIRS-IVUS) imaging and intravascular doppler flow measurements of at least one non-culprit coronary artery. After one month, a CT angiography was made. CT derived centreline combined with IVUS lumen contours resulted in a 3D reconstruction of the vessel. The following WSS metrics were computed using computational fluid dynamics applying the vessel specific invasive flow measurements: time-average wall shear stress (TAWSS), relative residence time (RRT), cross-flow index, oscillatory shear index and transverse wall shear stress. Low TAWSS is known as pro atherogenic, in contrast to all the other shear stress metrics, at which a high magnitude is pro-atherogenic. The arteries were divided into 1.5mm/45° sectors. Based on NIRS-IVUS, wall thickness change over time was determined and NIRS positive sectors detected. Furthermore, per vessel the shear stress was divided into tertiles (low, intermediate, high). To investigate the synergistic effect of local lipids on shear stress related plaque growth, wall thickness change over time was related to the different shear stress metrics comparing the NIRS-positive with the NIRS-negative sectors. Results 15 non-culprit coronary arteries from the first 14 patients were analyzed (age 62±10 years old and 92.9% male). A total of 2219 sectors were studied (5.2%, N=130, NIRS-positive) for wall thickness changes. After studying all five shear stress metrics, we found for TAWSS and RRT that presence of lipids, as detected by NIRS, amplified the effect of shear stress on plaque progression (see figure). Sectors presenting with lipid-rich plaque, compared to NIRS-negative sectors, showed more progression when they were exposed to low TAWSS (p=0.07) or high RRT (p=0.012) and more regression in sectors exposed to high TAWSS (p=0.10) or low RRT (p=0.06). Delta wall thickness vs shear stress Conclusion We presented the first preliminary results of the IMPACT study, showing the synergistic effect of lipid rich plaque and shear stress on plaque progression. Therefore, intravascular lipid-rich plaque (NIRS) assessment has added value to shear stress profiling for the prediction of plaque growth, leading to improved risk stratification. Acknowledgement/Funding ERC starting grant 310457

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