Hemodynamic Analysis on the Anastomosis Angle in Arteriovenous Graft Using Multiphase Blood Model

Numerical analysis was performed for the effect of the venous anastomosis angle in a forearm arteriovenous graft for hemodialysis using a multiphase blood model. The geometry of the blood vessel was generated based on the patient-computed tomography data. The anastomosis angles were set at 15°, 30°, and 45°. The hematocrit was set at 34%, 45%, and 58%. The larger anastomosis angle, high wall shear stress area >11 Pa, increases to the side of the vein wall away from the anastomosis site. Further, the relatively low wall shear stress area, <3 Pa, occurs near the anastomosis site in larger anastomosis angles. Therefore, the effect of high wall shear stress has advantages in the vicinity of the anastomosis, as the anastomosis angle is larger, but disadvantages as the distance from the anastomosis increases. Moreover, patients with low hematocrit are advantageous for WSS area.

Potential relationship between high wall shear stress and plaque rupture causing acute coronary syndrome

Purpose: To investigate the detailed relationship between high wall shear stress (WSS) and plaque rupture (PR) in longitudinal and circumferential locations.Methods: Overall, 100 acute coronary syndrome (ACS) patients whose culprit lesions had PR documented by optical coherence tomography (OCT) were enrolled. Lesion-specific three-dimensional coronary artery models were created using OCT data. At the ruptured portion, tracing of the luminal edge of the residual fibrous cap was smoothly extrapolated to reconstruct the luminal contour before PR. Then, WSS was computed from computational fluid dynamics analysis. PR was classified into central-PR and lateral-PR according to the disrupted fibrous cap location.Results: In the longitudinal 3-mm segmental analysis, multivariate analysis demonstrated that higher WSS in the upstream segment was independently associated with Upstream-PR and a thinner fibrous cap was independently associated with Downstream-PR. In PR cross-sections, PR region had a significantly higher average WSS than the non-PR region. In the cross-sectional analysis, peak WSS was most frequently observed in the lateral region (66.7%) in lateral-PR, whereas that in central-PR was most frequently observed in the central region (70%). Multivariate analysis demonstrated that the presence of peak WSS at the lateral region, thinner broken fibrous cap, and larger lumen area were independently associated with lateral-PR, while the presence of peak WSS at the central region and thicker broken fibrous cap were independently associated with central-PR.Conclusions: A combined approach with computational fluid dynamics simulation and morphological plaque evaluation by OCT might help predict future PR-induced ACS events.

The quantitative comparison between high wall shear stress and high strain in the formation of paraclinoid aneurysms

In the hemodynamic study, computational fluid dynamics (CFD) analysis has shown that high wall shear stress (WSS) is an important parameter in cerebral aneurysm formation. However, CFD analysis is not more realistic than fluid–structure interaction (FSI) analysis given its lack of considering the involvement of vascular structures. To investigate the relationship between the hemodynamic parameters and the aneurysm formation, the locations of high WSS and high strain were extracted from the CFD and FSI analyses, respectively. Then the distances between the aneurysm formation site and the locations of high WSS or high strain were calculated. A total of 37 intracranial paraclinoid aneurysms were enrolled for quantitative comparison. Additionally, the dura mater was modeled to facilitate realistic results in FSI analysis. The average distance from the location of the aneurysm formation site to the high strain (1.74 mm $$\pm $$ ± 1.04 mm) was smaller than the average distance to the high WSS (3.33 mm $$\pm $$ ± 1.18 mm). The presence of dura mater also influenced the findings in the aneurysm formation site. High strain extracted by FSI analysis is an important hemodynamic factor related to the formation of cerebral aneurysms. Strain parameter could help to predict the formation of aneurysms and elucidate the appropriate treatment.