Influence of Bifurcation Angle on In-Stent Restenosis at the Vertebral Artery Origin: A Simulation Study of Hemodynamics

Endovascular surgery has become one of the main methods for treatment of intracranial arterial stenosis. Its safety and efficacy has been greatly improved. However, in-stent restenosis (ISR) remains a major problem challenging interventional treatment. In this paper, the formation of ISR at the proximal end of stent was concerned from the aspects of the effect of bifurcation angle. Five realistic models with different bifurcation angle (44.49A degrees, 74.72A degrees, 80.53A degrees, 86.10A degrees and 95.37A degrees) were built by using Mimics. Computational fluid dynamics was used to analyze the influence of vertebral artery bifurcation angle on the ISR. The area of low wall shear stress (WSS, < 1.5 Pa) at the proximal end of vertebral artery extracted at the systole in the five models were 1.05, 1.08, 3.90, 2.98 and 1.05e-4 m(2) respectively. The area of low WSS extracted at the diastole were 2.17, 3.26, 2.43, 2.66 and 2.89e-4 m(2) respectively. Moreover, the time-averaged WSS of the five models were 4.19, 3.78, 5.01, 3.78 and 4.15 Pa respectively. Overall, with the increase of bifurcation angle, the area of lesion is prone to increase: the contact of blood particles with the luminal surface will be prolonged. The area of low WSS in the model with the bifurcation angle of 74.72A degrees is particularly high and this model is perhaps the most prone to restenosis.