Interplay of Proximal Flow Confluence and Distal Flow Divergence in Patient-Specific Vertebrobasilar System

Xiaoping Yin,Yunlong Huo,Huaijun Liu,Xu Huang,Yundi Feng,Wenchang Tan,Josué Sznitman

doi:10.1371/journal.pone.0159836

Abstract

Approximately one-quarter of ischemic strokes involve the vertebrobasilar arterial system that includes the upstream flow confluence and downstream flow divergence. A patient-specific hemodynamic analysis is needed to understand the posterior circulation. The objective of this study is to determine the distribution of hemodynamic parameters in the vertebrobasilar system, based on computer tomography angiography images. Here, the interplay of upstream flow confluence and downstream flow divergence was hypothesized to be a determinant factor for the hemodynamic distribution in the vertebrobasilar system. A computational fluid dynamics model was used to compute the flow fields in patient-specific vertebrobasilar models (n = 6). The inlet and outlet boundary conditions were the aortic pressure waveform and flow resistances, respectively. A 50% reduction of total outlet area was found to induce a ten-fold increase in surface area ratio of low time-averaged wall shear stress (i.e., TAWSS ≤ 4 dynes/cm2). This study enhances our understanding of the posterior circulation associated with the incidence of atherosclerotic plaques.

Highlights

80% of strokes are attributed to the ischemic origin, of which 20% to 25% are located in posterior circulation [1]
We focused on the intracranial vertebrobasilar system that is comprised of vertebral arteries (VA) (LVA and RVA), basilar artery (BA), anterior inferior cerebellar artery (AICA), superior cerebellar arteries (SCA) (LSCA and RSCA) and posterior cerebral arteries (PCA) (LPCA and RPCA)
The present study focused on the interplay of upstream flow confluence (LVA and RVA merging into BA) and downstream flow divergence (BA bifurcating into SCAs and PCAs) in the vertebrobasilar system

Summary

Introduction

80% of strokes are attributed to the ischemic origin, of which 20% to 25% are located in posterior circulation [1]. The posterior circulation is generally supplied by the vertebrobasilar arterial system comprised of left and right vertebral arteries (VA), anterior inferior cerebellar artery (AICA), basilar artery (BA), left and right superior cerebellar arteries (SCA), and left and right posterior cerebral arteries (PCA) [2]. Abnormal hemodynamic parameters (e.g., low wall shear stress, WSS; high oscillatory shear index, OSI; and high transverse WSS, transWSS) have been found to contribute to the incidence and progression of atherosclerosis [5,6,7,8]. Computational fluid dynamic (CFD) methods have been used to extensively investigate the distribution of hemodynamic parameters near the anastomosis of BA and VAs [9,10,11,12,13,14]. There is, lack of patient-specific hemodynamic studies in the vertebrobasilar system including VAs, AICA, BA, SCAs and PCAs

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