Background: Imaging of stroke due to vertebrobasilar dolichoectasia may not reveal either luminal stenosis or atherosclerotic plaque, leading to misdiagnosis of stroke mechanism or etiology. We leveraged the advanced imaging capabilities of computational fluid dynamics (CFD) to disclose the hemodynamic abnormalities within these complex neurovascular lesions.
Methods: CT angiography from a series of stroke patients with vertebrobasilar dolichoectasia was selected from a prospective imaging registry of posterior circulation ischemia. A 3D geometric mesh was generated from CTA source images, extending from distal V4 vertebral arteries (VA) to the P1 posterior cerebral arteries (PCA). CFD processing was conducted with Ansys (ICEM, CFX) on a Cray supercomputer. Boundary conditions applied at the VA inlets and PCA outlets were used to map intraluminal pressure changes (ΔP), blood flow velocities (V), turbulent kinetic energy (TKE) and wall shear stress (WSS).
Results: 18 cases of vertebrobasilar dolichoectasia with CTA source images were processed with CFD. Focal stenoses (>50%) were apparent in only 4/18 (22%) cases.
Intraluminal pressure varied markedly throughout the vertebrobasilar arterial segments in 7/18 (39%) cases. Blood flow velocities were also heterogeneous, with increases in 6/18 (33%) cases and decreases in 5/18 (28%) cases. WSS was markedly abnormal in all 18 cases, revealing regions of both elevated WSS and contralateral decreases in WSS. Maximal TKE values were within expected range for arterial diameter, yet obvious eddy currents were visualized in all 18 cases.
Conclusions: CFD generated from routine CTA reveals numerous hemodynamic abnormalities in vertebrobasilar dolichoectasia, even when stenosis is unapparent. WSS-induced remodeling mapped with CFD may be used to detect arteriogenesis and atherosclerotic lesion development.