Background and Objective. Currently, pathological jugular valves are thought to be the main cause of altered hemodynamics in the internal jugular veins. The alternative interpretation of flow disturbances in these veins is that nozzle-like strictures in their upper parts, for example caused by enlarged bony processes, are the main source of abnormal outflow. This in silico study was aimed at validation of this hypothesis.
Methods. Computational fluid mechanics software, COMSOL multiphysics, was used. For numerical validation of the real-time blood flow in normal and abnormal veins, the models of these blood vessels were built. The 2-dimensional computational domain involved stenosis at the beginning of the modeled vein and a flexible valve downstream. Dirichlet boundary conditions were applied at the inlet and outlet boundaries of the models. The laminar flow modeling was coupled with structural mechanics, using the fluid-structure interaction approach, where the constitutive relation for blood shear stress to shear strain was considered Newtonian. The material of the venous valve was considered to be isotropic linear elastic.
Results. In the vein models with symmetric 2-leaflet valve and without upstream stenosis or minor stenosis, the flow was undisturbed and laminar. Valve leaflets opened and closed symmetrically, due to the vortices developing downstream of the valve. In the case of major stenosis, with 65% narrowing of the lumen, the centerline velocity was positioned asymmetrically and areas of reverse flow and flow separation developed. These phenomena were seen both in the case of 2-leaflet and 1-leaflet valves. In the 2-leaflet model with major stenosis, vortices evoking flow asymmetry were present at the entire course of the model, while the valve leaflets were distorted by asymmetric flow.
Conclusions. Our computational fluid mechanics modeling suggests that an impaired outflow from the brain through the internal jugular veins is likely to be primarily caused by pathological strictures in their upper parts, instead of pathological jugular valves that of as yet were the main target of clinical research. In addition, pathology of the jugular valves may be exacerbated by the strictures located in the upper segments of these veins.
This dataset contains graphic files that will not be included in the planned paper. Each graphic file is described: which model has been used (eg. Case E - Proximal stenosis with Septum) and at what time the flow has been assessed.
