Modeling Hemodynamic Effects of the Closure Procedure of Carotid Artery Endarterectomy.

Abstract

Currently, it is unclear why some patients experience restenosis after carotid endarterectomy (CEA) and whether the closing procedure is linked to greater rates of restenosis. Here, the morphology and hemodynamics are compared for the carotid bulb of two patients post-CEA. One carotid bulb was closed with a patch which later suffered a restenosis, while the other patient's bulb was treated using primary closure and did not. Contrast-enhanced magnetic resonance angiography (CE-MRA) was segmented to provide the domain for computational fluid dynamics (CFD). Flowrate waveforms measured with phase-contrast MR were provided for the common carotid artery (CCA) and internal carotid artery (ICA), while only the mean flow rate was provided for the external carotid artery (ECA), requiring the ECA waveform to be calculated. A Womersley profile was applied to the CCA inlet and ECA outlet, with a traction-free boundary condition applied to the ICA outlet. The patch patient who restenosed exhibited a nonphysiological hemodynamic environment that differed from the flow environment observed in the healthy, contralateral bulb. In contrast, the hemodynamics of the primary closure patient who underwent a successful CEA showed more favorable levels and trends of WSS as well as healthy mixing from vortices that were both present in the healthy, contralateral bulb. Changing model parameters such as flow rate, wall compliance, and flow waveforms did not alter these conclusions. Therefore, the geometry of the carotid bulb, as opposed to flow characteristics, seems responsible for the observed differences between these two cases in hemodynamic environments and subsequent outcomes.