Abstract
Carotid endarterectomy (CEA) influences the carotid endoluminal anatomy, which results in hemodynamic changes before and after surgery. We investigated the hemodynamics of severe carotid artery stenosis before and after conventional endarterectomy with/without patch repair. An in vitro experiment utilizing carotid phantoms, which underwent a procedure that emulated CEA with/without the patch repair, was performed with a high-spatiotemporal resolution using 4D flow MRI. We evaluated an abnormal region of carotids, which consists of the normalized time-averaged wall shear stress (NTA|WSS|) and the oscillatory shear index (OSI), to account for continuous high-shear regions (high NTA|WSS| and low OSI) and chaotic low-shear regions, i.e., stenosis-prone regions (low NTA|WSS| and high OSI). The use of normalized hemodynamic parameters (e.g., NTA|WSS|) allowed comparison of diverse cases with different conditions of hemodynamics and vessel geometry. We observed that the stenosis-prone regions of the carotids with patches were noticeably larger than the corresponding regions in no-patch carotids. A large recirculating flow zone found in the stenosis-prone region of the internal carotid artery (ICA) of the postoperative carotids with patches partially blocks the flow path into ICA, and consequently the flow rate was not recovered after surgery unlike an expectation.
Highlights
The relationship between pathophysiology of the vascular atherosclerosis and its vascular hemodynamic effects has been studied using various methods for decades[1,2,3,4,5,6]
The pulsatile flow was measured with 4D flow magnetic resonance imaging (MRI), and the volumetric velocity distribution and hemodynamic parameters, such as a combined parameter of WSS and oscillatory shear index (OSI), were visualized and compared before and after carotid endarterectomy (CEA) to assess the changes in hemodynamic characteristics
Comparing the pre- and postoperative carotids, the chaotic low-shear region in the internal carotid artery (ICA) bulb resulted from the recovery of the lumen following the CEA
Summary
The relationship between pathophysiology of the vascular atherosclerosis and its vascular hemodynamic effects has been studied using various methods for decades[1,2,3,4,5,6]. Studies have been conducted on the changes in the volumetric hemodynamics of the carotid artery resulting from endarterectomy with and without patch repair using computational fluid dynamics (CFD). To the best of our knowledge, the changes in volumetric carotid hemodynamics before and after conventional CEA and the comparison of the outcomes with and without patch repairs have seldom yet been investigated in detail using 4D flow MRI. We investigated the volumetric hemodynamics of severe carotid artery stenosis before and after conventional endarterectomy comparing the two cases with and without patch repairs. The pulsatile flow was measured with 4D flow MRI, and the volumetric velocity distribution and hemodynamic parameters, such as a combined parameter of WSS and OSI, were visualized and compared before and after CEA to assess the changes in hemodynamic characteristics
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