Evaluation of carotid artery outward remodeling by T1-weighted magnetic resonance imaging in carotid endarterectomy and stenting

Abstract

We evaluated carotid artery outward remodeling and plaque relative signal intensity (rSI) using T1-weighted magnetic resonance imaging (T1-MRI) to investigate their clinical significance in carotid revascularization. From 86 patients undergoing carotid endarterectomy (CEA) or carotid artery stenting (CAS), 88 lesions (51 lesions treated with CEA and 37 lesions treated with CAS) were analyzed retrospectively. We evaluated the preoperative carotid artery remodeling index (CRI), determined by a ratio of the external cross-sectional vessel area at maximum stenosis and the reference cross-sectional vessel area at the distal portion of the internal carotid artery, and the plaque rSI, which is quantified as the ratio between the signal intensities of plaque and adjacent muscle using T1-MRI. We divided carotid lesions into four groups using the median values of CRI and rSI: L/L (CRI < 1.8, rSI < 2.5), H/L (CRI ≥ 1.8, rSI < 2.5), L/H (CRI < 1.8, rSI ≥ 2.5), and H/H (CRI ≥ 1.8, rSI ≥ 2.5). The primary end point was detection of acute ipsilateral ischemia on diffusion-weighted imaging (DWI) within 72 hours of treatment. Mean CRI and rSI were significantly higher in lesions treated with CEA than in those treated with CAS. Postoperative DWI abnormalities were observed in 4 CEA cases (7.8%) and 10 CAS cases (27.0%) (P = .01). In the CAS group, the frequency of DWI abnormalities was 5.5% for the L/L, 40.0% for the H/L and L/H, and 55.5% for the H/H group (P = .009). Multivariate analysis showed that the degree of stenosis and H/H lesion were independent risk factors for cerebral embolism. No correlation was found between plaque parameters and postoperative DWI findings in the CEA group. CRI and rSI provide complementary information for the prediction of high-risk plaques associated with CAS but not with CEA. Preoperative evaluation with T1-MRI facilitates the selection of a treatment strategy for carotid artery stenosis.