Abstract 2225: Prevalence of Carotid Atherosclerotic Plaque Composition and Surface Disruption for Different Categories of Normalized Wall Index as Measured by Magnetic Resonance Imaging
INTRODUCTION: Normalized wall index (NWI= wall area/ [lumen area < wall area]) measured by MR imaging (MRI) has been shown to accurately represent carotid atherosclerotic burden. However, little is known about carotid plaque features for different NWI categories. The purpose of this study is to determine the carotid plaque compositions and surface condition for different NWI categories using MRI.
METHODS: Sixty-five patients (mean age 66.7 years; 56 males) with carotid stenosis >50% detected by ultrasound underwent bilateral carotid MRI scans using a GE 3.0T Signa scanner. A standard multi-sequence (time of flight, pre- and post-contrast T1W, PDW, and T2W) carotid artery protocol was used for MR imaging. The areas of wall, lumen, and mean NWI were measured for each artery by two experienced readers. The presence or absence of calcification (CA), necrotic core (NC), intraplaque hemorrhage (IPH) and surface disruption were evaluated for each artery. NWI was partitioned into 5 categories: NWI≤0.4, 0.4<NWI≤0.5, 0.5<NWI≤0.6, 0.6<NWI≤0.7, NWI>0.7. The prevalence of plaque features for each category of NWI was determined.
RESULTS: Ten arteries were excluded because no bifurcation could be identified. Of the remaining 120 arteries (mean NWI, 0.54±0.12), 77.5% had CA, 90.8% had NC, 33.3% had IPH, and 30% showed surface disruption. The prevalence of carotid atherosclerotic plaque compositional features for each NWI category is reported in Table 1⇓. None of the arteries with a NWI=0.4 had IPH or disruption. For arteries with NWI=0.6, 65.7% and 74.3% showed surface disruption and IPH, respectively.
CONCLUSIONS: The prevalence of NC, IPH, and surface disruption progressively increases with NWI. Carotid arteries with NWI≤0.4 do not demonstrate these putative high risk plaque features, whereas these features are common in arteries with a NWI≤0.6. NWI may be helpful to distinguish high risk from low risk plaque in carotid arteries.