Abstract 335: The Association of Carotid Artery Plaque Calcification and Fibrous Cap Status: A High-Resolution Magnetic Resonance Imaging Study
Background: Calcification is a common histological finding in carotid atherosclerosis. However, the role of calcification as a plaque stabilizing feature is controversial. Carotid magnetic resonance imaging (MRI) has been validated with histology to accurately identify calcification, lipid-rich necrotic core, intraplaque hemorrhage, and fibrous cap (FC) status. The purpose of this study was to determine whether calcification in mild to moderate carotid atherosclerosis is associated with a thin or ruptured FC versus a thick FC.
Methods: A total of 80 consecutive subjects with 15–79% carotid stenosis by duplex ultrasound were imaged with a high-resolution, multi-contrast (T1-weighted, proton density, T2-weighted, 3D time of flight, and contrast-enhanced T1) carotid MRI protocol using phase-arrayed surface coils at 1.5T. Two reviewers reached a consensus interpretation for each scan. At each matched axial location, the AHA lesion type was identified and semi-automated image analysis tools were used to measure the area of calcification. At locations with an AHA Type V or VI lesion, FC status was categorized as thick or thin/ruptured using previously established criteria. Chi-square analysis and an independent student’s t-test were used to assess for differences in prevalence and size of calcification between locations with a thick versus thin or ruptured FC.
Results: Of 1,260 axial locations obtained, 392 had either a Type V or VI lesion. In this subset, 157 locations had a thick FC, 235 had a thin or ruptured FC, and calcification was present in 130. The prevalence of calcification in the thin or ruptured FC group was significantly higher than that in the thick FC group (72 % vs. 29%, p=0.001). The mean (SD) size of calcification, however, was not significantly different between groups (5.4 (4.7) vs. 5.0 (5.3) mm2, p=0.71).
Conclusion: The presence of calcification in mild to moderate lesions is associated with having a thin or ruptured FC. These findings indicate calcification may contribute to plaque instability when present in the atherosclerotic lesion. Prospective studies are ongoing to assess whether carotid plaque calcification is associated with an increased risk for stroke.