Carotid artery atherosclerosis: effect of intensive lipid therapy on the vasa vasorum--evaluation by using dynamic contrast-enhanced MR imaging

Abstract

Purpose: To investigate whether short-term, intensive lipid therapy leads to changes in microvascular characteristics, as measured by using dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging.

Materials and methods: Institutional review board approval and informed consent were obtained for this HIPAA-compatible study. Subjects with established coronary artery disease or carotid artery stenosis of 15% or greater determined by using ultrasonography and with levels of apolipoprotein B of 120 mg/dL (1.2 g/L) or greater were enrolled in an ongoing study (clinical trial NCT00715273). All received intensive lipid therapy to achieve targeted high- and low-density lipoprotein cholesterol levels and underwent serial serum monitoring including high-sensitivity C-reactive protein (HsCRP) level measurements. Carotid artery MR imaging examinations including morphologic and DCE MR images were obtained at baseline and 1 year after treatment. In subjects with advanced lesions (>2 mm thick), MR image analysis was performed, including measurement of lipid-rich necrotic core size and kinetic modeling of DCE MR images to assess changes in the transfer constant (K(trans)). The differences in K(trans) between baseline and 1-year follow-up were compared by using the Wilcoxon signed rank test, and associations were assessed by using the Spearman rank correlation coefficient.

Results: Twenty-eight subjects with interpretable DCE MR imaging results at both baseline and 1-year follow-up were included. After 1 year of treatment, a significant reduction was found in mean K(trans) (0.085 min(-1) ± 0.037 [standard deviation] to 0.067 min(-1) ± 0.028, P = .02). Reduction in K(trans) was not significantly correlated with observed reductions in lipid-rich necrotic core size or reductions in HsCRP level.

Conclusion: These findings suggest that DCE MR imaging may be a useful imaging method for the assessment of the therapeutic response of the vasa vasorum in patients with atherosclerotic plaque.

Figures

Figure 1:

Top: Typical vasa vasorum image from a 46-year-old man. The kinetic modeling results are displayed with vp indicated in red and Ktrans indicated in green. Regions with flowing blood, such as the carotid artery lumen and jugular vein, appear red. Regions with rapid transfer, such as the vessel adventitia (yellow arrows) appear green. Bottom: Representative sequence of DCE MR images obtained before (image frame N = 1) and after bolus injection of the contrast agent gadodiamide (image frames N = 3, N = 5, N = 7, N = 9, and N = 11).

Figure 2:

Change in adventitial Ktrans before and after treatment for 1 year.

Figure 3:

Individual changes in adventitial Ktrans from baseline to year 1. Each line represents one subject (n = 28).

Figure 4:

Vasa vasorum images in a 63-year-old man with hypertension. Adventitial Ktrans was 0.129 min−1 before therapy and 0.099 min−1 after 1- year treatment. There was subtle gradation of color in adventitial zone (arrows).

Figure 5a:

Associations between change in Ktrans and change in (a) lipid-rich necrotic core size or (b) HsCRP levels. Change in Ktrans showed no correlation with change in HsCRP levels (ρ = −0.27, P = .2) or lipid-rich necrotic core size (ρ = 0.08, P = .7).

Figure 5b:

Associations between change in Ktrans and change in (a) lipid-rich necrotic core size or (b) HsCRP levels. Change in Ktrans showed no correlation with change in HsCRP levels (ρ = −0.27, P = .2) or lipid-rich necrotic core size (ρ = 0.08, P = .7).