Morphologic characteristics of plaque composition have been proposed to explain the apparent paradox of improved clinical events despite no or minimal reduction in % stenosis with statins. CMR can distinguish underlying features that determine plaque ‘vulnerability’. We hypothesize that in statin-naive pts with high-grade carotid artery stenosis, there will be a high degree of correlation in the relationship between the ‘unstable’ lipid pool and ‘stable’ fibrous plaque by 3D CMR, yet may be independent of 2D %stenosis. Representing 530-two mm contiguous CMR (1.5T GE)
in vivo
slices of advanced (mean 61±24% stenosis) carotid disease, 26 complete bilateral human (age: 66±14yrs) plaques were analyzed for 3D volumetric extent of vascular wall: lipid pool, fibrous cap, matrix and minima/maxima of each. All were related to fasting lipid levels relative to %stenosis via QPlaque (Medis, The Netherlands). Plaque morphology determined by T1, T2/PD CMR. In all, 25/26
in vivo
plaques were imaged. Mean resolution: 1x1x2mm. The mg/dL range of LDL-C was 63–186, HDL-C: 28–59 and TG: 81–213. Lipid pool represented 15±4% while fibrous plaque represented 5±15% of total vessel wall. Total Cholesterol (Chol
T
) and LDL-C were inversely related to minimum vessel wall thickness (r=−0.5 and −0.6, respectively, p<0.05, for both) while only Chol
T
was related to fibrous cap (r=0.6, p<0.01). The Chol
T
/LDL-C ratio was highly related to minimum fibrous plaque thickness (r=0.8, p<0.001). The 3D lipid pool was the only fraction highly correlated (>0.6) with triglycerides (r=0.6, p<0.01). A linear regression relating fibrous cap: vessel wall ratio to non-HDL cholesterol and Chol
T
was highly correlated (r=0.6, 0.7, respectively, p<0.01 for both) but was independent of
in vivo %
stenosis (r=0.1). Relating %stenosis to
any
lipid fraction or ratio showed no relationship. Percent stenosis provides relatively little information about vulnerability of
de novo
, statin-naive carotid plaques. As most current imaging studies concentrate on plaque stenosis, a more appropriate focus on plaque composition provides a more robust quantifiable volumetric metric and may be more indicative of the underlying pathology by high-resolution 3D CMR.
This research has received full or partial funding support from the American Heart Association, AHA National Center.
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