Inflammatory activity of vulnerable plaques in asymptomatic, non-hemodynamically significant carotid artery stenoses: preliminary results of the carotid artery multi-modality imaging prognostic study

Abstract

Abstract Background [18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a valid technique to quantify carotid plaque inflammation and can improve identification of patients at high risk for stroke. There are few data on the inflammatory plaque activity in asymptomatic patients and of its association with other characteristics of plaque vulnerability. Purpose To assess the inflammatory carotid plaque activity and its correlations with patient characteristics and features of plaque vulnerability detected by other imaging techniques in a population of patients with asymptomatic mild/moderate degree of stenosis. Methods Seventy-five asymptomatic patients with 40-60% unilateral carotid stenosis at Doppler ultrasound (DUS) were prospectively evaluated with [18F]FDG-PET, computed tomography angiography (CTA), and magnetic resonance angiography (MRA). Regions of interests were drawn using fused PET/CT slices on the most diseased segment (MDS), defined as the single hottest slice of [18F]FDG uptake. Background blood pool activity was obtained from regions of interests placed in the lumen of the jugular vein. The target-to-background ratio (TBR) was calculated by dividing maximum standardized uptake value (SUVmax) of the MDS to SUVmax of ipsilateral blood pool activity. Plaque vulnerability was defined as the presence of an echolucent plaque at DUS, plaque ulceration at CTA, intraplaque hemorrhage, and lipid-rich necrotic core at MRA. Results Patients with a TBR ≥median (1.75), compared with those below the median, were significantly more frequently male and on statin therapy, had higher prevalence of ulcerated plaque at CTA (61% vs 35%, p=0.03) and intraplaque hemorrhage at MRA (33% vs 10%, p=0.03), while the prevalence of a lipid-rich necrotic core at MRA was not significantly different (p=0.16). TBR and SUVmax of the MDS were similar in those with or without a ≥50% stenosis, and peak velocities indices at DUS were not significantly correlated with TBR or SUVmax. Log(TBR) was significantly higher in ulcerated, rather than non-ulcerated, plaque (0.27 vs 0.21, p=0.03) and numerically higher in plaques with an intraplaque hemorrhage (0.22 vs 0.30, p=0.06). Log(TBR) and Log(SUVmax) were similar in plaques with and without a lipid-rich necrotic core (p=0.86 for both). Conclusions Higher TBR or SUVmax, indicating a high inflammatory activity, are associated with an ulcerated plaque and the presence of intraplaque hemorrhage but not with either the degree of stenosis or the presence of a lipid-rich necrotic core.