Inflammation Coupling Between Unstable Carotid Plaque and Spleen-A 18F-Fluorodeoxyglucos Positron Emission Tomography Study

Background and purpose: This study was aimed to assess the hypothesis that unstable plaque formation in the carotid artery is one of phenotypes of chronic and systemic inflammation. Methods: This study included 8 symptomatic patients with internal carotid stenosis (ICS) and 7 healthy controls. All subjects underwent F-18-fluorodeoxyglucos positron emission tomography (F-18-FDG PET) of whole body. Plaque vulnerability was evaluated on magnetic resonance imaging (MRI). On F-18-FDG PET, the maximum standardized uptake (SUVmax) value was measured in the carotid plaque, aorta, spleen, liver, and bone marrow. The SUVmax ratio of the spleen or bone marrow to the liver was also calculated. These values were compared between 2 groups. All 8 patients in ICS group underwent carotid endarterectomy, and surgical specimens were subjected to immunohistochemistry. Results: All 8 patients in ICS group had unstable plaque on MRI. The mean SUVmax of carotid plaque was 2.5 +/- .2 in ICS group. The SUVmax of spleen was significantly higher in ICS group than in the controls (3.20 +/- .25 and 2.51 +/- .40, respectively; P = .003). The SUVmax ratio (spleen/liver) was also significantly higher in ICS group than in the controls (1.12 +/- .06 and .85 +/- .12, respectively; P = .001). The SUVmax of aorta was also significantly higher in ICS group than in the controls (2.16 +/- .27 and 1.48 +/- .15, respectively; P = .001). However, there were no significant differences in the SUVmax in the bone marrow and SUVmax ratio (bone marrow/liver) between the 2 groups (P = .811 and P = .731, respectively). Histological examination showed that the plaque strongly expressed endothelial progenitor cells, microvessels, and M1 macrophages. Conclusions: These data strongly suggest the inflammation coupling between the spleen and unstable carotid plaque, and may be useful to develop novel therapeutic strategies against systemic inflammation in patients with ICS.