Aim: Inflammation is highlighted in the pathogenesis and destabilization of atherosclerotic lesions. Noninvasive identification of inflammation of atherosclerotic lesions has been challenging. 18-Fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) is a useful technique for detecting inflamed atherosclerotic plaques in vivo. However, it is time consuming, expensive, and accompanied by radiation. Therefore, we investigated the relationship between levels of circulating inflammatory markers and the degree of inflammation of atherosclerotic plaques shown by 18F-FDG uptake. We aimed to identify high-risk patients with inflamed, unstable atherosclerotic plaques on the basis of the determination of inflammatory markers.
Methods: The study included 37 patients, 21 with high-grade stenosis of internal carotid artery (ICA group) and 16 with occlusion of common femoral artery (CFA group), who underwent endarterectomy. Mean age of the study population was 69.43±6.2 years. Eight out of 21 patients with ICA stenosis and all patients with CFA occlusion were symptomatic. In all patients before endarterectomy, 18F-FDG-PET imaging was performed and blood samples were obtained for determination of circulating inflammatory markers: high-sensitivity C-reactive protein (hsCRP), tumor necrosis factor alpha (TNF-α), interleukins, and selectins. Both groups were compared with a sex- and age-matched control group composed of 27 healthy volunteers.
Results: 18F-FDG uptake, calculated by target-to-background ratio (TBR) was not significantly different between the groups. Levels of inflammatory markers were elevated, and there were no significant differences between ICA and CFA groups, with an exception of interleukin 6 (IL-6) levels, which was higher in the ICA group (3.2±2.5 ng/L vs. 1.8±1.3 ng/L, p＜0.05). There was a positive interrelationship between 18F-FDG-PET and most of the systemic inflammatory markers: hsCRP (r=0.417, p=0.010), IL-6 (r=0.603, p＜0.001), and TNF-α (r=0.374, p=0.023). However, correlation between 18F-FDG-PET and P-selectin, E-selectin, and t-PA was not found.
Conclusion: Our study showed that an interrelationship exists between the intensity of inflammatory process of atherosclerotic lesions shown by FDG uptake and circulating inflammatory markers. Therefore, the determination of circulating inflammatory markers can have a potential to identify individuals with unstable, inflamed atherosclerotic plaques.