Association of pooled cohort risk scores with vascular inflammation and coronary artery calcification in Korean adults

Atherosclerosis imaging using PET: Insights and applications

PET imaging is able to harness biological processes to characterise high-risk features of atherosclerotic plaque prone to rupture. Current radiotracers are able to track inflammation, microcalcification, hypoxia, and neoangiogenesis within vulnerable plaque. 18 F-fluorodeoxyglucose (18 F-FDG) is the most commonly used radiotracer in vascular studies and is employed as a surrogate marker of plaque inflammation. Increasingly, 18 F-FDG and other PET tracers are also being used to provide imaging endpoints in cardiovascular interventional trials. The evolution of novel PET radiotracers, imaging protocols, and hybrid scanners are likely to enable more efficient and accurate characterisation of high-risk plaque. This review explores the role of PET imaging in atherosclerosis with a focus on PET tracers utilised in clinical research and the applications of PET imaging to cardiovascular drug development.

Diet-Modulated Lipoprotein Metabolism and Vascular Inflammation Evaluated by 18F-fluorodeoxyglucose Positron Emission Tomography

Vascular inflammation plays a central role in atherosclerosis, from initiation and progression to acute thrombotic complications. Modified low-density lipoproteins (LDLs) and apoB-containing particles stimulate plaque inflammation by interacting with macrophages. Loss of function of high-density lipoprotein (HDL) for preventing LDL particles from oxidative modification in dyslipidemic states may amplify modified LDL actions, accelerating plaque inflammation. Diets are one of the most important factors that can affect these processes of lipoprotein oxidation and vascular inflammation. Recently, ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has emerged as a reliable noninvasive imaging modality for identifying and quantifying vascular inflammation within atherosclerotic lesions based on the high glycolytic activity of macrophages infiltrating active atherosclerotic plaques. Vascular inflammation evaluated by FDG PET has been positively related to metabolic syndrome components and traditional risk factors of cardiovascular disease, including high-sensitivity C-reactive protein, body mass index, and insulin resistance. A positive association of vascular inflammation with endothelial dysfunction, resistin levels, pericardial adipose tissue, and visceral fat area has also been reported. In contrast, HDL cholesterol and adiponectin have been inversely related to vascular inflammation detected by FDG PET. Because of its reproducibility, serial FDG PET shows potential for tracking the effects of dietary interventions and other systemic and local antiatherosclerotic therapies for plaque inflammation.

Association between vascular inflammation and non-alcoholic fatty liver disease: Analysis by 18F-fluorodeoxyglucose positron emission tomography

BACKGROUND

Growing evidence suggests that non-alcoholic fatty liver disease (NAFLD) is associated with cardiovascular disease as well as metabolic syndrome. FDG-PET is a novel imaging technique that detects vascular inflammation, which may reflect rupture-prone vulnerable atherosclerotic plaques.

METHODS

Vascular inflammation was measured as the maximum target-to-background ratio (maxTBR), along with various cardiometabolic risk factors in 51 subjects with NAFLD, and compared with 100 age- and gender-matched subjects without NAFLD. The liver attenuation index (LAI), which was measured using computed tomography, was used as a parameter for the diagnosis of NAFLD.

RESULTS

After adjusting for age and sex, both maxTBR and LAI values were associated with several cardiometabolic risk parameters. Furthermore, there was a significant inter-relationship between LAI and maxTBR values (r=-0.227, P=0.005). Individuals with NAFLD had higher maxTBR values than those without NAFLD (P=0.026), although their carotid intima-media thickness (CIMT) values did not differ. The proportion of subjects with NAFLD showed a step-wise increment following the tertiles of maxTBR values (P for trend=0.015). In multiple logistic regression analysis, maxTBR tertiles were independently associated with NAFLD after adjusting for age, gender, systolic blood pressure, triglycerides, HDL-cholesterol, glucose, BUN, creatinine and homeostasis model assessment of insulin resistance (HOMA-IR) (P=0.030). However, their relationship was attenuated after further adjustment for waist circumference or high sensitive C-reactive protein.

CONCLUSION

Patients with NAFLD have an increased risk for vascular inflammation as measured via FDG-PET/CT even without difference in CIMT. (Clinical trials No. NCT01958411, http://www.clinicaltrials.gov/).