Sune Pedersen

Molecular Pathology in Vulnerable Carotid Plaques: Correlation with (18)-Fluorodeoxyglucose Positron Emission Tomography (FDG-PET)

OBJECTIVES Atherosclerosis is recognised as an inflammatory disease, and new diagnostic tools are warranted to evaluate plaque inflammatory activity and risk of cardiovascular events. We investigated [18]-fluorodeoxyglucose (FDG) uptake in vulnerable carotid plaques visualised by positron emission tomography (PET). Uptake was correlated to quantitative gene expression of known markers of inflammation and plaque vulnerability. METHODS Ten patients with recent transient ischaemic attack and carotid artery stenosis (>50%) underwent combined FDG-PET and computed tomography angiography (CTA) the day before carotid endarterectomy. Plaque mRNA expression of the inflammatory cytokine interleukin 18 (IL-18), the macrophage-specific marker CD68 and the two proteinases, Cathepsin K and matrix metalloproteinase 9 (MMP-9), were quantified using real-time quantitative polymerase chain reaction. RESULTS Consistent up-regulation of CD68 (3.8-fold+/-0.9; mean+/-standard error), Cathepsin K (2.1-fold+/-0.5), MMP-9 (122-fold+/-65) and IL-18 (3.4-fold+/-0.7) were found in the plaques, compared to reference-artery specimens. The FDG uptake by plaques was strongly correlated with CD68 gene expression (r=0.71, P=0.02). Any correlations with Cathepsin K, MMP-9 or IL-18 gene expression were weaker. CONCLUSIONS FDG-PET uptake in carotid plaques is correlated to gene expression of CD68 and other molecular markers of inflammation and vulnerability.

Gene expression and 18FDG uptake in atherosclerotic carotid plaques.

PurposeMetabolic assessment of vascular inflammation by 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography (FDG)-PET is a promising new approach for the evaluation of the vulnerability of atherosclerotic plaques. Quantitative real-time PCR allows measurement of gene expression of markers of atherosclerotic plaque vulnerability. These techniques were applied in advanced atherosclerotic disease to relate metabolism and inflammatory activity to the gene expression profile of the vulnerable atherosclerotic plaque. MethodsSeventeen patients with clinical symptoms of cerebral vascular events (<3 months) and an additional ipsilateral internal carotid artery stenosis of greater than 60% were recruited. FDG uptake in the carotids was determined by PET/computed tomography and expressed as mean and maximal standardized uptake values (SUVmean and SUVmax). The atherosclerotic plaques were subsequently recovered by carotid endarterectomy. The gene expression of markers of vulnerability – CD68, IL-18, matrix metalloproteinase 9, cathepsin K, GLUT-1, and hexokinase type II (HK2) – were measured in plaques by quantitative PCR. ResultsIn a multivariate linear regression model, GLUT-1, CD68, cathepsin K, and HK2 gene expression remained in the final model as predictive variables of FDG accumulation calculated as SUVmean (R2=0.26, P<0.0001). In addition, a multivariate linear regression model found GLUT-1, CD68, cathepsin K, and HK2 gene expression as independent predictive variables of FDG accumulation calculated as SUVmax (R2=0.30, P<0.0001). ConclusionGLUT-1, HK2, CD68, and cathepsin K remained in both multivariate models and thus provided independent information regarding FDG uptake. We suggest that FDG uptake is a composite indicator of macrophage load, overall inflammatory activity and collagenolytic plaque destabilization. Accordingly, FDG-PET could prove to be an important predictor of cerebrovascular events in patients with carotid plaques.

18FDG PET and Ultrasound Echolucency in Carotid Artery Plaques

OBJECTIVES The objective was to evaluate inflammation in echolucent carotid artery plaques. BACKGROUND Ultrasound echolucency of carotid artery plaques has been proven to differentiate patients at high risk of stroke. On the other hand, positron emission tomography (PET) of plaques with the use of [(18)F]-fluorodeoxyglucose (FDG) identifies highly inflamed plaques, and the combination of molecular imaging and morphology could improve identification of vulnerable plaques. METHODS A total of 33 patients with cerebrovascular symptoms and carotid artery plaques were included prospectively for ultrasound and PET imaging. Plaque standardized gray scale medians (GSM) were measured in longitudinal ultrasound images to quantitate echolucency, and GSM values were compared with FDG PET uptake quantified by maximum standardized uptake values (SUV). Symptomatic plaques were compared with contralateral carotid artery plaques considered asymptomatic, and in 17 symptomatic patients, endarterectomized plaque specimens were analyzed for CD68 expression. RESULTS There was a negative correlation between GSM and FDG SUV (r = -0.56, p < 0.01). Whereas echo-rich plaques tended to show low FDG uptake, echolucent plaques ranged from high to low inflammatory activity, as depicted with PET. Quantitative FDG SUV differentiated asymptomatic from symptomatic plaques, whereas GSM values did not. There was a positive correlation between CD68 expression and FDG uptake (r = 0.50, p = 0.04). CONCLUSIONS Our results substantiate previous findings of an association between plaque FDG uptake and inflammation. Echolucent plaques exhibit a wide range of inflammatory activity, whereas echorich plaques show little inflammation. FDG PET may be useful for further stratification of echolucent plaques being either active (vulnerable) or inactive.

High-degree atrioventricular block complicating ST-segment elevation myocardial infarction in the era of primary percutaneous coronary intervention

AIMS Primary percutaneous coronary intervention (pPCI) has replaced thrombolysis as treatment-of-choice for ST-segment elevation myocardial infarction (STEMI). However, the incidence and prognostic significance of high-degree atrioventricular block (HAVB) in STEMI patients in the pPCI era has been only sparsely investigated. The objective of this study was to assess the incidence, predictors and prognostic significance of HAVB in STEMI patients treated with pPCI. METHODS AND RESULTS This study included 2073 STEMI patients treated with pPCI. The patients were identified through a hospital register and the Danish National Patient Register. Both registers were also used to establish the diagnosis of HAVB. All-cause mortality was the primary endpoint. During a median follow-up of 2.9 years [interquartile range (IQR) 1.8-4.0] 266 patients died. High-degree atrioventricular block was documented in 67 (3.2%) patients of whom 25 died. Significant independent predictors of HAVB included right coronary artery occlusion, age >65 years, female gender, hypertension, and diabetes. The adjusted mortality rate was significantly increased in patients with HAVB compared to patients without HAVB [hazard ratio = 3.14 (95% confidence interval 2.04-4.84), P< 0.001]. A landmark-analysis 30 days post-STEMI showed equal mortality rates in the two groups. CONCLUSION The incidence of HAVB in STEMI patients treated with pPCI has been reduced compared with reports from the thrombolytic era. However, despite this improvement high-degree AV block remains a severe prognostic marker in the pPCI era. The mortality rate was only increased within the first 30 days. High-degree atrioventricular block patients who survived beyond this time-point thus had a prognosis equal to patients without HAVB.

18F-FDG PET Imaging of Murine Atherosclerosis: Association with Gene Expression of Key Molecular Markers

Aim To study whether 18F-FDG can be used for in vivo imaging of atherogenesis by examining the correlation between 18F-FDG uptake and gene expression of key molecular markers of atherosclerosis in apoE−/− mice. Methods Nine groups of apoE−/− mice were given normal chow or high-fat diet. At different time-points, 18F-FDG PET/contrast-enhanced CT scans were performed on dedicated animal scanners. After scans, animals were euthanized, aortas removed, gamma counted, RNA extracted from the tissue, and gene expression of chemo (C-X-C motif) ligand 1 (CXCL-1), monocyte chemoattractant protein (MCP)-1, vascular cell adhesion molecule (VCAM)-1, cluster of differentiation molecule (CD)-68, osteopontin (OPN), lectin-like oxidized LDL-receptor (LOX)-1, hypoxia-inducible factor (HIF)-1α, HIF-2α, vascular endothelial growth factor A (VEGF), and tissue factor (TF) was measured by means of qPCR. Results The uptake of 18F-FDG increased over time in the groups of mice receiving high-fat diet measured by PET and ex vivo gamma counting. The gene expression of all examined markers of atherosclerosis correlated significantly with 18F-FDG uptake. The strongest correlation was seen with TF and CD68 (p<0.001). A multivariate analysis showed CD68, OPN, TF, and VCAM-1 to be the most important contributors to the uptake of 18F-FDG. Together they could explain 60% of the 18F-FDG uptake. Conclusion We have demonstrated that 18F-FDG can be used to follow the progression of atherosclerosis in apoE−/− mice. The gene expression of ten molecular markers representing different molecular processes important for atherosclerosis was shown to correlate with the uptake of 18F-FDG. Especially, the gene expressions of CD68, OPN, TF, and VCAM-1 were strong predictors for the uptake.

64Cu-DOTATATE PET/MRI for Detection of Activated Macrophages in Carotid Atherosclerotic Plaques Studies in Patients Undergoing Endarterectomy

Objective— A feature of vulnerable atherosclerotic plaques of the carotid artery is high activity and abundance of lesion macrophages. There is consensus that this is of importance for plaque vulnerability, which may lead to clinical events, such as stroke and transient ischemic attack. We used positron emission tomography (PET) and the novel PET ligand [64Cu] [1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid]-d-Phe1,Tyr3-octreotate (64Cu-DOTATATE) to specifically target macrophages via the somatostatin receptor subtype-2 in vivo. Approach and Results— Ten patients underwent simultaneous PET/MRI to measure 64Cu-DOTATATE uptake in carotid artery plaques before carotid endarterectomy. 64Cu-DOTATATE uptake was significantly higher in symptomatic plaque versus the contralateral carotid artery (P<0.001). Subsequently, a total of 62 plaque segments were assessed for gene expression of selected markers of plaque vulnerability using real-time quantitative polymerase chain reaction. These results were compared with in vivo 64Cu-DOTATATE uptake calculated as the mean standardized uptake value. Univariate analysis of real-time quantitative polymerase chain reaction and PET showed that cluster of differentiation 163 (CD163) and CD68 gene expression correlated significantly but weakly with mean standardized uptake value in scans performed 85 minutes post injection (P<0.001 and P=0.015, respectively). Subsequent multivariate analysis showed that CD163 correlated independently with 64Cu-DOTATATE uptake (P=0.031) whereas CD68 did not contribute significantly to the final model. Conclusions— The novel PET tracer 64Cu-DOTATATE accumulates in atherosclerotic plaques of the carotid artery. CD163 gene expression correlated independently with 64Cu-DOTATATE uptake measured by real-time quantitative polymerase chain reaction in the final multivariate model, indicating that 64Cu-DOTATATE PET is detecting alternatively activated macrophages. This association could potentially improve noninvasive identification and characterization of vulnerable plaques.

Intracoronary Compared to Intravenous Bolus Abciximab during Primary Percutaneous Coronary Intervention in ST-segment Elevation Myocardial Infarction (STEMI) Patients Reduces 30-day Mortality and Target Vessel Revascularization: A Randomized Trial

BACKGROUND  Abciximab is beneficial in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (pPCI). However, the optimal administration route of the initial bolus of abciximab, that is, intravenous (IV) versus intracoronary (IC), has been questioned. Preliminary studies suggest that IC-bolus is superior, probably due to high local concentration. In this study, we assess the short-term efficacy and safety of IC compared to IV bolus of abciximab in patients with STEMI during pPCI. METHODS  In 2006-2008, we randomized 355 STEMI patients who underwent pPCI and had indication for abciximab to either IV or IC bolus followed by a 12-hour IV infusion. Primary end-points at 30 days were target vessel revascularization (TVR), recurrent myocardial infarction (MI) or death, and the composite of the three. Secondary end-points were bleeding complications. RESULTS  The two groups (IV n = 170;IC n = 185) were similar with respect to baseline characteristics. Mortality at 30 days was 5.3% in the IV group compared to only 1.1% in the IC group (P = 0.02). TVR was performed in 9.4% in the IV group compared to 3.8% in the IC group (P = 0.03). No significant difference in MI rates was seen (IV 4.7% vs. IC 2.7%; P = 0.32). We found a significant reduction in the composite end-point (IV 19.4% vs. IC 7.6%; P = 0.001) in favor of IC use. Major bleeding complications were similar (IV 2.4% vs. IC 1.6%; P = 0.62). Neither difference was observed in minor bleedings (IV 14.1% vs. IC 9.7%; P = 0.20). CONCLUSION  IC administration of bolus abciximab in STEMI patients undergoing pPCI reduces 30-day mortality and TVR and tends to reduce MI, compared to IV-bolus.

Plasma high-mobility group box 1 levels predict mortality after ST-segment elevation myocardial infarction.

OBJECTIVES We evaluated the potential association between plasma high-mobility group box 1 (HMGB1) levels and outcome in patients with ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention. BACKGROUND The positive effect of reperfusion after STEMI may be compromised by ischemic/reperfusion injury. HMGB1 is released by necrotic cells and, in pre-clinical studies, has been implicated to play a role in myocardial ischemic/reperfusion injury. METHODS The study included 141 STEMI patients, with acute occlusion of the left anterior descending coronary artery successfully treated with percutaneous coronary intervention. Plasma HMGB1 levels were measured by enzyme-linked immunoadsorbent assay at admission. Forty-two healthy individuals served as control subjects. RESULTS After a median of 10 months of follow-up, 13 STEMI patients died. There were no significant differences with regard to baseline variables between the group of patients who survived and those who died. Baseline HMGB1 levels were increased in STEMI patients when compared with control subjects. Furthermore, the STEMI patients who died had higher HMGB1 levels than those who survived. After adjusting for age, sex, troponin I, and creatine kinase-myocardial band, we found that a doubling of HMGB1 concentrations increased the risk of mortality by 75% (hazard ratio: 1.75; 95% confidence interval: 1.1 to 2.8). CONCLUSIONS Plasma HMGB1 levels are elevated in STEMI patients compared with healthy control subjects. Furthermore, after a follow-up period of 10 months, plasma HMGB1 levels are shown to be independently associated with increased mortality in STEMI patients treated with PCI. These data suggest that plasma HMGB1 may be used as a new prognostic biomarker in STEMI patients.

Microvessel Density But Not Neoangiogenesis Is Associated with 18F-FDG Uptake in Human Atherosclerotic Carotid Plaques

IntroductionThe vulnerable atherosclerotic lesion exhibits the proliferation of neovessels and inflammation. The imaging modality 2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography (18FDG-PET) is considered for the identification of vulnerable plaques.PurposeThe purpose of this study was to compare the gene expression of neoangiogenesis and vulnerability-associated genes with 18FDG uptake in patients undergoing carotid endarterectomy.ProceduresHuman atherosclerotic carotid artery plaques from symptomatic patients were used for gene expression analysis by quantitative PCR of vascular endothelial growth factor (VEGF) and integrin αV and integrin β3 subunits, genes essential during neoangiogenesis. We also evaluated the gene expression of CD34, a measure of microvessel density (MVD), as well as CD68, MMP-9, and cathepsin K, genes of major importance in plaque vulnerability. Gene expression analysis was compared with 18FDG-PET.ResultsVEGF and integrin αVβ3 gene expression did not correlate with 18FDG uptake, whereas CD34 gene expression exhibited an inverse correlation with 18FDG uptake. Additionally, we established that markers of vulnerability were correlated with 18FDG uptake.ConclusionsNeoangiogenesis is not associated with 18FDG uptake, whereas MVD and markers of vulnerability correlate with 18FDG uptake. The absence of correlation between markers of neoangiogenesis and 18FDG uptake suggests a temporal separation between the process of neoangiogenesis and inflammatory activity.

Osteoprotegerin predicts long-term outcome in patients with ST-segment elevation myocardial infarction treated with primary percutaneous coronary intervention.

Background: Osteoprotegerin (OPG) is a glycoprotein with a regulatory role in immune, skeletal and vascular systems. Data suggest that high circulating OPG levels are associated with an increased risk of cardiovascular disease. We analyzed the association between OPG and long-term outcome in patients with ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (pPCI). Methods: We included 716 consecutive STEMI patients admitted to a single high-volume invasive heart center from September 2006 to December 2008. Endpoints were all-cause mortality, repeat myocardial infarction, admission due to heart failure and combinations thereof. Median follow-up lasted 27 months (interquartile range: 22–33). Results: OPG levels exhibited a non-Gaussian distribution and were therefore divided into quartiles. High levels of OPG were significantly associated with a worse outcome. After adjustment for conventional risk factors (e.g. C-reactive protein, estimated glomerular filtration rate, symptom-to-balloon time and troponin I) using Cox regression, OPG remained a significantly independent predictor of death (HR per increase in OPG quartile: 1.28; CI: 1.03–1.59; p = 0.03), repeat myocardial infarction (HR: 1.30; CI: 1.00–1.68; p = 0.05) and admission with heart failure (HR: 1.50; CI: 1.18–1.90; p = 0.001). Conclusion: This study shows that OPG independently predicts long-term outcome in STEMI patients treated with pPCI. Eventually, this knowledge could improve risk stratification and overall outcome.