Amparo L. Figueroa

Feasibility of FDG Imaging of the Coronary Arteries: Comparison Between Acute Coronary Syndrome and Stable Angina

OBJECTIVES This study tested the hypothesis that fluorodeoxyglucose (FDG) uptake within the ascending aorta and left main coronary artery (LM), measured using positron emission tomography (PET), is greater in patients with recent acute coronary syndrome (ACS) than in patients with stable angina. BACKGROUND Inflammation is known to play an important role in atherosclerosis. Positron emission tomography imaging with (18)F-FDG provides a measure of plaque inflammation. METHODS Twenty-five patients (mean age 57.9 +/- 9.8 years, 72% male, 10 ACS, and 15 stable angina) underwent cardiac computed tomographic angiography and PET imaging with (18)F-FDG after invasive angiography. Images were coregistered, and FDG uptake was measured at locations of interest for calculation of target-to-background ratios (TBR). Additionally, FDG uptake was measured at the site of the lesion deemed clinically responsible for the presenting syndrome (culprit) by virtue of locating the stent deployed to treat the syndrome. RESULTS The FDG uptake was higher in the ACS versus the stable angina groups in the ascending aorta (median [interquartile ranges] TBR 3.30 [2.69 to 4.12] vs. 2.43 [2.00 to 2.86], p = 0.02), as well as the LM (2.48 [2.30 to 2.93] vs. 2.00 [1.71 to 2.44], p = 0.03, respectively). The TBR was greater for culprit lesions associated with ACS than for lesions stented for stable coronary syndromes (2.61 vs. 1.74, p = 0.02). Furthermore, the TBR in the stented lesions (in ACS and stable angina groups) correlated with C-reactive protein (r = 0.58, p = 0.04). CONCLUSIONS This study shows that in patients with recent ACS, FDG accumulation is increased both within the culprit lesion as well as in the ascending aorta and LM. This observation suggests inflammatory activity within atherosclerotic plaques in acute coronary syndromes and supports intensification of efforts to refine PET methods for molecular imaging of coronary plaques.

Positron emission tomography measurement of periodontal 18F-fluorodeoxyglucose uptake is associated with histologically determined carotid plaque inflammation.

OBJECTIVES This study aimed to test the hypothesis that metabolic activity within periodontal tissue (a possible surrogate for periodontal inflammation) predicts inflammation in a remote atherosclerotic vessel, utilizing (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging. BACKGROUND Several lines of evidence establish periodontal disease as an important risk factor for atherosclerosis. FDG-PET imaging is an established method for measuring metabolic activity in human tissues and blood vessels. METHODS One hundred twelve patients underwent FDG-PET imaging 92 ± 5 min after FDG administration (13 to 25 mCi). Periodontal FDG uptake was measured by obtaining standardized uptake values from the periodontal tissue of each patient, and the ratio of periodontal to background (blood) activity was determined (TBR). Standardized uptake value measurements were obtained in the carotid and aorta as well as in a venous structure. Localization of periodontal, carotid, and aortic activity was facilitated by PET coregistration with computed tomography or magnetic resonance imaging. A subset of 16 patients underwent carotid endarterectomy within 1 month of PET imaging, during which atherosclerotic plaques were removed and subsequently stained with anti-CD68 antibodies to quantify macrophage infiltration. Periodontal FDG uptake was compared with carotid plaque macrophage infiltration. RESULTS Periodontal FDG uptake (TBR) is associated with carotid TBR (R = 0.64, p < 0.0001), as well as aortic TBR (R = 0.38; p = 0.029). Moreover, a strong relationship was observed between periodontal TBR and histologically assessed inflammation within excised carotid artery plaques (R = 0.81, p < 0.001). CONCLUSIONS FDG-PET measurements of metabolic activity within periodontal tissue correlate with macrophage infiltration within carotid plaques. These findings provide direct evidence for an association between periodontal disease and atherosclerotic inflammation.

Distribution of Inflammation Within Carotid Atherosclerotic Plaques With High-Risk Morphological Features A Comparison Between Positron Emission Tomography Activity, Plaque Morphology, and Histopathology

Background— Several high-risk morphological features (HRM) of plaques, especially in combination, are associated with an increased risk of a clinical event. Although plaque inflammation is also associated with atherothrombosis, the relationship between inflammation and number of HRM is not well understood. Methods and Results— Thirty-four patients underwent 18flurodeoxyglucose positron emission tomography (FDG-PET) imaging, and carotid atherosclerotic inflammation was assessed (target-to-background ratio). Additionally, in a subset of 10 subjects with carotid stenosis who underwent carotid endarterectomy, inflammation was histologically assessed (CD68 staining). Vessel wall morphology was examined using computed tomography for the presence of visible plaque and presence of 3 HRM: positive remodeling, luminal irregularity, and low attenuation. A total of 100 vascular segments were analyzed, of which 69 contained visible plaque (26 plaques with ≥1 HRM). Inflammation, by FDG uptake (target-to-background ratio), was higher in plaques with (versus without) HRM (mean±SEM: 2.21±0.20 versus 1.66±0.07, P=0.0003) and increased with the number of HRM observed (P<0.001 for trend). Similarly, inflammation within atherosclerotic specimens (% CD68 staining) was higher in plaques with (versus without) HRM (median [interquartile range]: 10 [0, 19.85] versus 0 [0, 1.55], P=0.01) and increased with the number of HRM observed (P<0.001 for trend). Conclusions— Inflammation, as assessed by both FDG uptake and histology, is increased in plaques containing HRM and increases with increasing number of HRM. These data support the concept that inflammation accumulates relative to the burden of morphological abnormalities.Background— Several high-risk morphological features (HRM) of plaques, especially in combination, are associated with an increased risk of a clinical event. Although plaque inflammation is also associated with atherothrombosis, the relationship between inflammation and number of HRM is not well understood. Methods and Results— Thirty-four patients underwent 18flurodeoxyglucose positron emission tomography (FDG-PET) imaging, and carotid atherosclerotic inflammation was assessed (target-to-background ratio). Additionally, in a subset of 10 subjects with carotid stenosis who underwent carotid endarterectomy, inflammation was histologically assessed (CD68 staining). Vessel wall morphology was examined using computed tomography for the presence of visible plaque and presence of 3 HRM: positive remodeling, luminal irregularity, and low attenuation. A total of 100 vascular segments were analyzed, of which 69 contained visible plaque (26 plaques with ≥1 HRM). Inflammation, by FDG uptake (target-to-background ratio), was higher in plaques with (versus without) HRM (mean±SEM: 2.21±0.20 versus 1.66±0.07, P =0.0003) and increased with the number of HRM observed ( P <0.001 for trend). Similarly, inflammation within atherosclerotic specimens (% CD68 staining) was higher in plaques with (versus without) HRM (median [interquartile range]: 10 [0, 19.85] versus 0 [0, 1.55], P =0.01) and increased with the number of HRM observed ( P <0.001 for trend). Conclusions— Inflammation, as assessed by both FDG uptake and histology, is increased in plaques containing HRM and increases with increasing number of HRM. These data support the concept that inflammation accumulates relative to the burden of morphological abnormalities.

Relation between resting amygdalar activity and cardiovascular events: a longitudinal and cohort study

BACKGROUND Emotional stress is associated with increased risk of cardiovascular disease. We imaged the amygdala, a brain region involved in stress, to determine whether its resting metabolic activity predicts risk of subsequent cardiovascular events. METHODS Individuals aged 30 years or older without known cardiovascular disease or active cancer disorders, who underwent 18F-fluorodexoyglucose PET/CT at Massachusetts General Hospital (Boston, MA, USA) between Jan 1, 2005, and Dec 31, 2008, were studied longitudinally. Amygdalar activity, bone-marrow activity, and arterial inflammation were assessed with validated methods. In a separate cross-sectional study we analysed the relation between perceived stress, amygdalar activity, arterial inflammation, and C-reactive protein. Image analyses and cardiovascular disease event adjudication were done by mutually blinded researchers. Relations between amygdalar activity and cardiovascular disease events were assessed with Cox models, log-rank tests, and mediation (path) analyses. FINDINGS 293 patients (median age 55 years [IQR 45·0-65·5]) were included in the longitudinal study, 22 of whom had a cardiovascular disease event during median follow-up of 3·7 years (IQR 2·7-4·8). Amygdalar activity was associated with increased bone-marrow activity (r=0·47; p<0·0001), arterial inflammation (r=0·49; p<0·0001), and risk of cardiovascular disease events (standardised hazard ratio 1·59, 95% CI 1·27-1·98; p<0·0001), a finding that remained significant after multivariate adjustments. The association between amygdalar activity and cardiovascular disease events seemed to be mediated by increased bone-marrow activity and arterial inflammation in series. In the separate cross-sectional study of patients who underwent psychometric analysis (n=13), amygdalar activity was significantly associated with arterial inflammation (r=0·70; p=0·0083). Perceived stress was associated with amygdalar activity (r=0·56; p=0·0485), arterial inflammation (r=0·59; p=0·0345), and C-reactive protein (r=0·83; p=0·0210). INTERPRETATION In this first study to link regional brain activity to subsequent cardiovascular disease, amygdalar activity independently and robustly predicted cardiovascular disease events. Amygdalar activity is involved partly via a path that includes increased bone-marrow activity and arterial inflammation. These findings provide novel insights into the mechanism through which emotional stressors can lead to cardiovascular disease in human beings. FUNDING None.

Focal Arterial Inflammation Precedes Subsequent Calcification in the Same Location A Longitudinal FDG-PET/CT Study

Background— Arterial calcium (Ca) deposition has been identified as an active inflammatory process. We sought to test the hypothesis that local vascular inflammation predisposes to subsequent arterial calcium deposition in humans. Methods and Results— From a hospital database, we identified 137 patients (age, 61±13 years; 48.1% men) who underwent serial positron-emission tomography/computed tomography (1–5 years apart). Focal arterial inflammation was prospectively determined by measuring 18F-flourodeoxyglucose uptake (using baseline positron-emission tomography) within predetermined locations of the thoracic aortic wall and was reported as a standardized uptake value. A separate, blinded investigator evaluated calcium deposition (on the baseline and follow-up computed tomographic scans) along the same standardized sections of the aorta. New calcification was prospectively defined using square root–transformed difference of calcium volume score, with a cutoff value of 2.5. Accordingly, vascular segment was classified as either with or without subsequent calcification. Overall, 67 (9%) of aortic segments demonstrated subsequent calcification. Baseline median (interquartile range) standardized uptake value was higher in segments with versus without subsequent calcification (2.09 [1.84–2.44] versus 1.92 [1.72–2.20], P=0.002). This was also true in the subset of segments with Ca present at baseline (2.08 [1.81–2.40] versus 1.86 [1.66–2.09], P=0.02), as well as those without (2.17 [1.87–2.51] versus 1.93 [1.73–2.20], P=0.04). Furthermore, across all patients, subsequent Ca deposition was associated with the underlying 18F-flourodeoxyglucose uptake (inflammatory signal), measured as standardized uptake value (odds ratio [95% confidence interval]=2.94 [1.27–6.89], P=0.01) or target-to-background ratio (2.59 [1.18–5.70], P=0.02), after adjusting for traditional cardiovascular risk factors. Conclusions— Here, we provide first-in-man evidence that arterial inflammation precedes subsequent Ca deposition, a marker of plaque progression, within the underlying location in the artery wall.

Imaging of the Aortic Valve Using Fluorodeoxyglucose Positron Emission Tomography: Increased Valvular Fluorodeoxyglucose Uptake in Aortic Stenosis

OBJECTIVES Because fluorodeoxyglucose positron emission tomography (FDG-PET) imaging provides a noninvasive index of inflammation, we sought to assess whether FDG uptake in the aortic valve (AV) is increased in aortic stenosis (AS). BACKGROUND AS is associated with valvular inflammation. METHODS FDG-PET/computed tomography data were retrospectively evaluated in 84 patients (age 73 ± 9 years, 45% female), 42 patients with AS, and 42 age-matched controls. FDG uptake was determined within the AV while blinded to AS severity. Target-to-background ratio (TBR) was calculated as valvular/blood activity. Stenosis severity was established on echocardiography, and presence of AV calcification was independently assessed on computed tomography. RESULTS The aortic valve PET signal (TBR) was increased in AS compared with controls (median 1.53 [interquartile range (IQR): 1.42 to 1.76] vs. 1.34 [IQR: 1.20 to 1.55]; p < 0.001). Further, compared with controls, TBR was increased in mild (median 1.50 [IQR: 1.36 to 1.75]; p = 0.01) and moderate (median 1.70 [IQR: 1.52 to 1.94]; p < 0.001), but not in severe AS (median 1.49 [IQR: 1.40 to 1.54]; p = 0.08). When subjects were categorized according to AV calcification, valvular FDG uptake was increased in mildly (median 1.50 [IQR: 1.36 to 1.79]; p < 0.01) and moderately (median 1.67 [IQR: 1.50 to 1.85]; p < 0.001), but not severely calcified valves (median 1.51 [IQR: 1.38 to 1.54]; p = 0.15), compared with noncalcified valves (median 1.35 [IQR: 1.20 to 1.52]). CONCLUSIONS This study supports the hypothesis that AS is an inflammatory condition and suggests that inflammation may be reduced in late-stage disease. This may have important implications in the design of studies assessing the effect of therapeutic agents in modifying progression of AS.

Nonpharmacological Lipoprotein Apheresis Reduces Arterial Inflammation in Familial Hypercholesterolemia

BACKGROUND Patients with familial hypercholesterolemia (FH) are characterized by elevated atherogenic lipoprotein particles, predominantly low-density lipoprotein cholesterol (LDL-C), which is associated with accelerated atherogenesis and increased cardiovascular risk. OBJECTIVES This study used (18)F-fluorodeoxyglucose positron emission tomography ((18)FDG-PET) to investigate whether arterial inflammation is higher in patients with FH and, moreover, whether lipoprotein apheresis attenuates arterial wall inflammation in FH patients. METHODS In total, 38 subjects were recruited: 24 FH patients and 14 normolipidemic controls. All subjects underwent FDG-PET imaging at baseline. Twelve FH patients who met the criteria for lipoprotein apheresis underwent apheresis procedures followed by a second FDG-PET imaging 3 days (range 1 to 4 days) after apheresis. Subsequently, the target-to-background ratio (TBR) of FDG uptake within the arterial wall was assessed. RESULTS In FH patients, the mean arterial TBR was higher compared with healthy controls (2.12 ± 0.27 vs. 1.92 ± 0.19; p = 0.03). A significant correlation was observed between baseline arterial TBR and LDL-C (R = 0.37; p = 0.03) that remained significant after adjusting for statin use (β = 0.001; p = 0.02) and atherosclerosis risk factors (β = 0.001; p = 0.03). LDL-C levels were significantly reduced after lipoprotein apheresis (284 ± 118 mg/dl vs. 127 ± 50 mg/dl; p < 0.001). There was a significant reduction of arterial inflammation after lipoprotein apheresis (TBR: 2.05 ± 0.31 vs. 1.91 ± 0.33; p < 0.02). CONCLUSIONS The arterial wall of FH patients is characterized by increased inflammation, which is markedly reduced after lipoprotein apheresis. This lends support to a causal role of apoprotein B-containing lipoproteins in arterial wall inflammation and supports the concept that lipoprotein-lowering therapies may impart anti-inflammatory effects by reducing atherogenic lipoproteins.

Relationship Between Measures of Adiposity, Arterial Inflammation, and Subsequent Cardiovascular Events

Background—The objective of this study was to evaluate how different measures of adiposity are related to both arterial inflammation and the risk of subsequent cardiovascular events. Methods and Results—We included individuals who underwent 18F-fluorodeoxyglucose positron emission tomography/computed tomography imaging for oncological evaluation. Subcutaneous adipose tissue (SAT) volume, visceral adipose tissue (VAT) volume, and VAT/SAT ratio were determined. Additionally, body mass index, metabolic syndrome, and aortic 18F-fluorodeoxyglucose uptake (a measure of arterial inflammation) were determined. Subsequent development of cardiovascular disease (CVD) events was adjudicated. The analysis included 415 patients with a median age of 55 (P25–P75: 45–65) and a median body mass index of 26.4 (P25–P75: 23.4–30.9) kg/m2. VAT and SAT volume were significantly higher in obese individuals. VAT volume (r=0.290; P<0.001) and VAT/SAT ratio (r=0.208; P<0.001) were positively correlated with arterial inflammation. Thirty-two subjects experienced a CVD event during a median follow-up of 4 years. Cox proportional hazard models showed that VAT volume and VAT/SAT ratio were associated with CVD events (hazard ratio [95% confidence interval]: 1.15 [1.06–1.25]; P<0.001; 3.60 [1.88–6.92]; P<0.001, respectively). Body mass index, metabolic syndrome, and SAT were not predictive of CVD events. Conclusions—Measures of visceral fat are positively related to arterial inflammation and are independent predictors of subsequent CVD events. Individuals with higher measures of visceral fat as well as elevated arterial inflammation are at highest risk for subsequent CVD events. The findings suggest that arterial inflammation may explain some of the CVD risk associated with adiposity.

Distribution of Inflammation within Carotid Atherosclerotic Plaques with High Risk Morphological Features: A Comparison Between PET Activity, Plaque Morphology and Histopathology

Background— Several high-risk morphological features (HRM) of plaques, especially in combination, are associated with an increased risk of a clinical event. Although plaque inflammation is also associated with atherothrombosis, the relationship between inflammation and number of HRM is not well understood. Methods and Results— Thirty-four patients underwent 18flurodeoxyglucose positron emission tomography (FDG-PET) imaging, and carotid atherosclerotic inflammation was assessed (target-to-background ratio). Additionally, in a subset of 10 subjects with carotid stenosis who underwent carotid endarterectomy, inflammation was histologically assessed (CD68 staining). Vessel wall morphology was examined using computed tomography for the presence of visible plaque and presence of 3 HRM: positive remodeling, luminal irregularity, and low attenuation. A total of 100 vascular segments were analyzed, of which 69 contained visible plaque (26 plaques with ≥1 HRM). Inflammation, by FDG uptake (target-to-background ratio), was higher in plaques with (versus without) HRM (mean±SEM: 2.21±0.20 versus 1.66±0.07, P=0.0003) and increased with the number of HRM observed (P<0.001 for trend). Similarly, inflammation within atherosclerotic specimens (% CD68 staining) was higher in plaques with (versus without) HRM (median [interquartile range]: 10 [0, 19.85] versus 0 [0, 1.55], P=0.01) and increased with the number of HRM observed (P<0.001 for trend). Conclusions— Inflammation, as assessed by both FDG uptake and histology, is increased in plaques containing HRM and increases with increasing number of HRM. These data support the concept that inflammation accumulates relative to the burden of morphological abnormalities.Background— Several high-risk morphological features (HRM) of plaques, especially in combination, are associated with an increased risk of a clinical event. Although plaque inflammation is also associated with atherothrombosis, the relationship between inflammation and number of HRM is not well understood. Methods and Results— Thirty-four patients underwent 18flurodeoxyglucose positron emission tomography (FDG-PET) imaging, and carotid atherosclerotic inflammation was assessed (target-to-background ratio). Additionally, in a subset of 10 subjects with carotid stenosis who underwent carotid endarterectomy, inflammation was histologically assessed (CD68 staining). Vessel wall morphology was examined using computed tomography for the presence of visible plaque and presence of 3 HRM: positive remodeling, luminal irregularity, and low attenuation. A total of 100 vascular segments were analyzed, of which 69 contained visible plaque (26 plaques with ≥1 HRM). Inflammation, by FDG uptake (target-to-background ratio), was higher in plaques with (versus without) HRM (mean±SEM: 2.21±0.20 versus 1.66±0.07, P =0.0003) and increased with the number of HRM observed ( P <0.001 for trend). Similarly, inflammation within atherosclerotic specimens (% CD68 staining) was higher in plaques with (versus without) HRM (median [interquartile range]: 10 [0, 19.85] versus 0 [0, 1.55], P =0.01) and increased with the number of HRM observed ( P <0.001 for trend). Conclusions— Inflammation, as assessed by both FDG uptake and histology, is increased in plaques containing HRM and increases with increasing number of HRM. These data support the concept that inflammation accumulates relative to the burden of morphological abnormalities.

INCREASED BONE MARROW METABOLIC ACTIVITY IS ASSOCIATED WITH INCREASED RISK OF FUTURE CARDIOVASCULAR EVENTS

Bone marrow (BM) metabolic activity is increased after ACS and is associated with release of pro-inflammatory leukocytes and arterial inflammation. However, the relationship of BM activity to cardiovascular disease (CVD) events remains unknown. We identified 513 individuals free of cancer or prior