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Calcification of Vascular Smooth Muscle Cells and Imaging of Aortic Calcification and Inflammation
Published on: May 31, 2016
Greater aortic inflammation and calcification in abdominal aortic aneurysmal disease than atherosclerosis: a
Nikhil V Joshi1, Maysoon Elkhawad2, Rachael O Forsythe1
1Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK.
Insights
Patients with abdominal aortic aneurysms (AAA) exhibit heightened aortic inflammation and calcification compared to those with atherosclerosis. Intraluminal thrombus in AAA is linked to reduced inflammation in the adjacent aortic wall.
Area of Science:
- Vascular Biology
- Medical Imaging
- Cardiovascular Disease
Background:
- Abdominal aortic aneurysms (AAA) are associated with inflammation and calcification.
- Understanding the inflammatory profile of AAA is crucial for risk stratification.
Purpose of the Study:
- To compare aortic inflammation and calcification in patients with AAA versus controls with atherosclerosis using PET-CT.
- To investigate the role of intraluminal thrombus in AAA wall inflammation.
Main Methods:
- Prospective recruitment of 63 AAA patients and 19 atherosclerosis controls.
- Assessment of inflammation and calcification using 18F-FDG PET-CT and Agatston scores.
- Quantification via tissue-to-background ratios (TBRs).
Main Results:
- Aneurysmal aortae showed significantly higher 18F-FDG uptake (TBRmax 2.23±0.46) compared to non-aneurysmal aorta (2.12±0.46) and control aortae (1.70±0.22).
- AAA segments had higher calcification (Agatston 4918) than non-aneurysmal segments (1017) and control regions (166).
- Intraluminal thrombus was associated with lower aneurysm wall inflammation (TBRmax 2.14±0.43 vs 2.43±0.45 without thrombus).
Conclusions:
- The entire aorta appears more inflamed in AAA patients, suggesting a generalized inflammatory aortopathy.
- Calcification is concentrated within the AAA sac, with relative sparing of the rest of the aorta.
- Intraluminal thrombus is metabolically inert and reduces inflammation in the adjacent aneurysm wall.
Objective:
Using combined positron emission tomography and CT (PET-CT), we measured aortic inflammation and calcification in patients with abdominal aortic aneurysms (AAA), and compared them with matched controls with atherosclerosis.
Methods:
We prospectively recruited 63 patients (mean age 76.1±6.8 years) with asymptomatic aneurysm disease (mean size 4.33±0.73 cm) and 19 age-and-sex-matched patients with confirmed atherosclerosis but no aneurysm. Inflammation and calcification were assessed using combined 18F-FDG PET-CT and quantified using tissue-to-background ratios (TBRs) and Agatston scores.
Results:
In patients with AAA, 18F-FDG uptake was higher within the aneurysm than in other regions of the aorta (mean TBRmax2.23±0.46 vs 2.12±0.46, p=0.02). Compared with atherosclerotic control subjects, both aneurysmal and non-aneurysmal aortae showed higher 18F-FDG accumulation (total aorta mean TBRmax2.16±0.51 vs 1.70±0.22, p=0.001; AAA mean TBRmax2.23±0.45 vs 1.68±0.21, p<0.0001). Aneurysms containing intraluminal thrombus demonstrated lower 18F-FDG uptake within their walls than those without (mean TBRmax2.14±0.43 vs 2.43±0.45, p=0.018), with thrombus itself showing low tracer uptake (mean TBRmax thrombus 1.30±0.48 vs aneurysm wall 2.23±0.46, p<0.0001). Calcification in the aneurysmal segment was higher than both non-aneurysmal segments in patients with aneurysm (Agatston 4918 (2901-8008) vs 1017 (139-2226), p<0.0001) and equivalent regions in control patients (442 (304-920) vs 166 (80-374) Agatston units per cm, p=0.0042).
Conclusions:
The entire aorta is more inflamed in patients with aneurysm than in those with atherosclerosis, perhaps suggesting a generalised inflammatory aortopathy in patients with aneurysm. Calcification was prominent within the aneurysmal sac, with the remainder of the aorta being relatively spared. The presence of intraluminal thrombus, itself metabolically relatively inert, was associated with lower levels of inflammation in the adjacent aneurysmal wall.
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