Assessment of inflammatory burden contralateral to the symptomatic carotid stenosis using high-resolution ultrasmall,
Tjun Tang1, Simon P S Howarth, Sam R Miller
1University Department of Radiology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK.
Background And Purpose:
It is well known that the vulnerable atheromatous plaque has a thin, fibrous cap and large lipid core with associated inflammation. This inflammation can be detected on MRI with use of a contrast medium, Sinerem, an ultrasmall superparamagnetic iron oxide (USPIO). Although the incidence of macrophage activity in asymptomatic disease appears low, we aimed to explore the incidence of MRI-defined inflammation in asymptomatic plaques in patients with known contralateral symptomatic disease.
Methods:
Twenty symptomatic patients underwent multisequence MRI before and 36 hours after USPIO infusion. Images were manually segmented into quadrants, and the signal change in each quadrant was calculated after USPIO administration. A mixed mathematical model was developed to compare the mean signal change across all quadrants in the 2 groups. Patients had a mean symptomatic stenosis of 77% compared with 46% on their asymptomatic side, as measured by conventional angiography.
Results:
There were 11 (55%) men, and the median age was 72 years (range, 53 to 84 years). All patients had risk factors consistent with severe atherosclerotic disease. All symptomatic carotid stenoses had inflammation, as evaluated by USPIO-enhanced imaging. On the contralateral sides, inflammatory activity was found in 19 (95%) patients. Contralaterally, there were 163 quadrants (57%) with a signal loss after USPIO when compared with 217 quadrants (71%) on the symptomatic side (P=0.007).
Conclusions:
This study adds weight to the argument that atherosclerosis is a truly systemic disease. It suggests that investigation of the contralateral side in patients with symptomatic carotid stenosis can demonstrate inflammation in 95% of plaques, despite a mean stenosis of only 46%. Thus, inflammatory activity may be a significant risk factor in asymptomatic disease in patients who have known contralateral symptomatic disease. Patients with symptomatic carotid disease should have their contralateral carotid artery followed up.
Insights
Inflammation is common in asymptomatic carotid plaques, even with mild stenosis, detected by ultrasmall superparamagnetic iron oxide (USPIO)-enhanced MRI. This suggests atherosclerosis is systemic and warrants monitoring of contralateral arteries.
Area of Science:
- Cardiovascular Imaging
- Atherosclerosis Research
- Inflammatory Disease Markers
Background:
- Vulnerable atheromatous plaques feature thin fibrous caps, large lipid cores, and inflammation.
- Ultrasmall superparamagnetic iron oxide (USPIO) contrast agents detect inflammation on MRI.
- Macrophage activity in asymptomatic disease is typically considered low.
Purpose of the Study:
- To determine the incidence of MRI-defined inflammation in asymptomatic carotid plaques.
- To investigate asymptomatic plaques in patients with known contralateral symptomatic disease.
Main Methods:
- Twenty patients with symptomatic carotid stenosis underwent multisequence MRI before and after USPIO infusion.
- Images were segmented, and signal change post-infusion was calculated.
- A mixed mathematical model compared signal change across quadrants.
Main Results:
- All symptomatic carotid stenoses (77% mean stenosis) showed inflammation.
- Inflammatory activity was detected in 95% of asymptomatic contralateral plaques (46% mean stenosis).
- Contralateral plaques showed significantly less signal loss (57%) compared to symptomatic plaques (71%) (P=0.007).
Conclusions:
- Atherosclerosis is a systemic disease, with inflammation prevalent in asymptomatic plaques.
- Investigating the contralateral carotid artery reveals inflammation in 95% of plaques, even with mild stenosis.
- Inflammatory activity in asymptomatic plaques may be a significant risk factor, necessitating follow-up.
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