Association Between Carotid Artery Perivascular Fat Density and Cerebrovascular Ischemic Events

BACKGROUND: Studies have shown that pericoronary artery inflammation can be accurately detected via increased attenuation on computed tomography. Our purpose was to evaluate the association between pericarotid inflammation, measured by density of carotid perivascular fat on computed tomography angiography, with stroke and transient ischemic attack. METHODS AND RESULTS: We screened computed tomography angiography examinations for patients with unilateral internal carotid artery (ICA) stenosis ≥50% to 99%. A blinded neuroradiologist placed regions‐of‐interest in the pericarotid fat on the slice showing maximal stenosis. Two‐sample t tests were performed to assess between‐subject differences in mean Hounsfield Units in carotid perivascular fat between symptomatic and asymptomatic patients. Paired t tests were used to assess within‐subject differences in mean Hounsfield Units between stenotic versus nonstenotic ICAs in a given patient. We included 94 patients, including 42 symptomatic and 52 asymptomatic patients. In the between‐subject analysis of stenotic ICAs, we found symptomatic patients had higher mean pericarotid fat density compared with asymptomatic patients (−66.2±19.2 versus −77.1±20.4, P=0.009). When comparing nonstenotic ICAs, there was no significant difference between pericarotid fat density in symptomatic compared with asymptomatic patients (−81.0±13.3 versus −85.3±18.0: P=0.198). Within‐subject comparison showed statistically significant increased density in stenotic ICA versus nonstenotic ICA with mean Hounsfield Units difference of 11.1 (P<0.0001). CONCLUSIONS: We found increased density, a surrogate marker for perivascular inflammation, in the fat surrounding ICAs ipsilateral to stroke or transient ischemic attack compared with asymptomatic ICAs. Our findings suggest that inflammation associated with culprit carotid plaques extends beyond the vessel lumen and can be identified using simple methods on computed tomography angiography imaging.