Comparison of angioscopy and histopathology for the evaluation of carotid plaque characteristics: an ex vivo validation study

Intravascular angioscopy is widely used for evaluating plaque characteristics through the plaque color in the coronary artery. This study evaluated whether angioscopy is capable of identifying various plaque morphologies, including necrotic core and intraplaque hemorrhage (IPH) in the carotid artery. Nine patients underwent carotid endarterectomy for carotid artery stenosis, and these specimens were imaged ex vivo by angioscopy within 6 h. An angioscopic examination of carotid plaque evaluated its color intensity as follows: white, yellow, or red. The IPH area, necrotic core area, and fibrous cap thickness was measured on histological sections at each site. A total of 7 plaques were graded as white plaques, 10 as yellow, and 8 as red by angioscopy. The IPH area and the percent area occupied by IPH were larger in red and yellow plaques than in white plaques (10.7 ± 9.3 mm², 9.4 ± 7.8 mm², and 2.2 ± 1.7 mm², respectively, P = 0.074; and 25 ± 10%, 19 ± 13%, and 7 ± 5%, respectively, P = 0.008). Furthermore, the thickness of the fibrous cap was significantly thinner in red plaques than in yellow and white plaques (128 ± 34 µm, 328 ± 136 µm, and 285 ± 102 µm, respectively, P = 0.002). The ROC analysis for predicting a presence of red plaques identified that the optimal cutoff value of fibrous cap thickness was 181 µm (area under the curve = 0.987, 100% sensitivity, 90% specificity). The prevalence of red plaques on intravascular angioscopy may represent the existence of plaques containing relatively larger necrotic core and IPH with a thin fibrous cap.