Early Enhancement with Contrast-Enhanced Ultrasonography Relates to the Number of Small-Diameter Neovessels in the Carotid Plaque

Intraplaque neovessels (INVs) have been recognized as a major cause of intraplaque hemorrhage and subsequent vulnerability of the carotid plaque. However, the exact mechanisms by which INVs cause intraplaque hemorrhage remain unclear. Various sizes of INVs coexist in carotid plaques pathologically, and we hypothesized that the size of INVs would be associated with carotid plaque histology, particularly in terms of intraplaque hemorrhage. Detection method of INV is important when determining whether carotid plaques are vulnerable, and contrast-enhanced ultrasonography (CEUS) is one of the most useful methods to detect them. The purpose of this study was to examine the relationship between findings from CEUS and vascular pathology obtained by carotid endarterectomy (CEA). We focused on associations between small and large INVs evaluated by CEUS and histologically defined intraplaque hemorrhage.Participants comprised 115 patients (mean age, 73.0 ± 7.2 years; 96 men) who underwent preoperative CEUS and underwent CEA. CEUS findings were evaluated as vascular grade at 0 min (Vas-G0) and 10 min (Vas-G10) after contrast injection. Plaques were histologically evaluated quantitatively for the total area of intraplaque hemorrhage, cholesterol, and calcification and the thinnest fibrous cap. Immunohistochemical studies were conducted using anti-CD-34 antibody as a marker for endothelial cells. INVs were divided into two groups depending on diameter: small INVs, <50 μm; and large INVs, ≥50 μm. The numbers of small and large blood vessels in the plaque were quantified histologically. Associations of small and large INVs with CEUS, plaque histology, and clinical findings were assessed by uni- and multivariable analyses.Multivariable analyses indicated that CEUS Vas-G0 was associated with the 4th quartile of the number of small INVs compared with other quartiles, and Vas-G10 was associated with the 4th quartile of the number of large INVs. Histologically, the presence and area of intraplaque hemorrhage were associated with the number of small INVs, while the increased number of large INVs was associated with infrequent plaque disruption and thicker fibrous cap.Our study showed that early phase enhancement in the CEUS can help identify plaque vulnerability by predicting a larger number of small INVs. This information can also help determine treatment strategies for carotid plaque.