Enhanced carotid plaque on contrast-enhanced ultrasound is associated with plaque instability and rupture


Correspondence: Noriko Matsumoto, Department of Stroke Medicine, Kawasaki Medical School, 577 Matsushima, Kurashiki City, Okayama 701-0192, Japan.

E-mail: noripma@med.kawasaki-m.ac.jp

Carotid plaque rupture is closely associated with the degree of neovascularization within the plaque. Recently, the presence of intraplaque neovascularization was demonstrated using contrast-enhanced ultrasound (CEUS) [1]. We investigated the histopathologic findings of enhanced plaque on CEUS in patients who were undergoing carotid endarterectomy (CEA). Between April 2009 and May 2011, we enrolled consecutive 18 patients (16 men, age 69·4 ± 6·7years) who were undergoing CEA. We performed CEUS in all patients before CEA and investigated the association between ultrasound imaging and histopathology of specimens. Sonazoid (Daiich-Sankyo, Tokyo, Japan), perflurobutane microbubbles, was used as the contrast agent. CEUS revealed enhanced plaque in 11 (61·1%) of 18 patients. Enhanced plaque was classified into two sub-groups: a spotty pattern as moving bright spots within plaque; and a linear pattern, where enhanced lesions appeared as a line from intima into plaque (Fig. 1). Only a spotty pattern was observed in five patients, whereas both a spotty and linear pattern were observed in six patients. The amount of neovascularization was larger in enhanced than in non-enhanced plaque (6·79 ± 5·17/2·5 mm2 vs. 1·12 ± 0·90/2·5 mm2, P = 0·001). Furthermore, the enhanced group had more macrophage aggregation (7·76 ± 3·70% vs. 4·23 ± 1·63%, P = 0·030) and intraplaque haemorrhage (18·84 ± 14·88% vs. 5·52 ± 9·68%, P = 0·013) compared with the non-enhanced group. Thin fibrous cap (<200 μm) was more frequent in enhanced than non-enhanced plaque (100% vs. 28·6%, P = 0·002). All of the enhanced plaques with a linear pattern had fibrous cap rupture, but this was observed in only 20% of those with a spotty pattern (P = 0·015). Enhanced plaque on CEUS indicates vulnerable plaque. A linear pattern of enhanced plaque indicates plaque rupture. Enhanced plaque on CEUS should become a new surrogate marker of vulnerable carotid plaque.

Figure 1.

Ultrasound imaging and histopathological findings of a linear pattern in a case with enhanced plaque (linear pattern). Panel a: Contrast-enhanced ultrasound imaging of carotid plaque. Linear enhancement can be detected by contrast-enhanced ultrasound imaging (arrows). Panel b: Low-power photomicrograph of histological section (elastica- M asson stain, original magnification ×2). The photomicrograph showed that fibrous cap was ruptured (arrow). Panel c: Photomicrograph showed that many vessels are present (CD34 immunostaining, original magnification ×2). Panel d: Photomicrograph showed that a large amount of macrophages are present (CD68 immunostaining, original magnification ×2).