Abstract T MP29: Contrast-Enhanced Ultrasound is Useful for Detection of Vulnerable Plaques

Background and Purpose: Vulnerable plaques of carotid arteries are characterized as the presence of large necrotic core, intraplaque hemorrhage (IPH), intraplaque neovascularization (IPN), and active inflammation with thin fibrous cap. MRI is widely used for the qualitative evaluation of the plaques in vivo and the high-intensity plaques (HIP) on magnetization-prepared rapid acquisition with gradient echo (MPRAGE) images indicate containing necrotic cores with IPH, which indicates vulnerable plaques. However, we encounter the symptomatic cases without the presence of HIP on MPRAGE in clinical practice. Recent studies showed the efficacy for the evaluation of IPN using contrast-enhanced ultrasound (CEUS). We aimed to assess the vulnerability of the plaques without high intensity on MPRAGE images using CEUS. Methods: Between July 2010 and June 2014, we enrolled 69 patients with internal carotid artery stenosis who underwent carotid endarterectomy (CEA) and preoperatively examined CEUS and MRI (MPRAGE). All plaques were evaluated with CEUS and the contrast effects were classified semi-quantitatively (grade 0: absent, 1: small, 2: large, 3: extensive). We also divided the plaques into two groups (HIP group or non-HIP group) based on the signal intensity of the plaques on MPRAGE images. The results of MRI and CEUS were compared with histopathological findings of CEA specimens. Results: Fifty-eight plaques of all 69 patients showed HIP (41 were symptomatic), and eleven plaques were non-HIP (five were symptomatic: amaurosis fugax in three, cerebral infarction in two). In non-HIP group, symptomatic plaques were more enhanced (three in grade 2, two in grade 3) than asymptomatic plaques (one in grade 0, five in grade 1) using CEUS. Histopathological findings of all five CEA specimens from symptomatic patients showed that extensive IPN, large necrotic core, and active inflammation with thin fibrous cap which indicated vulnerable plaques, but small amount of IPH. These histological findings were compatible with the results of CEUS and MRI findings. Conclusion: CEUS may be useful for diagnosis of vulnerable plaques without high intensity on MPRAGE images.