Contrast Ultrasound for Vasa Vasorum Imaging: Can We Improve Plaque Risk Stratification?
Vasa vasorum are physiological structures providing nourishment to the vessel wall. Interestingly, they also appear to be involved in both the early and advanced stages of the atherosclerotic process. A proliferation of adventitial vasa vasorum accompanies the initial development of atherosclerotic lesions and, once a plaque is formed, microvessels originating from the adventitia neovascularize the atherosclerotic tissue, contributing to plaque vulnerability. 1
Traditionally, the outer wall, which includes the adventitial layer and the vasa vasorum, has been ascribed a passive role in atherogenesis. In contrast to this view, recent evidence suggests that the adventitial layer may play a significant role in maintaining vessel integrity, and may contribute to the initiation and progression of the atherosclerotic process as well as to the remodeling process. Indeed, experimental studies demonstrated that manipulation of the adventitia and more specifically of the vasa vasorum could lead to atherosclerotic changes of the intima. 2,3 Using microscopic computed tomography (micro-CT) technology, Herrmann and associates have demonstrated that early atherosclerosis is associated with neovascularization of the vasa vasorum. 4 Attenuation and, moreover, regression of the atherosclerotic process with a medical intervention was associated with a decrease in vasa vasorum
density. 5 Yet, although these studies underscore the role of the adventitial vasa vasorum in animal models of atherosclerosis, their involvement in human atherosclerosis has not been fully elucidated.