A new method for assessment of plaque vulnerability based on vasa vasorum imaging, by using contrast-enhanced intravascular ultrasound and differential image analysis

Background: Increased neovascularization in vasa vasorum and atherosclerotic plaques has recently been identified as a common feature of inflammation and plaque vulnerability. Microbubble contrast agents, which have been used for intravascular imaging, can be used to trace neovascularization. The aim of the study was to detect and evaluate the density of vasa vasorum in non-culprit coronary atherosclerotic plaques of patients with acute coronary syndrome. Methods: We have studied intravascular ultrasound (IVUS) signals before, during, and after intracoronary injection of microbubbles, proximal to non-culprit atherosclerotic plaques in 16 patients with acute coronary syndrome. Analyses were accomplished using a computational algorithm for the detection of contrast perfusion in such contrast-enhanced sequences. Perfusion density was evaluated by the mean enhancement in the region of interest provided by this difference-imaging technique. Results: Qualitative and quantitative analysis of the pre- and post-injection images showed a significant enhancement in the grey-scale intensity of intima-media and adventitia after injection (intima-media: from 6.0 ± 2.5 to 7.9 ± 3.3%, p = 0.006 and adventitia: from 7.1 ± 2.2 to 7.6 ± 2.5%, p = 0.035). Conclusions: Contrast-enhanced intravascular imaging is a novel, yet clinically available, technique that has the potential to enhance IVUS-based characterization of atherosclerotic plaques. The technique introduces a new perspective to the detection of vulnerable plaques and warrants further investigations.