Novel approaches to assessing the signs of atherosclerotic plaque instability in the carotid arteries

Introduction. Application of contrast agents in vascular untrasonography has become a new direction in noninvasive assessment of signs of atherosclerotic plaque (ASP) instability; the type of plaque neovascularization being the major sign. However, questions regarding the accuracy of the methods for quantitative evaluation of plaque neovascularization are still to be answered.

Objective. To evaluate signs of ASP instability in the carotid arteries according to the contrast-enhanced duplex scanning data and to elaborate our own approach to quantitative evaluation of neovascularization.

Materials and methods. Twenty-six patients with carotid atherosclerosis who had been subjected to carotid endarterectomy (n=27) followed by morphological plaque verification were enrolled in this study. All patients underwent standard duplex scanning and scanning using contrast agent SonoVue.

Results. Neovascularization was revealed in all 27 patients with ASP according to the pathomorphological and contrast-enhanced ultrasonography data. The total number of vessels per cm2 of plaque was 6–51 [21±14/cm2] according to the ultrasonography data and 19–1224 [236±249/cm2] according to the pathomorphological examination. According to the ultrasonography data, the absolute values were close to the density of plaque vessels ≥ 30 μm in diameter determined during pathomorphological examination and did not differ significantly from this value (p = 0.67). The morphology data show that vessels <20 μm in diameter, which constituted up to 96% of all microvessels in ASP, cannot be detected by ultrasonography. In one case, ulceration of the ASP surface was detected only by contrast medium injection. Calcified plaques with different degrees of calcination imposed the greatest difficulties when performing ultrasonic assessment of neovascularization.

Conclusions. Contrast-enhanced untrasonography can be used as an informative method to noninvasively detect signs of ASP instability enabling rather accurate assessment of neovascularization at microvessel diameter ≥30 μm. Calcification of ASPs may significantly affect the study results.