Criteria for instability of atherosclerotic plaques in carotid arteries

Ignatyev I.M.^1,2, Zanochkin A.V.¹, Gafurov M.R.³, Rychkova I.V.⁴, Krivosheeva N.V.⁴, Demidova A.K.⁴

1) Interregional Clinical and Diagnostic Centre,
2) Department of Cardiovascular and Endovascular Surgery, Kazan State Medical University of the RF Ministry of Public Health,
3) Institute of Physics of the Kazan (Volga Region) Federal University of the RF Ministry of Education and Science, Kazan,
4) Pirogov Russian National Research Medical University (RNRMU), Moscow, Russia

The purpose of the study was to determine the criteria for instability of atherosclerotic plaques in carotid arteries with the use of improved and new diagnostic techniques.

The study enrolled a total of 92 patients examined with the help of instrumental methods of diagnosis, including ultrasound triplex scanning, magnetic resonance imaging and multislice computed tomography. All patients were subjected to the operation of carotid endarterectomy in various standard modifications. The specimens of atherosclerotic plaques taken intraoperatively were examined with the help of morphological, immunofluorescent methods, electron paramagnetic resonance, electron microscopy.

A multivariate logistic regression analysis demonstrated that the plaques with an area over 90 mm² (OR 4.05; 95% CI 1.32-13.2; p=0.006), a volume of more than 0.6 cm³ (OR 2.72; 95% CI 1.05-9.58; p=0.04), and the JBA value of not less than 8 mm² (OR 2.82; 95% CI 1.22-6.23; p=0.02) were statistically significant independent predictors of histologically verified unstable plaques. The results were compared to the findings of histological methods. In patients with the above mentioned ultrasonographic parameters, unstable plaques were encountered in 94% of cases.

Immunofluorescent assay demonstrated a significant increase in the number of inflammatory markers (CD68+, CD36+ cells), as well as CD31+ cells as markers of neovasculogenesis in unstable plaques.

According to the findings of electron paramagnetic resonance, bivalent manganese is a marker of plaque instability. Further studies will help reveal the mechanisms of plaque calcification. A decrease in the content of manganese correlated with an increase in the degree of plaque calcification (r=-0.69, p<0.01). This serves as indirect evidence of a destabilizing effect of calcification on plaque stability.

It was demonstrated that ultrasound elastography makes it possible to significantly extend the capabilities of standard ultrasound examination in detecting instability of atherosclerotic plaques in carotid arteries.

KEY WORDS: ultrasound examination, elastography, morphology, immunofluorescent assay, electron paramagnetic resonance, manganese, calcification.

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