Association between instability of carotid plaque and coronary plaque assessed by echogenicity using integrated backscatter and Virtual Histology^TM

Abstract

Plaque instability exists at multiple sites in the systemic vascular bed. Assessment of plaque contents could provide useful information on plaque vulnerability. Recently, plaque morphology and composition can be clinically analyzed using Virtual Histology^TM intravascular ultrasound (VH-IVUS). Echolucent carotid plaque with low integrated backscatter (IBS) values has been recognized as lipid-rich, which can predict future cardiovascular complications. We hypothesized that echolucent carotid plaque with low IBS values might be associated with the lipid-rich condition of coronary plaque. We measured maximum intima-media thickening (IMT), plaque score (PS), and echogenicity of carotid plaque using ultrasound with IBS in 14 consecutive patients undergoing coronary intervention. Using VH-IVUS, the coronary plaque component was assessed in a 20mm segment of coronary artery containing the target lesion. In carotid arteries, maximum IMT was 2.1±1.2 mm, plaque score was 8.5±9.0, plaque mean IBS value was -11.4±1.9 dB. In coronary plaque, the percentage of fibrous, fibro-fatty lesion, necrotic core, and dense calcium was 66±9%, 20±9%, 8±6%, and 6±3%, respectively. PS and maximum IMT of carotid plaque were not correlated with coronary plaque component assessed by VH-IVUS. Patients were divided into two groups according to carotid echogenicity: low IBS and high IBS. The percentage of fibro-fatty lesion in coronary plaque was significantly greater in the low IBS group than in the high IBS group (27±2% versus 13±6%, p⟨0.001). By linear regression analysis, the percentage of a combination of fibro-fatty lesion and necrotic core in coronary lesions was significantly correlated with IBS values of carotid plaque (p=0.03). These results indicated that low IBS values in carotid plaque correlated with the lipid-rich condition in coronary plaque. From these results, we concluded that noninvasive qualitative ultrasound evaluation of carotid plaque with IBS is clinically useful to assess coronary plaque vulnerability.