Assessment of coronary atherosclerosis progression and regression at bifurcations using combined IVUS and OCT

Objectives: The aim of this study was to evaluate the progression of atherosclerotic coronary plaques at bifurcations, using combined intravascular ultrasound-virtual histology (IVUS-VH) and optical coherence tomography (OCT).

Background: Pathological findings reveal that atherosclerotic plaques characterized by the presence of large necrotic cores (NCs) with fibrous cap thicknesses < 65 μm are more prone to rupture. Accuracy in the detection of high-risk plaques could be improved by the combined use of IVUS-VH and OCT.

Methods: IVUS-VH and OCT are 2 imaging modalities with different lateral resolutions and different depths of penetration. To provide a precise matching of the images, bifurcations were used as landmarks. IVUS-VH and OCT were performed in 56 bifurcations from 24 patients at baseline and at 6-month follow-up. All patients were treated with standard medical therapy. Bifurcations were studied at the proximal, in-bifurcation, and distal regions. Plaques were classified according to their composition as assessed by IVUS-VH and fibrous cap thickness as quantified by OCT.

Results: At baseline, 27 NC-rich plaques were found. At 6-month follow-up, 22 (81%) did not show any significant change. Four new NC-rich lesions developed. At both time points, percent NC was higher and the fibrous cap was thinner at the proximal bifurcation rim compared with the distal. There were no significant changes in percent NC and fibrous cap thickness in the 3 bifurcation regions between baseline and follow-up examinations. No major cardiovascular events due to bifurcation lesion progression were observed.

Conclusions: The combined use of IVUS-VH and OCT is a reliable tool to serially assess plaque progression and regression, and in the present study it was demonstrated to be safe and feasible. At 6-month follow-up, in this post-percutaneous coronary intervention patient population, most high-risk plaques remained unchanged, retaining their imaging classifications, nevertheless appearing to have remained clinically silent.