The axial distribution of lesion-site atherosclerotic plaque components: An in vivo volumetric intravascular ultrasound radiofrequency analysis of lumen stenosis, necrotic core, and vessel remodeling

by Kaple, Ryan Karl

Coronary atherosclerosis is an inflammatory process characterized by lipid accumulation in the vessel intima, an overlying fibrous cap, and a variable amount of lipid and necrotic cellular debris at its core. Percutaneous intravascular ultrasound (IVUS) uses a 3F imaging catheter to provide realtime, in vivo, cross-sectional images of the arterial wall, lumen, and plaque. Radiofrequency analysis of IVUS data characterizes atherosclerotic plaques into necrotic core (NC), dense calcium (DC), fibrofatty (FF), and fibrotic (FI) tissue. We hypothesized that the minimum lumen area (MLA) site will have a different Virtual Histology (VH) IVUS signature than sites proximal or distal. Pre-intervention VH-IVUS was performed in 81 patients (90 de novo lesions: 43 LAD and 47 RCA). Plaque burden, remodeling index, and VH-IVUS plaque composition were assessed throughout the lesion and reference segments as well as at the MLA and maximum (MaxNC) sites. A catheter pullback length of 31.1±12.0mm was used to span a lesion length of 13.8±9.5mm. The MaxNC site was located at the MLA in 3.3% of lesions, proximal to the MLA in 61% of lesions (by 4.11mm) and distal to the MLA in 35.6% of lesions (by 3.56mm). The %DC was greater at the MaxNC and %FI and %FF plaque were less at the MaxNC than at the MLA site. Lesion fibroatheromas (FAs) were more often detected at the MaxNC than the MLA (96% vs 51%) and were more often classified as thin-capped or multilayered than the MLA sites. The remodeling index was greater at the MaxNC than at the MLA sites and correlated with the NC area both at the MLA (r2 0.068, p=0.013) and at the MaxNC (r2 0.074, p=0.009). A greater %DC was found in negatively remodeled vessels at the MLA. In summary, greyscale and VH-IVUS show that the site of greatest potential instability (largest NC and remodeling) is rarely at the MLA, but is most often proximal to the MLA. Also, necrotic core on VH is correlated with remodeling index. These in vivo findings are consistent with previously reported histopathologic data and have important implications for the detection and treatment of coronary artery disease.