Characterization of coronary calcified plaque by using multimodality intravascular imaging
Background: This study aimed to evaluate the lipid contents of calcified plaques (CPs) and their clinical relevance to patients with coronary artery disease using near-infrared spectroscopy (NIRS) with intravascular ultrasound (IVUS) (NIRS-IVUS). Additionally, the morphological characteristics of lipid-containing CPs were assessed using optical coherence tomography (OCT). Methods: This study was a retrospective observational study of consecutive patients who underwent both NIRS-IVUS and OCT. We identified CPs (calcification angle > 45°) using grayscale IVUS and divided them into two groups (lipid group and no lipid group) based on the presence or absence of lipids using NIRS. Results: Lipids were observed in 32 of 103 CPs (31%). During the per-patient analysis, patients with lipid-containing CPs had significantly higher serum total cholesterol levels than those without lipid-containing CPs (p = 0.021). Additionally, during the per-lesion analysis, it was observed that lipids accumulated more in the largest calcification arc of the CP and in adjacent segments in the lipid group than in the no lipid group (Region of interest: p < 0.001; proximal 4mm segment: p = 0.002; distal 4mm segment: p = 0.013). Lesions in the lipid group had more OCT characteristics representing plaque vulnerability, such as macrophages (p < 0.001) and layered plaques (p < 0.001), than those in the no lipid group. A multivariate logistic regression analysis revealed that only CPs with an unclear outer border, as assessed by OCT, were independent predictors of lipid contents within CPs (p < 0.001). Conclusions: Multimodality imaging using NIRS-IVUS and OCT demonstrated that lipid-containing CPs were common in patients with high serum total cholesterol levels and could be identified by their outer borders during OCT imaging.