Lipidic contents within calcified plaques: Characteristics and response to LDL-C<55 mg/dL on multi-modality imaging

Calcified plaques have traditionally been regarded as advanced and quiescent atheroma. However, pathological studies indicate lipid content within calcified plaques, suggesting that calcified plaques may harbor active lipidic contents. This study evaluated lipidic plaque content in calcified lesions in vivo using IVUS, OCT and near-infrared spectroscopy (NIRS).

We analyzed 325 cross-sectional frames at 65 calcified lesions in 58 CAD patients from the REASSURE-NIRS registry (NCT04864171). OCT-derived calcification measures, and the arc of NIRS-derived yellow signals within calcification (YSC) were measured. Plaque features were compared between cross-sectional frames with YSC arc < and ≥63° (=median).

The median calcification arc was 224° (statin = 78 %, LDL-C = 81.5 mg/dL), and 73.8 % of images exhibited calcification arc ≥180°. Any YSC was observed at 84.3 % of analyzed frames. YSC arc ≥63° was associated with thinner (743 ± 276 vs. 882 ± 247 μm, p < 0.001) and deeper calcification (median:50 vs. 30 μm, p = 0.002), whereas the frequency of macrophage (16.6 % vs. 11.7 %, p = 0.265), microvessels (0.6 % vs. 0.6 %, p = 1.000) and cholesterol crystals (1.2 % vs. 0.0 %, p = 0.498) did not differ between two groups. Multivariate analysis identified calcification thickness (β = -0.446, 95 % CI = -0.661-0.231, p < 0.001) as an independent predictor of YSC arc ≥63°, whereas calcification arc (β = 0.000, 95 % CI = -0.001-0.001, p = 0.788) and depth (β = -0.592, 95 % CI = -1.408-0.224, p = 0.155) were not. Notably, LDL-C<55 mg/dL was associated with larger calcification arc (p < 0.001), but the YSC arc was not necessarily smaller despite achieving LDL-C<55 mg/dL (p = 0.671).

Lipidic contents existed at calcified lesions exhibiting thinner calcification. This lipidic feature at calcified lesions less likely undergo changes in response to LDL-C<55 mg/dL.