Morphologic characterization and quantification of superficial calcifications of the coronary artery: In vivo assessment using optical coherence tomography

Coronary calcification is proportional to the extent and severity of atherosclerotic disease, and is a predictor of cardiac events. Furthermore, coronary calcification protruding into the lumen is considered as one type of vulnerable plaque. Optical coherence tomography (OCT) can provide in vivo imaging of the detailed vessel wall structure of the coronary artery with high resolution, as in the histological approach. We analyzed coronary calcification in that fashion using OCT in vivo. This study consisted of 70 superficial coronary calcifications of 39 consecutive patients who underwent percutaneous coronary intervention. After revascularization, OCT was performed in the treated vessel. We analyzed morphologic characteristics and the quantification of OCT-determined coronary calcification. Superficial coronary calcifications were classified into two groups depending on whether they did not intrude the lumen (type I) or did (type II). The distance from the lumen and the volume of each calcification were then measured. Superficial coronary calcifications were classified into two groups; type I, n = 39 (56%) and type II, n = 31 (44%). Type II calcifications were located significantly closer to the lumen [80 μm (60-130) vs.130 μm (90-260), p = 0.015], and tended to be smaller, but did not show a significant difference [0.65 (0.26-1.3) mm³ vs. 1.2 (0.47-1.9) mm3, p = 0.153] compared to those of type I. In conclusion, OCT could visualize superficial coronary calcifications in detail and enable us to evaluate in vivo morphologic characterizations and quantify them.