In Vivo Calcium Detection by Comparing Optical Coherence Tomography, Intravascular Ultrasound, and Angiography

The aim of this study was to evaluate optical coherence tomography (OCT) and intravascular ultrasound (IVUS) versus coronary angiography in the assessment of target lesion calcification and its effect on stent expansion.

IVUS is more sensitive than angiography in the detection of coronary artery calcium, but the relationship among IVUS, OCT, and angiography has not been studied.

Overall, 440 lesions (440 patients with stable angina) underwent OCT- and IVUS-guided stent implantation. Coronary calcification was evaluated using: 1) angiography; 2) IVUS (maximum calcium angle and the surface pattern); and 3) OCT (mean and maximum calcium angle, calcium length, and maximum calcium thickness).

Median patient age was 66 years, and 82.5% were men. Among 440 lesions, calcium was detected by angiography in 40.2%, IVUS in 82.7%, and OCT in 76.8%. The maximum calcium angle, maximum calcium thickness, and calcium length by OCT or IVUS increased in relation to the increasing severity of angiographically visible calcium. In 13.2% of lesions with IVUS-detected calcium, calcium was either not visible or was underestimated (>90° smaller maximum arc) by OCT mostly due to superficial OCT plaque attenuation. In 21.6% of lesions with IVUS calcium angle >180°, angiography did not detect any calcium; these lesions had thinner and shorter calcium deposits as assessed using OCT, and final minimum stent area was larger compared to those with angiographically visible calcium. In lesions with thinner calcium deposits by OCT, IVUS detected a smooth surface with reverberations whereas thick calcium deposits were associated with an irregular surface without reverberations.

Angiographic detection of target lesion coronary calcium (compared to intravascular imaging) has not changed in the past 2 decades, and angiographically invisible calcium (only detectable by IVUS or OCT) did not appear to inhibit stent expansion.