IVUS findings predicting the indication for intravascular lithotripsy in PCI

Background In Japan, the indication for intravascular lithotripsy (IVL) in PCI is an OCT or IVUS calcium score ≥3, but there is a large difference between the two. There are many cases in which the use of IVL is considered, but IVUS calcium score is not ≥3, resulting in IVL inappropriate. However, even in such cases, the OCT calcium score is often ≥3. Purpose The purpose of this study is to investigate IVUS findings to predict OCT calcium score ≥3, or angiographic indication for IVL. Methods From consecutive 2908 PCIs in our institution between March 2015 and December 2022, we retrospectively analyzed 110 PCIs with angiographically confirmed calcification and available pre-OCT/OFDI and pre-and post-IVUS data which were performed simultaneously in the culprit lesions. We investigated IVUS findings to predict OCT calcium score ≥3 which is considered to the indication for IVL, or angiographic indication for IVL defined as sites by a) angiography, with fluoroscopic radio-opacities noted without cardiac motion prior to contrast injection involving both sides of the arterial wall in at least one location and total length of calcium of at least 15mm and extending partially into the target lesion, OR by b) IVUS or OCT, with presence of ≥270 degrees of calcium on at least 1 cross section. Results Of 110 lesions, 106 lesions had IVUS calcium score <3. From these 106 lesions, 74 lesions had OCT calcium score ≥3 (70%) and 76 met angiographic criteria for IVL (69%). IVUS-derived calcium angle(cutoff value of 227 degree, AUC 0.95), IVUS-derived calcium length (cutoff value of 12.3 mm, AUC 0.81), IVUS-derived calcium length with a calcium angle >180 degree (cutoff value of 2.9 mm, AUC 0.92), and IVUS-derived calcium length with a calcium angle of >270 degree (cutoff value of 0.9 mm, AUC 0.86) showed excellent AUCs in ROC analyses to predict OCT calcium score ≥3. IVUS-derived vessel diameter at the maximum calcium site and IVUS-derived calcified nodule could not predict it. IVUS-derived calcium angle (cutoff value of 240 degrees, AUC 0.94), IVUS-derived calcium length (cutoff value of 16.0mm,AUC 0.78), and IVUS-derived calcium length with calcium angle of >180 degrees (cutoff value of 2.5mm,AUC 0.91) showed significant AUCs in ROC analyses to investigate the association with angiographic criteria. IVUS-derived vessel diameter at the maximum calcium site and IVUS-derived calcified nodule did not. Conclusions It may be possible to determine the indication for IVL based solely on IVUS-derived calcium angle or length, rather than IVUS calcium score.