Intravascular ultrasound–derived calcium score to predict stent underexpansion in moderately to severely calcified lesions

The original intravascular ultrasound (IVUS) calcium score in percutaneous coronary intervention (PCI) applies only to lesions with a maximum calcium angle > 270°, distinguishing it from the optical coherence tomography (OCT) calcium score. We aimed to investigate a new IVUS-derived calcium score to predict stent underexpansion in moderately to severely calcified lesions. We retrospectively analyzed 238 IVUS-guided PCI cases with moderate to severe calcification visible on angiography, including 136 cases with IVUS-guided PCI as a derivation cohort and 102 cases with both IVUS- and OCT-guided PCI as a validation cohort, excluding cases in which atherectomy was used. In the derivation cohort, IVUS-derived maximum calcium angle showed significant area under the curve (AUC) to predict stent underexpansion (< 70%) at the maximum superficial calcium site (cutoff value: 228°, AUC: 0.72). A multivariable linear regression model showed that maximum calcium angle of 225° (regression coefficient: -11.69; p = 0.023) and the presence of calcified nodule (regression coefficient: -4.913; p = 0.004) were associated with stent expansion. A new IVUS calcium score (0-4 points) was defined as 3 points for maximum calcium angle > 225°, and 1 point for presence of a calcified nodule. A cutoff of ≥ 3 showed a good AUC (0.751) and an excellent negative predictive value (0.963) to predict stent underexpansion. In the validation cohort, the incidence of stent underexpansion was 0%, 0%, 8.6%, and 33.3% in patients with the new IVUS calcium score of 0, 1, 3, and 4, respectively (p = 0.004). The new IVUS-derived calcium score can effectively predict stent expansion in moderately to severely calcified lesions.