Stent Underexpansion Prediction Is Improved by Intravascular Ultrasound‐Based Distance‐Averaged Calcium Angles

BACKGROUND: Calcified coronary lesion, assessed by intravascular ultrasound (IVUS)-based maximum calcium angle, is an important predictor for stent underexpansion. AIMS: We aimed to determine whether the mean of all calcium angles measured within a specified distance from the maximum calcium site (distance-averaged) using IVUS was associated with stent underexpansion. METHODS: Patients undergoing IVUS-guided percutaneous coronary intervention (PCI) with drug-eluting stent implantation between 2016 and 2022 in a single tertiary center were retrospectively analyzed. Pre-PCI IVUS was used to assess the angles of calcified plaque every 1 mm; a total of 11 calcium angles were measured within 5 mm of the maximum calcium site. The endpoint was percent stent expansion, and stent underexpansion was defined as percent stent expansion < 70%. RESULTS: In the analysis of 87 stent underexpansions that occurred among 292 patients, distance-averaged calcium angles were significantly associated with stent underexpansion. Discrimination increased when using distance-averaged calcium angles instead of maximum calcium angle, with the area under the receiver operating characteristic curve (AUC) ranging from 0.75 (95% CI, 0.69-0.82) for 10 mm-averaged calcium angles to 0.77 (95% CI, 0.72-0.83) for 2 mm-averaged calcium angles (p < 0.05). Compared to 2 mm-averaged calcium angles, increasing measuring distance did not result in significant improvement in AUC. CONCLUSION: Distance-averaged calcium angles were associated with stent underexpansion. Compared with maximum calcium angle, distance-averaged calcium angles improved the prediction of stent underexpansion. Among these, 2 mm-averaged calcium angles may be a simpler, equally accurate approach to predicting stent underexpansion.