A Revised Optical Coherence Tomography-Derived Calcium Score to Predict Stent Underexpansion in Severely Calcified Lesions

Abstract

Background: Severe calcification is the morphology most strongly associated with stent underexpansion.

Objectives: The aim of this study was to revise an optical coherence tomography (OCT)-derived calcium score to predict stent underexpansion in severely calcified lesions (angle >270°) using a point-based system.

Methods: A retrospective observational study was conducted in which 250 de novo lesions undergoing OCT-guided stenting, with angiographically visible calcium and optical coherence tomographic maximum superficial calcium angle >270°, not subjected to atherectomy or specialty balloon treatment before stent implantation, were randomly divided into derivation (n = 167) and validation (n = 83) cohorts. The endpoint was stent expansion (minimum stent area/average of reference luminal area) at the maximum calcium deposition site, and stent expansion <70% was considered underexpansion.

Results: Stent underexpansion was present in 19.6% of lesions (49 of 250). In the multivariable linear regression model, the morphologic characteristics associated with stent expansion in the derivation cohort were: 1) calcium >270° with a length longer than 3 mm (regression coefficient = -10.3; 95% CI: -17.8 to -2.8; P = 0.007); 2) calcium angle of 360° (regression coefficient = -15.5; 95% CI: -25.2 to -5.8; P = 0.002); and 3) minimum calcium thickness >0.30 mm (regression coefficient = -12.4; 95% CI: -19.1 to -5.6; P = 0.0004). In the validation cohort, the calcium score (range: 0-3) was significantly correlated with stent expansion (regression coefficient = -9.1; 95% CI: -12.6 to -6.1; P < 0.0001).

Conclusions: This revised OCT-derived calcium score can serve as a reliable tool for identifying severely calcified lesions at risk for stent underexpansion.

Keywords: optical coherence tomography; percutaneous coronary intervention; severe calcified plaque; stent(s).