Impact of calcium burden, lesion preparation, and lithotripsy on stent underexpansion in severely calcified coronary lesions - a substudy of the BALI trial.

BACKGROUND: Stent underexpansion in severely calcified coronary lesions increases the risk of target vessel failure. Intravascular imaging (IVI) is recommended to improve results, yet IVI criteria for successful calcium modification remain unclear. AIMS: To identify optical coherence tomography (OCT) predictors of stent underexpansion in severely calcified coronary lesions based on pre-stent OCT imaging. METHODS: In the BALI trial, patients with severely calcified lesions were randomized to OCT-guided lesion preparation with vs without lithotripsy. Pre-stent OCT pullbacks were analyzed for calcium morphology, stenosis, and fractures. These findings were correlated with stent underexpansion (stent area ≤ 80% of reference) on spatially matched post-procedure OCT pullbacks. RESULTS: Stent underexpansion occurred in 33.9% of patients (56/165). At the frame level, embedded calcium >270° (odds ratio (OR) 2.8, p = 0.02), nodular calcium >90° (OR 4.1, p < 0.001), and pre-stent area stenosis ≥20% (OR 4.3, p < 0.001) were associated with stent underexpansion. In frames with calcium >270°, one, two, or more fractures was associated with an increase in stent area of 0.2, 0.6, and 0.7 mm2 (p = 0.1, p = 0.002, p = 0.01), respectively. Randomization to lithotripsy led to a higher frequency of fractures (OR 1.8, p = 0.004) and improved stent expansion at the site of maximal calcification (relative risk 0.50, p = 0.01). CONCLUSIONS: Luminal gain and multiple fractures in severely calcified lesions before stent implantation predict stent expansion. Lithotripsy increases the frequency of fractures and improves stent expansion compared to conventional preparation alone.