A new optical coherence tomography-based calcium scoring system to predict stent underexpansion

Aims: This was a retrospective study to develop and validate an optical coherence tomography (OCT)-based calcium scoring system to predict stent underexpansion. Methods and results: A calcium score was developed using 128 patients with pre- and post-stent OCT (test cohort) and then validated in an external cohort of 133 patients. In the test cohort, a multivariable model showed that the independent predictors of stent expansion were maximum calcium angle per 180 degrees (regression coefficient: -7.43; p<0.01), maximum calcium thickness per 0.5 mm (-3.40; p=0.02), and calcium length per 5 mm (-2.32; p=0.01). A calcium score was then defined as 2 points for maximum angle >180 degrees, 1 point for maximum thickness >0.5 mm, and 1 point for length >5 mm. In the validation cohort, the lesions with calcium score of 0 to 3 had excellent stent expansion, whereas the lesions with a score of 4 had poor stent expansion (96% versus 78%, p<0.01). On multivariate analysis the calcium score was an independent predictor of stent underexpansion. Conclusions: An OCT-based calcium scoring system can help to identify lesions that would benefit from plaque modification prior to stent implantation. Lesions with calcium deposit with maximum angle >180 degrees, maximum thickness >0.5 mm, and length >5 mm may be at risk of stent underexpansion.