Development and validation of a predictive score for anterograde crossing of infrapopliteal chronic total occlusions: (The Infrapop-CTO Score)

Background: Patients with critical limb ischemia often have infrapopliteal (IP) chronic total occlusions (CTOs). While revascularization is indicated to prevent major amputation, anterograde crossing of these lesions can be challenging, with high failure rates.

Objective: To develop and validate a scoring system that can adequately predict successful anterograde crossing of infrapopliteal CTOs.

Methods and results: A total of 213 IP CTOs (147 successfully crossed with the anterograde approach vs. 66 where anterograde crossing failed) were included in the analysis. Backwards stepwise selection (p for retention <.05) was used to create a multivariable logistic regression model for the prediction of successful anterograde crossing using variables that were found to have a p < .1 in univariate analysis. The model was internally validated with bootstrapping and demonstrated excellent discriminatory ability (C-statistic 0.78 and Hosmer-Lemeshow p value = .61). A point score based on the beta-coefficient of the model variables was created, with one point assigned for presence of a noncentral (blunt) stump, one point for severe calcification at the entry site, and two points each for non-restenotic lesions or lesion length > 200 mm. The score was shown to have an excellent discriminatory ability for successful crossing, with low scores (0-2) associated with low failure rates (10%) and high scores associated with high failure rates (79%).

Conclusions: The Infrapop-CTO score can stratify the procedural complexity of IP CTOs based on the likelihood of successful anterograde crossing. This score may help to direct optimal approaches toward infrapopliteal revascularization of patients with critical limb ischemia.