Prediction of the Technical Success of Endovascular Therapy in Patients with Critical Limb Threatening Ischaemia Using the Global Limb Anatomical Staging System

Objective: This study aimed to determine the clinical impact of the Global Limb Anatomical Staging System (GLASS) and develop a model to determine the grade of difficulty for target artery path (TAP) using GLASS stage.Methods: This was a single centre retrospective study. Endovascular treatment (EVT) was performed for 400 lesions in 257 patients with critical limb threatening ischaemia (CLTI) between April 2009 and March 2018. All lesions were divided into three groups (GLASS I, II, and III), which were compared in terms of patient characteristics, lesion characteristics, technical success, and procedural complications. All observations were then randomly assigned to the derivation set or validation set at a ratio of 2:1 (derivation set: 166 patients; validation set: 91 patients). Predictors of technical success for TAP were identified by multivariable analysis. Each predictor was assigned a score based on its regression coefficient, and the total score was calculated. This value was used to categorise all lesions into the following four groups: low (score 0), intermediate (score 1), difficult (score 2), and very difficult (score >= 3).Results: No significant differences in patient characteristics were observed between the three GLASS groups. In GLASS III group, anatomic/limb severity and procedural complications were observed frequently, and the technical success rate was lower than that in the other groups. Through multivariable analysis, absence of pedal modifier (P)0 or P1, GLASS III, total occlusion, and severe calcification predicted technical failure. The four groups stratified according to GLASS score demonstrated stepwise and highly reproducible difference in the probability of technical success for TAR. The area under the receiver operating characteristic (ROC) curve was 0.95 in the development group and 0.93 in the validation sample.Conclusion: In GLASS III, anatomic/limb severity was more complex and procedural complications were more frequent. The GLASS scoring system reliably predicts the technical success of de novo TAP in patients with CLTI.