Predicting Successful Recanalization in Patients with Native Coronary Chronic Total Occlusion: The Busan CTO Score

Background: The optimal strategy to manage chronic total occlusion (CTO) remains unclear. The Japanese CTO multicenter registry (J-CTO) score is an established tool for predicting successful recanalization. However, it does not take into account nonangiographic predictors for final technique success. In the present study, we designed and tested a scoring model called the Busan single-center CTO registry (B-CTO) score combining clinical and angiographic characteristics to predict successful CTO recanalization in Korean patients. Methods: Prospectively enrolled CTO patients (n = 438) undergoing coronary intervention (1999-2015) were assessed. The B-CTO score comprises 6 independent predictors: age 60-74 years and lesion length ≥20 mm were assigned 1 point each, while age ≥75 years, female gender, lesion location in the right coronary artery, blunt stump, and bending >45° were assigned 2 points each. For each predictor, the points assigned were based on the associated odds ratio by multivariate analysis. The lesions were classified into 4 groups according to the summation of points scored to assess the probability of successful CTO recanalization: easy (score 0-1), intermediate (score 2-3), difficult (score 4-5), and very difficult (score ≥6). CTO opening was designated as the primary endpoint regardless of the interventional era or the skill of the operator. Results: The final success rate for B-CTO was 81.1%. The probability of successful recanalization for patient groups classified as easy (n = 64), intermediate (n = 148), difficult (n = 134), and very difficult (n = 92) was 95.3, 86.5, 79.1 and 65.2%, respectively (p for trend <0.001). When compared to the J-CTO, the B-CTO score demonstrated a significant improvement in discrimination as indicated by the area under the receiver-operator characteristic curve (AUC 0.083; 95% CI 0.025-0.141), with a positive integrated discrimination improvement of 0.042 and a net reclassification improvement of 56.0%. Conclusions: The B-CTO score has been designed and validated in Korean patients with native coronary CTO and is an improved tool for predicting successful recanalization. Wider application of the B-CTO score remains to be explored.