EuroCTO: A Simple Scoring System to Predict Technical Success when Performing CTO PCI Derivation and Validation of a Chronic Total Coronary Occlusion Intervention Procedural Success Score From the 20,000-Patient EuroCTO Registry: The EuroCTO (CASTLE) Score

A study by Zsolt Szijgyarto and his colleagues published in JACC: Cardiovascular Interventions has derived the EuroCTO (CASTLE) from the largest database of CTO cases to date and offers a useful tool for predicting procedural outcomes. The investigators stated that previous CABG, age over 70 years, a blunt stump, severe tortuosity, length of the occlusion, and the extent of calcification were strongly associated with unsuccessful CTO-PCI.

It is known that chronic total occlusions (CTOs) are present in approximately one-fifth of patients undergoing coronary angiography. In the past, these lesions have often been treated either with medical therapy or coronary artery bypass grafting (CABG) in suitable candidates due to their complexity and low interventional success rates. Percutaneous coronary intervention (PCI) of CTOs has become more widely accepted in the last decade, with increasing rates of success rates in relation with operator experience, guidewire technology, and microcatheter sophistication. Despite these improvements, procedural success rates remain lower than those achieved with non-occlusive lesions. A simple and accurate scoring tool to grade the difficulty of cases would be valuable for appropriate case selection and planning. Attempts have been made to classify procedures according to their likelihood of success based on patient, lesion, and procedural features. Predictors of technical success or failure have been derived from datasets of modest size. A robust scoring tool could facilitate case selection and inform decision making. In light of this, the study investigators aimed to establish a contemporary scoring system to predict the outcome of chronic total occlusion coronary angioplasty. The study analyzed data from the EuroCTO registry. This prospective database was set up in 2008 and includes >20,000 cases submitted by CTO expert operators (>50 cases/year). Derivation (n ¼ 14,882) and validation (n ¼ 5,745) datasets were created to develop a risk score for predicting technical failure.

There were a total of 14,882 patients in the derivation dataset (with 2,356 [15.5%] failures) and a total of 5,745 in the validation dataset (with 703 [12.2%] failures). Approximately 20.2% of cases were performed retrogradely, and dissection re-entry was done in a total of 9.3% of cases.  Szijgyarto and his colleagues identified 6 predictors of technical failure, collectively forming the CASTLE score (Coronary artery bypass grafting history, Age (≥70 years), stump anatomy (blunt or invisible), tortuosity degree (severe or unseen), length of occlusion (≥20 mm), and extent of calcification (severe). When each parameter was assigned a value of 1, technical failure was seen to increase from 8% with a CASTLE score of 0 to 1, to 35% with a score ≥4.  Moreover, the area under the curve (AUC) was similar in both the derivation (AUC: 0.66) and validation (AUC: 0.68) datasets.

Summarizing the results of his study, Dr. Rajiv Rampat remarked, “We examined data from the Euro-CTO Registry of 20,000 prospectively entered cases from dedicated CTO operators and created a simple integer scoring system to predict a technical outcome. The following factors were found to be of greatest importance—coronary artery bypass grafting history, age, stump anatomy, tortuosity degree, length of occlusion, and extent of calcification. Technical failure rates range from 8% (CASTLE score 0 to 1) to 35% (CASTLE score ≥4).” Enlisting the benefits of the scoring system in his study, primary investigator Dr. Zsolt Szijgyarto stated, “We present a simple scoring system to predict technical success when performing CTO PCI. Despite technical advances, CTO PCI remains one of the most difficult areas of interventional cardiology and the one most likely to fail. Therefore, being able to predict in advance the likelihood of success will help cardiologists choose wisely, in a number of important ways. First, it will help guide interventionalists during their learning phase as CTO operators in terms of case selection. Second, it will aid heart team discussions regarding the likelihood of complete revascularization with PCI or CABG. Third, it will aid comprehensive informed consent for patients regarding the likelihood of CTO PCI success.” As the investigators believe that the lack of external validation is a limiting factor in their analysis, they acknowledge that the predictive ability of our model needs to be validated in future studies.