CL Score (CTO Lesion Complexity) Calculator

CL Score (CTO Lesion Complexity): Explanation and Clinical Context The CL Score (CTO Lesion Complexity Score) is an angiographic grading system used to predict the procedural success rate of percutaneous coronary intervention (PCI) in chronic total occlusion (CTO) lesions. It is derived from the validated J-CTO score, first introduced by Morino et al. in 2011, and evaluates five anatomical features that influence the difficulty of guidewire crossing and procedural completion. Each variable contributes one point if present: blunt stump, calcification, severe tortuosity (>45° bending), occlusion length ≥20 mm, and prior failed CTO attempt.

The total score ranges from 0 to 5, with higher scores indicating more complex lesions and lower success rates. Based on validation data, procedural success was approximately 88% for easy (score 0), 67% for intermediate (score 1), 42% for difficult (score 2), and 18% for very difficult (score ≥3). This tool helps interventional cardiologists assess case complexity, estimate procedure duration, anticipate the need for specialized equipment or retrograde approach, and counsel patients regarding procedural risks and expectations.