Impact of proximal cap ambiguity on the procedural techniques and outcomes of chronic total occlusion percutaneous coronary intervention: Insights from the PROGRESS-CTO Registry

Background: Proximal cap ambiguity is a key parameter in the global chronic total occlusion (CTO) percutaneous coronary intervention (PCI) crossing algorithm. Methods: We examined the baseline characteristics and procedural outcomes of 9718 CTO PCIs performed in 9498 patients at 41 US and non-US centers between 2012 and 2022. Results: Proximal cap ambiguity was present in 35% of CTO lesions. Patients whose lesions had proximal cap ambiguity were more likely to have had prior coronary artery bypass graft surgery (37% vs. 24%; p < 0.001). Lesions with proximal cap ambiguity were more complex with higher J-CTO score (3.1 ± 1.0 vs. 2.0 ± 1.2; p < 0.001) and lower technical (79% vs. 90%; p < 0.001) and procedural (77% vs. 89%; p < 0.001) success rates compared with nonambiguous CTO lesions. The incidence of major adverse cardiovascular events (MACE) was higher in cases with proximal cap ambiguity (2.5% vs. 1.7%; p < 0.001). The retrograde approach was more commonly used among cases with ambiguous proximal cap (50% vs. 21%; p < 0.001) and was more likely to be the final successful crossing strategy (29% vs. 13%; p < 0.001). The antegrade dissection and re-entry (ADR) “move-the-cap” techniques were also more common among cases with proximal cap ambiguity. Conclusions: Proximal cap ambiguity in CTO lesions is associated with higher utilization of the retrograde approach and ADR, lower technical and procedural success rates, and higher incidence of in-hospital MACE.