Objective To investigate whether treatment of lesions of greater complexity is now undertaken and to assess the rates of procedural success per class of lesion complexity.

Design Observational study.

Setting Despite impressive progress in treatment strategies and equipment, the success rate of percutaneous coronary intervention for chronic total occlusion (CTO) has remained relatively stable.

Participants 483 patients consecutively treated with CTO from 2003 to 2012.

Main outcome measures The Multicenter CTO Registry of Japan (J-CTO) score was used to classify lesion complexity. The study population was subdivided into an early (period 1, n=288) and a late (period 2, n=195) period according to the routine implementation of novel techniques and advanced equipment.

Results Period 2 was marked by more ‘difficult’ and ‘very difficult’ lesions (J-CTO grades 2 and 3) being attempted, with procedural success increasing from 68.4% to 88.1% (p<0.001) and from 42.0% to 78.9% (p<0.001), respectively. ‘Easy’ and ‘intermediate’ lesions (J-CTO grades 0 and 1) were less common, but with similarly high success rates (89.1% vs 96.6% (p=0.45) for easy, and 86.3% vs 86.1% (p=0.99) for intermediate). Period 2 was characterised by a trend for more successful procedures overall (by 6.1%, p=0.09). Procedural complications were similarly low in both periods. J-CTO score and technical era were identified as independent correlates of success in the total population by logistic regression analysis.

Conclusions Advanced CTO techniques and equipment have resulted in an increase in the successful treatment of highly complex lesions. Total success rate did not substantially improve, as it was counterbalanced by the increased rate at which complex lesions were attempted.