Figure 1.

Representative imaging of collaterals defined by Werner’s CC grading system and Rentrop grading system.

(A): Rentrop grade 0: no contrast filling of any collateral channel; (B): Rentrop grade 1: filling of collaterals without epicardial filling of the CTO artery (arrow); (C): Rentrop grade 2: partial filling of the epicardial vessel of the CTO artery (arrows); (D): Rentrop grade 3: complete epicardial filling of the CTO artery (arrows); (E): Werner’s CC grade 0: no visible connection between donor and recipient artery; (F): Werner’s CC grade 1: thread-like connection (arrow); and (G): Werner’s CC grade 2: continued side branch-like connection (arrows). CC: collateral circulation; CTO: chronic total occlusion.