Table 1.

Angiographic Definitions of Collaterals Supplying Occluded Coronary Arteries.

Rentrop classification12	Developed for occluded and non-occluded arteries
0	no filling of collateral vessels
1	filling of collateral vessels without any epicardial filling of the target artery
2	partial epicardial filling by collateral vessels of the target artery
3	complete epicardial filling by collateral vessels of the target artery
Collateral connection grade11	In CTOs, Rentrop 3 is prevalent in 85% of lesions, CC grading provides an additional differentiation
CC0	no continuous connection
CC1	threadlike continuous connection
CC2	side branch–like connection (≥0.4mm)
CC3	>1mm diameter of direct connection (not included in the original description)