Table 2. Lesion characteristic among different collateral grading.

	Werner’s CC grading				Rentrop grading
	Grade 2 (n = 686)	Grade 0–1 (n = 1766)	P-value		Grade 3 (n = 1145)	Grade 0–2 (n = 1307)	P-value
Data are presented as means ± SD or n (%). CC: collateral circulation; CTO: chronic total occlusion; PCI: percutaneous coronary intervention.
Target vessel			< 0.001				0.023
Left main artery	1 (0.1%)	3 (0.2%)			3 (0.3%)	1 (0.1%)
Left anterior descending	249 (36.1%)	697 (38.9%)			448 (39.1%)	483 (37.0%)
Left circumflex artery	55 (8.0%)	308 (17.2%)			143 (12.5%)	217 (16.6%)
Right coronary artery	384 (55.7%)	773 (43.8%)			551 (48.1%)	606 (46.4%)
Reference vessel diameter, mm	3.1 ± 0.4	2.9 ± 0.4	< 0.001		3.0 ± 0.4	2.9 ± 0.4	< 0.001
CTO length, mm	18.4 ± 11.4	17.3 ± 12.6	0.029		16.5 ± 11.0	18.5 ± 13.2	< 0.001
Blunt stump	292 (42.6%)	722 (40.9%)	0.47		451 (39.4%)	563 (43.1%)	0.07
Moderate or severe calcification	98 (14.3%)	224 (14.7%)	0.29		140 (12.2%)	182 (13.9%)	0.23
Moderate or severe tortuosity	336 (49.0%)	737 (41.7%)	0.001		507 (44.3%)	566 (43.3%)	0.65
In-stent	54 (7.9%)	148 (8.4%)	0.74		68 (5.9%)	134 (10.3%)	< 0.001
Retry PCI	21 (3.1%)	59 (3.3%)	0.80		40 (3.5%)	40 (3.1%)	0.57
J-CTO score	1.5 ± 1.0	1.4 ± 1.0	< 0.001		1.4 ± 1.0	1.4 ± 1.0	0.10
PROGRESS score	0.6 ± 0.6	1.2 ± 0.9	< 0.001		0.8 ± 0.8	1.2 ± 0.9	< 0.001
SYNTAX score	18.0 ± 7.8	19.4 ± 8.4	< 0.001		19.8 ± 8.1	18.3 ± 8.3	< 0.001
PCI acute result			0.18				0.25
Optimal success	389 (56.7%)	1073 (60.8%)			699 (61.0%)	763 (58.4%)
Sub-optimal success	107 (15.6%)	247 (14.0%)			152 (13.3%)	202 (15.5%)
Failure	190 (27.7%)	446 (25.3%)			294 (25.7%)	342 (26.2%)