Table 2:

The ASITN/SIR collateral-flow grading system to determine angiographic collateral grade on pretreatment angiography

ASTIN/SIR Collateral GradeDefinition
0No collaterals visible to the ischemic site
1Slow collaterals to the periphery of the ischemic site with persistence of some of the defect
2Rapid collaterals to the periphery of ischemic site with persistence of some of the defect and to only a portion of the ischemic territory
3Collaterals with slow but complete angiographic blood flow of the ischemic bed by the late venous phase
4Complete and rapid collateral blood flow to the vascular bed in the entire ischemic territory by retrograde perfusion
  • Note:—ASTIN/SIR indicates American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology.7