The collateral score grades distal arteries filling with a 4-point scale with (+) 0 constituting absent collaterals (0% filling of the occluded 8 territory), (+) 1for poor collaterals (>0% and ≤50% filling of the occluded territory), (+) 2 for moderate collaterals (>50% and <100% filling of the occluded territory), and (+) 3 for good collaterals (100% filling of the occluded territory).