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circulation maintained in small anastomosing vessels when the main vessel is obstructed.
collateral circulationCardiology Blood flow that pursues a channel or system of vessels that is alternative to, or develops in substitution for, a major vascular pathway
Collateral circulation coronary artery
Grade 0 No flow in the collateral
Grade 1 Collateral is barely apparent; dye is present in at least 3 consecutive frames
Grade 2 Collateral is moderately opaque but present throughout at ≥ 75% of the cardiac cycle; there is antegrade motion of the dye rather than diffuse filling.
Grade 3 Collateral is well opacified and the column of dye is well defined–ie, > 0.5 mm in diameter, but < 0.7 mm wide over majority of length; collateral has clear antegrade dye motion
Grade 4 Collateral is well opacified, fills antegrade, and is very large; > 0.7 mm in diameter over entire length (Am Heart J 1999; 137:169)
col·lat·er·al cir·cu·la·tion(kŏ-lat'ĕr-ăl sĭr'kyū-lā'shŭn)
Circulation maintained in small anastomosing vessels when the main vessel is obstructed.