Abstract
The effects of hematocrit (Ht) on the size of infarction and functional outcome of thrombotic internal carotid artery (ICA) occlusion with antegrade or retrograde collateral circuration were studied. According to the angiographic findings of the collaterals, the subjects were devided into the two groups, one the antegrade group (Group A : N=31), in whom the collateral blood flow was circulating in an antegrade manner through the circle of Willis, and the other the retrograde group (group R : N=36), in whom the collateral blood flow was circulating in a retrograde manner through the branches of external carotid artery and/or leptomeningeal anastomosis. The size of infarction was determined from CT on the chronic phase of infarction and calculated from following formula : Area of maximum low density/Area of maximum hemisphere on CT. Functional outcome was graded upon the ability of walking.
In Group A, there was no significant correlation between Ht and size of infarction (r=0.19) and no significant correlation between Ht at functional outcome. On the otherhand in Group R, a significant correlation existed between Ht and size of infarction (r=0.41), p<0.05), and functional outcome of high Ht (Ht≥45%) group was poorer than low Ht (Ht<45%) group.
The results of the present study suggest that Ht may give more important effects on the prognosis of ICA occlusion with retrograde collaterals than that with antegrade collaterals. In the retrograde collaterals, the blood flow has to go through the resistance vessels twice, while once in the antergrade collaterals. Moreover, the retrograde collaterals are generally longer in distance compared to the antegrade collaterals. Therefore, the flow velocity in the retrograde collaterals is likely to be slower than in the antegrade collaterals. The difference in flow velocity (shear rate) may contribute to the effects of Ht on the prognosis of ICA occlusion with retrograde collaterals.
