ANTERIOR COMMUNICATING ARTERY COLLATERAL FLOW PROTECTION AGAINST ISCHEMIC CHANGE DURING CAROTID ENDARTERECTOMY

The purpose of this study was to determine whether preoperative angiog raphic patterns of collateral cerebral blood flow correlate with prote ction against intraoperative electroencephalographic (EEG) evidence of cerebral ischemia caused by carotid artery cross-clamping during caro tid endarterectomy. Previous studies have shown that contralateral car otid artery occlusion and intracranial stenoses are associated with ce rebral ischemia during carotid endarterectomy; however, the angiograph ic collateral flow patterns associated with cerebral ischemia have not been identified. This paper reports a retrospective study of 67 patie nts who underwent two- to four-vessel cerebral angiography followed by carotid endarterectomy with 16-channel EEG monitoring. The angiograms were reviewed for extracranial occlusive disease and collateral flow patterns, and the EEG recordings were analyzed for ischemic changes du ring carotid artery cross-clamping. Statistical analysis was by Fisher 's exact test. Cross-filling of the anterior and middle cerebral arter ies from the contralateral carotid artery through the anterior communi cating artery correlated with a decreased incidence of EEG ischemic ch anges. Only 21% of patients with this collateral flow pattern showed i schemic changes compared to 50% of patients without this pattern (p < 0.03). Three angiographic findings occurring in combination on the sid e contralateral to surgery correlated with EEG ischemia: 1) occlusion of the contralateral internal carotid artery (five of seven or 71%, p < 0.03); 2) collateral flow from the external carotid circulation to t he internal carotid circulation via the ophthalmic artery; and 3) coll ateral flow from the posterior circulation to the contralateral anteri or circulation via the posterior communicating artery. The data presen ted here corroborate the correlation between contralateral carotid art ery occlusion and cerebral ischemia during carotid endarterectomy. The y also demonstrate that cross-filling of the anterior and middle cereb ral arteries by the contralateral carotid artery protects against such ischemia. This collateral flow may serve as an indicator of tolerance to carotid artery cross-clamping.