COLLATERAL FLOW CHANGES THROUGH THE ANTERIOR COMMUNICATING ARTERY DURING CAROTID ENDARTERECTOMY

To evaluate early changes in collateral flow through the anterior comm unicating artery, 11 patients undergoing carotid endarterectomy were m onitored. All had angiographically demonstrated collateral flow toward s the hemisphere on the side of surgery. The middle cerebral artery ip silateral to the operated side and the contralateral anterior cerebral artery were simultaneously insonated with a transcranial Doppler inst rument equipped with dual transducers, and flow velocity values were o btained at specific surgical stages. Mean flow velocity in the contral ateral anterior cerebral artery's Al segment increased at clamp placem ent (p = 0.036), did not change during clamping, and decreased at clam p release (p = 0.004). The rise in velocity occurred within seconds of clamp placement in all patients with an increase, reaching the 10 cm/ s threshold within 1 min. No consistent increase was detected after 5 min. A decrease in pulsatility index, indicating a drop in resistance, was detected at clamp placement in the middle cerebral artery on the side of surgery (p = 0.012). The index did not change during clamping, but increased at clamp release (p = 0.002). Our findings indicate tha t significant changes in anterior communicating artery collateral flow occur during carotid endarterectomy, starting within seconds of carot id artery clamping. These changes are associated with arterial resista nce alterations in the territory of the middle cerebral artery on the endarterectomy side. Our observations should be useful to assess intra cranial early collateral flow changes in surgical and non-surgical set tings.