Volume flow rate evaluation in patients with obstructive arteriosclerotic disease.

This study was performed to quantify the volumetric impact of extracranial arteriosclerotic lesions. We investigated patients with different degrees of carotid stenosis as defined by conventional velocity-based duplex criteria and different patterns of collateralization. We studied the volume flow rate (color duplex M-mode device) in 37 patients with symmetrical internal carotid artery (ICA) plaques (<50% stenosis) and compared these data to 43 patients with a unilateral 50-74% stenosis, 75-99% stenosis (n = 73) and occlusion of the ICA (n = 37). A 75-99% stenosis caused an ipsilateral flow reduction of 36% with a wide interindividual variability, and an occlusion of 51%. Collateralization via the ophthalmic artery only caused a nonsignificant ipsilateral volume flow increase, whereas the contralateral volume flow was significantly higher in patients with a patent anterior communicating artery. The increase was more pronounced in patients with an occluded vessel. Our data demonstrate a wide diversity of the hemodynamic impact of carotid stenosis as defined by 'classical' Doppler criteria. Collateral flow reflects a dynamic quantitative process.