High diastolic flow velocities in severe internal carotid artery stenosis:A sign of increased surgical risk?

Purpose: We reviewed the history and preoperative investigations of patient s with early postoperative neurologic events after carotid thromboendartere ctomy in an attempt to identify risk factors for neurologic complications. Methods: Patients with neurologic events/complications (S group, n = 14 pat ients) were compared with an age- and disease-matched control group (C grou p, n = 42 patients) selected from the whole carotid thromboendarterectomy m aterial between 1987 and 1996. In this retrospective study, we re-evaluated the maximum systolic and end diastolic flow velocities within the internal carotid artery (ICA) using video recordings of preoperative Duplex ultraso und scan investigations. The flow velocity variables were compared with pre operative carotid angiography and intraoperative ICA stump pressure measure ment. Results: S-group did not differ from C-group concerning either cardiovascul ar risk factors or diseases, ipsilateral and contralateral angiographic gra de of ICA stenosis, or history of cerebral infarctions. Nevertheless, in co ntrast to control subjects, patients with early postoperative major stroke had higher end diastolic flow velocities and lower ICA stump pressures. Pat ients with postoperative minor stroke, transient ischemic attack, or amauro sis fugax did not differ significantly from the control subjects. Among pat ients with ICA stenosis of 75% or more, end diastolic flow velocities were correlated to the diastolic stump pressures. Conclusion: Diastolic flow velocities within severe internal carotid artery stenosis are dependent on the level of the collateral perfusion pressure d istally to the stenosis (ie, high values indicate a low internal carotid ar tery stump pressure), which seems to be a risk factor for early postoperati ve strokes.