Color Doppler imaging evaluation of proximal vertebral artery stenosis.

OBJECTIVE: The sonographic diagnostic criteria for vertebral artery stenosis have not been fully investigated. The purpose of this study was to assess hemodynamic parameters at color Doppler imaging and to determine, with digital subtraction angiography as the reference standard, the optimal thresholds for evaluation of proximal vertebral artery stenosis. MATERIALS AND METHODS: Among 653 patients with symptoms of ischemia of the posterior circulation, 247 subjects with normal arteries or stenosis of the proximal vertebral artery confirmed with digital subtraction angiography were included in the study. Peak systolic velocity at the origin of the vertebral artery (PSV(origin)) and in intervertebral segments of the vertebral artery (PSV(IV)), end-diastolic velocity at the origin and in the intervertebral segments of the vertebral artery, and the diameter of the vascular lumen were measured. The cutoff values for the diagnosis of < 50%, 50-69%, and 70-99% stenosis were determined with receiver operating characteristics analysis. RESULTS: The optimal cutoff values of hemodynamic parameters in evaluation of stenosis of the proximal vertebral artery for < 50% stenosis were PSV(origin) >or= 85 cm/s, PSV(origin) / PSV(IV) >or= 1.3, and end-diastolic velocity at the origin >or= 27 cm/s; for 50-69% stenosis were PSV(origin) >or= 140 cm/s, PSV(origin) / PSV(IV) >or/= 2.1, and end-diastolic velocity at the origin >or= 35 cm/s; and for 70-99% stenosis were PSV(origin) >or= 210 cm/s, PSV(origin) / PSV(IV) >or= 4.0, and end-diastolic velocity at the origin >or= 50 cm/s. PSV(origin) was the most useful hemodynamic parameter, having accuracy of 94.5%, 96.2%, and 88.7% for the diagnosis of < 50%, 50-69%, and 70-99% stenosis. CONCLUSION: Color Doppler imaging is a reliable method for evaluation of vertebral artery stenosis. The results derived from this study can be used as a reference for establishing sonographic criteria for proximal vertebral artery stenosis.

The utility of using the bispectral index-Vista for detecting cross-clamping decline in cerebral blood flow velocity.

BACKGROUND: Patients undergoing carotid endarterectomy for extracranial internal carotid artery stenosis are at risk of cerebral ischemia/hypoperfusion. Criterion recommended by European and American committees to determine whether to place a shunt consisted of a decline in transcranial Doppler ultrasonography-measured middle cerebral artery blood flow velocity (MCBFV) to < 30% to 40% of intraoperative preclamp value. OBJECTIVE: To assess the discriminative power of the bispectral index (BIS)-Vista monitor for detecting a 40% decline in MCBFV with cross-clamping. METHODS: In 20 patients undergoing carotid endarterectomy under remifentanil/propofol anesthesia, BIS-Vista data, MCBFV, and pulsatility index from bilaterally mounted BIS-Vista and transcranial Doppler monitors were continuously recorded. RESULTS: Coefficient of determination revealed good correlation (r = 0.763) between ipsilateral BIS-Vista and MCBFV after cross-clamping. BIS-Vista exhibited a high discriminative power of 0.850 (95% confidence interval, 0.455-0.966) area under the receiver-operating characteristic curve in detecting an ipsilateral 40% MCBFV decline. Two-way analysis of variance (location by time) suggests that BIS-Vista exhibited a global decline; ie, both BIS-Vistas declined when 1 carotid on either side was clamped because there was no significant interhemispheric difference (P = .112) in mean BIS-Vista values over time. CONCLUSION: Although we demonstrated good correlation and high discriminative power of the BIS-Vista monitor in depicting a MCBFV decline that could serve as indicator of decline in cerebral activity, BIS-Vista cannot be considered a reliable indicator of cerebral ischemia/hypoperfusion that could replace transcranial Doppler monitoring to determine whether a shunt is to be placed.