To compare the difference of waveform between intracranial and extracranialsegment of vertebral artery as well as hemodynamic parameters in patientswith subclavian steal syndrome and explore its relativity with clinical symptoms.

Between May 2015 and August 2014, 213 patients with moderate (50%-69%) orsevere stenosis or occlusive lesions detected by vascular ultrasound and CTA or DSA imaging were enrolled in this study. The blood flow waveform examined by color duplex flow imaging (CDFI) and transcranial Doppler (TCD) or transcranial color coded Doppler (TCCD) in extracranialand intracranial artery segment were comparisoned. According to the classical stages (stageⅠ: occult steal; stageⅡ: partial steal; stage Ⅲ: complete steal), the hemodymics paremeter such as peak systolic velocity (PSV) and end diastolic velocity (EDV) of intracranial and extracranial artery were analyzed and compared in patients with same degree of steal syndrome.

Among those 213 patients, there were 190 cases (89.2%, 190/213) with same degree of steal in intracranial and extracranial VA segments, including 52 cases (27.4%, 52/190) of phaseⅠsteal, 82 cases (43.2%, 82/190) of phaseⅡsteal and 56 cases (29.5%, 56/190) of phase Ⅲ steal. The analysis of the differences of blood velocities between the intracranial and extracranial VA in 190 patients with same stages of steal demonstrated that in patients with phaseⅡand phase Ⅲ steal, the PSVs and EDVs of intracranial segment were greater than those of the extracranial segment (P<0.05). There was no significant difference in patients with phaseⅠsteal (P>0.05). The incidence of clinical symptom was relatively higher in patients with phaseⅡstealthan those in patients with phaseⅠand Ⅲ steal with no statistical difference (P>0.05) in intracranial or extracranial segment. Among those patients with inconsistent degree of steal, the incidence of relevant symptom rates inhanced (39.1%>25.8%).

When there is stenosis of subclavian artery, the blood spectrum of VA reflects a relatively same degree of steal of both intracranial and extracranial VA. However, the blood velocity is obviously higher in intracranial VA comparing to extracranial VA in patients with phaseⅡand phase Ⅲ steal. The incidence of clinical symptom was relatively higher in patients with phaseⅡsteal than those in patients with phaseⅠand Ⅲ steal.