To evaluate the correlation between the degree of subclavian artery (SA) stenosis with vertebral artery (VA) stenosis and the type of subclavian artery steal (SAS) by color Doppler ultrasonography (CDU).

A total of 503 patients with SA stenosis≥ 50% or occlusion with varying degrees of VA stenosis were consecutively enrolled from January 2013 to October 2017. All patients underwent CDU screening and confirmed by CT angiography (CTA) or digital subtraction angiography (DSA). According to the flow waveform of the VA, SAS was divided into three types: I (latent type), II (partial type), and III (complete type). Based on the degree of SA stenosis, the patients were divided into two groups: patients with SA stenosis ≥ 50% to<70% (n=254) and those with SA stenosis ≥ 70% (n=249). Based on the degree of VA stenosis, the patients were also divided into two groups: patients with VA stenosis ≥ 50% to<70% (n=391) and those with VA stenosis ≥ 70% (n=112). The correlation between the degree of SA stenosis with VA stenosis and the type of SAS was analyzed.

Among all 503 patients, type I SAS was the most common type, accounting for 50.3% (253/503), while types II and III accounted for 18.9% (95/503) and 26.0% (131/503), respectively; the percentage of patients with no SAS was 4.8% (24/503). There was a significant difference in the distribution of SAS types between patients with SA stenosis ≥ 50% to<70% and patients with SA stenosis ≥ 70% (P<0.01), with type I SAS being the most common type in patients with SA stenosis ≥ 50% to<70% (90.6%, 230/254) and type III being the predominant type in patients with SA stenosis ≥ 70%. In patients with SA stenosis ≥ 50% to<70%, there was no significant difference in the distribution of SAS types between patients with VA stenosis ≥ 50% to<70% and patients with VA stenosis ≥ 70% (P=0.184), with type I being the predominant SSA type in both groups. In patients with SA stenosis ≥ 70%, there was a significant difference in the distribution of SAS types between patients with VA stenosis ≥ 50% to<70% and patients with VA stenosis ≥ 70% (P<0.001); the percentage of patients with type III SAS was significantly higher in patients with VA stenosis≥50% to<70% than in patients with VA stenosis ≥70% (63.0% vs 2 5.0%, P<0.001), while he percentage of patients with type I SAS was significantly lower in patients with VA stenosis ≥50% to<70% than in patients with VA stenosis ≥ 70%.

The presence of VA stenosis ≥ 70% in patients with SA stenosis ≥70% can alter the distribution of SAS types. In patients with SA stenosis with different degrees of VA stenosis, there may be inconsistency between the degree of SA stenosis and the classification of SAS, which should be paid attention to in clinical ultrasound evaluation.