Figure 1 Color Doppler ultrasound images and spectral waveform of the right vertebral artery showing bidirectional flow indicative of partial subclavian steal syndrome(A) Spectral Doppler waveform from the proximal right vertebral artery (RVA) obtained after a reactive handgrip maneuver demonstrates characteristic mid-systolic deceleration with alternating antegrade diastolic flow (above baseline) and retrograde systolic flow (below baseline), diagnostic of type 2 (intermittent/partial) subclavian steal physiology; note the preserved end-diastolic velocity. (B) Longitudinal color Doppler ultrasound image of the RVA in the V2 (cervical foraminal) segment shows bidirectional flow with red signal indicating flow toward the transducer (antegrade) and blue signal indicating flow away (retrograde), confirming hemodynamic instability provoked by subclavian/brachiocephalic pathology. RVA – right vertebral artery.