The vertebral artery typically presents what type of resistance waveform on duplex Doppler examination?

• A. High
• B. Low
• C. Moderate
• D. No flow

Answer: (B)

In duplex Doppler, the waveform reflects the downstream impedance of the vascular bed. The brain’s circulation is characteristically low resistance because autoregulation maintains relatively continuous flow, leading to forward flow throughout diastole. The vertebral arteries, as part of the posterior cerebral circulation, share this pattern. So you’d expect a low-resistance waveform with forward flow during diastole and a relatively broad systolic peak. If diastolic flow were markedly reduced or reversed, that would raise suspicion for proximal stenosis, subclavian steal, or other downstream resistance issues, not the normal vertebral pattern.