Vertebral Artery (VA) Waveform Patterns

Application Instructions:

a. Interruption of the systolic peak, alternating flow pattern (to-and-fro, bidirectional, oscillating) and fully reversed vertebral flow are associated with varying degrees of proximal subclavian artery stenosis (proximal to the origin of the vertebral artery), subclavian steal.

b. Normal velocities are generally 40-50 cm/sec.  Increased velocity >100 cm/sec, velocity ratio >2 pre to peak and/or PST are consistent with stenosis.

c. Slow acceleration to systolic peak indicates more proximal stenosis.

d. Absent forward flow signal throughout diastole (high resistance) is consistent with distal obstruction an possibly also with vertebral artery dissection.

e. Absence of flow with spectral Doppler in a visualized vertebral artery is consistent with occlusion; visualization of the vertebral vein also increases diagnostic confidence. 

f. Dominant vertebral: one may be larger than the other with velocity 20% higher or more.

Doppler Criteria for Common and External Carotid Arteries

• “Velocity Ratio” compares the focally elevated velocity to the normal velocity immediately proximal.

• Generally, only ≥50% diameter reduction is reported at the discretion of the interpreting physician, otherwise the presence of plaque is documented.