Bunny waveform sign

Bunny waveform sign refers to the biphasic morphology of the pulsed wave Doppler spectral waveform in the vertebral artery in early (occult/latent or partial) subclavian steal phenomenon (sometimes called a "presteal" state, before it progresses to frank flow reversal). There is a sharp deceleration of flow during peak systole due to a drop in pressure in the stenotic segment of the subclavian artery when flow is fastest . Different depictions differ as to whether the bunny is facing to the left  or right .