Methods A patient undergoing transfemoral CAS with flowreversal through a Walrus BGC was monitored with a rTCD device (Figure 1 ). Results Red color at the depth of the ICA terminus indicates forward flow (Figure 1 ). Prior to crossing the plaque for placement of a distal filter and/or angioplasty, we inflate the BGC and open the three-way stopcock, allowing back bleed. At this moment, the rTCD shows a change in blood flow direction, indicated as change from red to blue (Figure 1 ), which

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... occurs due to a passive pressure gradient between the intracranial compartment and the atmospheric pressure. Then, the filter is placed with reduced risk of displacing plaque fragments, and angioplasty and stenting are performed with dual-layer of protection. Conclusions This technique may confer greater safety CAS with flow-arrest or without proximal protection. Though in this case rTCD was used for proof of concept, it can be also employed as a embolic monitoring tool during carotid artery procedures.