It is difficult to explain the presence of any MES in the MO.MA group. After all, there ought to be flow arrest once ‘protection’ is established. Perhaps movements of the occlusion balloon in the CCA and ECA can liberate small particles through microintimal damage? The other potential explanation is misalignment of the ECA balloon, which is mounted at a fixed distance from the end of the sheath.

Flow Reversal
The Parodi antiembolism system (PAES) (Arteria Medical Science, Inc., San Francisco, California) has been modified after Juan Parodi’s original design. The only device available that effects constant passive procedural flow reversal is the Gore NPS. The system achieves reversed flow by means of occluding the CCA and ECA with elastomeric balloons. The system is connected to the contralateral femoral vein via the Gore External Filter, creating an arteriovenous shunt. Therefore, blood passes from the contralateral cerebral circulation across the circle of Willis, down the ICA to be treated (by reversed flow), and into the low-pressure femoral vein (see Figure 2).

In a seven-centre, non-randomised prospective trial, Adami et al.¹³ treated 28 out of 30 patients using PAES. Flow reversal was not tolerated, presumably because of inadequacies of the circle of Willis and/or significant disease of the contralateral ICA in the remaining two patients. TCD monitoring in all patients demonstrated a complete absence of MES during the procedures (see Figure 3).

As yet there are no data available on the efficacy of the Gore NPS. However, a post-marketing study is planned in the US and Europe to assess procedural safety, namely the Embolic Protection with flow Reversal study.

Södersjukhuset’s Experience with Flow Reversal
At Södersjukhuset in Stockholm, CAS has been performed since late 2004. In common with most other centres worldwide, the CPD of choice has been filters. Our filters of choice have been the SpideRx/FX, because this system enables the operator to cross the lesion with his/her preferred wire. Our second CPD is the FilterWire EZ. When the Gore NPS became available, the decision was made within the team, comprising interventional radiologists and vascular surgeons, to trial the device in our routine clinical practice because we approved of the concept. We have utilised flow reversal in 12 cases, although one patient did not tolerate it. The remaining 11 patients tolerated the system well and had good outcomes from CAS. We are fortunate in having had access to the refined system and support from WL Gore, Scandinavia. Consequently, it would appear that, although modest, our experience is in fact one of the largest experiences of the modified system to date.

At first, this system appears cumbersome, but after a few cases this rapidly becomes irrelevant. We have found that the procedure time is comparable with filter-protected cases, and so far we have not had any adverse events. At our institution we do not have access to TCD and thus we have not been able to critically evaluate the system in a systematic way regarding MES.