Diogo C. Haussen, MD

 De Vries J, Boogaarts J, Van Norden A, Wakhloo AK. New Generation of Flow Diverter (Surpass) for Unruptured Intracranial AneurysmsA Prospective Single-Center Study in 37 Patients. Stroke. 2013

Flow-diverting stents (FDS) became recently available as a treatment alternative for large and/or wide necked cerebral aneurysms. These devices have relative higher metal surface area coverage, reaching 30-35%. The low stent porosity bridges the aneurysm neck and deflects the flow that would typically fill the aneurysm back into the parent arterial lumen. This generates flow stagnation inside of the aneurysmal sac, and consequently promotes intraaneurysmal thrombosis. The stent struts endothelialize after a few weeks and “reconstruct” the vessel wall while side branches and penetrators remain remarkably patent. Currently, the only approved FDS in the US is the PipelineTM, and substantial literature has accrued over the past years regarding the use of this device. Although promising, not uncommon complications may occur (mostly thromboembolic and hemorrhagic – related to required double antiplatelet regimen). Some series report very low complication rates, however others describe that almost 1 in 10 patients experience significant morbidity or mortality.

De Vries et al. report their initial experience with a new FDS (SurpassTM) in 37 patients harboring unruptured aneurysms. A main theoretical advantage of this device resides on the fact that the implant maintains a uniform pore-density across the aneurysm neck unaffected by parent artery diameter – stents with larger width are built with more wires. Conversely, PipelineTM encompasses the same number of wires independent of the stent diameter. Weather this may result in better occlusion rates is unknown. The use of a mean 1.0 stent per patient is relatively low while their 6 months total obliteration rates are relatively similar compared to published PipelineTM series. Another attractive SurpassTM feature resides on the addition of platinum wires for improved visibility.

The effective and safe delivery of the PipelineTM stent demands sophisticated technique, which makes the reader wonder how easily manageable SurpassTM may be. Moreover, the Pipeline is not resheathable in case of an improper partial unsheathing (implant needs to be retracted and discarded); it is unclear whether the SurpassTM is resheathable as per this report. The community certainly welcomes the successful initial SurpassTM experience and enthusiastically awaits for further data.