Introduction/purpose The use of Stent-Retrievers in endovascular stroke therapy has recently been proven to improve patient outcomes. As an interventionist, our goal is to achieve TICI 2b-3 flow with minimal passes, within a short procedure time, while minimizing vessel trauma and distal or collateral embolization. Because we encounter a range of occlusions, from fresh erythrocyte-rich clot to older, tougher fibrin-rich clot with a variety of anatomical challenges, it is important to select the technique with the best odds of success. Observation of clot-device interaction in vitro using clinically representative clot analogs is a useful tool for the evaluation of procedural efficacy. We believe this tool, in combination with clinical observation, can help us improve techniques for clinical success.

Materials and methods We performed a retrospective review of cases performed at Karolinska University Hospital from October 2013 to June 2014. In vitro testing was carried out to better characterize clot-device interactions with a range of clot types. We combined the learning from the bench evaluations with our case experience to evaluate different techniques for various clinical scenarios.

Results Observations of clot/device interaction in vitro show that clots may experience high shear forces as they are drawn into catheters. The force magnitude depends on the mismatch between clot and catheter diameter. During testing, the stresses  on the clot were shown to manifest in different ways during retrieval. For example mature, fibrin rich clots were less likely to readily deform to enter the lumen of an intermediate catheter, which could lead to retrieval difficulties. Fresher less organized clots faced high shear forces, with more observed fragmentation, which may present a greater embolization risk. Such risks have implications for technique selection.

In our case series we performed 70% of cases under flow arrest with a balloon guide, and 30% were completed without flow arrest. In half of the cases using a balloon guide, an intermediate catheter was also used. TICI 2b-3 flow was achieved in 100% of cases, with 74% attaining TICI 3. 87% of cases were completed with 1–2 passes. Good outcomes (mRS 0–2) were achieved in 88% of the cases using a balloon guide, and in none of the cases without a balloon guide. Overall in the series, 61% of patients had good outcomes at 90 days.

Conclusion Our data indicate that thrombectomy with a stent-retriever and balloon guide system provides the best opportunity for good outcomes. Because of the risks of shearing off part or all of a clot when aspirating an oversized thrombus into an intermediate catheter and further retrieving against the flow in the internal carotid, our strategy is to use intermediate catheters in conjunction with a balloon guide whenever possible to achieve flow-arrest. We did not have a large enough sample size to draw conclusions about the impact of technique on the number of passes. Further evaluation of how to optimize techniques in different occlusion scenarios is needed as clinicians strive to improve clinical outcomes.

Disclosures T. Andersson: 2; C; Neuravi, Stryker, Covidien, J&J Codman, Rapid Medical.