The presence of collateral circulation has been shown to be associated with improved recanalization after thrombolysis and mechanical thrombectomy. However, with the advent of stent retrievers, it is hypothesized that improved recanalization can be achieved irrespective of collaterals. To test this, Liebeskind et al. retrospectively analyzed angiographic collateral grade prior to endovascular therapy in the SWIFT (SOLITAIRE™ FR With the Intention For Thrombectomy) study to ascertain the potential impact of collaterals on revascularization without symptomatic hemorrhage. They also sought to identify predictors of collateral grade in that study population.
They authors revealed a significant association between elevated blood glucose and systolic blood pressure at presentation and worse collaterals. In addition, the absence of prior HTN, a positive history for smoking, and high blood glucose were predictors of worse collaterals. Furthermore, low ASPECTS at baseline and at 24 hrs post-intervention were associated with worse collaterals.
The presence of collaterals was closely linked with improved reperfusion and revascularization without symptomatic hemorrhage, and overall better clinical outcome at defined by NIHSS at day 7 and mRS at day 90.
These data undermine the credibility of the SWIFT study results. You may recall that the SWIFT study compared the Solitaire device to the Merci retriever. The study concluded that the Solitaire device achieved substantially better angiographic, safety, and clinical outcomes than did the Merci Retrieval System. The current study by Liebeskind et al. reveals that collateral grade (partly driven by HTN, DM, and smoking) ultimately made a significant difference in outcome, irrespective of device used (although the authors did not discuss this point). The presence of collaterals was a confounding variable that was unadjusted for in the SWIFT trial. Perhaps the hype about the Solitaire device is unwarranted. It would be interesting to see the outcome of the SWIFT study after adjusting for the collateral grade.