BackgroundBalloon guide catheters (BGCs) are used to prevent distal emboli during endovascular treatment for acute ischemic stroke. Although literature reports benefit of BGC, these are not universally used, and randomized head‐to‐head comparisons are lacking. This study compared functional, safety, and technical outcomes between patients treated with non‐BGC and with BGC during endovascular treatment in a nationwide prospective multicenter registry.MethodsPatients from the MR CLEAN (Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands) Registry, 2014 to 2018), who underwent endovascular treatment with a non‐BGC or BGC, were included. Primary outcome was the modified Rankin Scale score at 90 days, and secondary outcomes included procedure time and first‐attempt successful reperfusion (extended Thrombolysis in Cerebral Infarction ≥2C). Treatment‐effect modification and subgroups were analyzed according to first‐line thrombectomy technique and different sizes of non‐BGC.ResultsIn total 2808 patients were included, and 1671 (60%) were treated with BGC. No differences in the modified Rankin Scale score at 90 days were seen between non‐BGC and BGC groups (adjusted common odds ratio [OR], 0.98 [95% CI, 0.82–1.10]). The non‐BGC was associated with faster procedure times compared with BGC (adjusted β: −2.99 [95% CI, −5.58 to −0.40]). A significant treatment effect was found between BGC use and thrombectomy technique. In subgroup analyses with stent retriever as first‐line technique, 90‐day modified Rankin Scale scores were significantly higher (more disability) in the non‐BGC group compared with the BGC group (adjusted common OR, 0.79 [95% CI, 0.65–0.96]). Direct aspiration combined with non‐BGC resulted in higher first‐attempt rates compared with BGC (adjusted OR, 1.55 [95% CI, 1.06–2.28]).ConclusionsThis large prospective multicenter registry showed no differences in clinical outcome between patients treated with non‐BGC and BGC. Subgroup analyses suggest that BGC outperforms the non‐BGC when stent retriever is used as first‐line technique, whereas non‐BGC outperforms the BGC when aspiration is used.