Low radial and axial force stent retriever reduces symptomatic subarachnoid hemorrhage after mechanical thrombectomy for acute middle cerebral artery and medium vessel occlusion: a prospective pilot study.

Background: Subarachnoid hemorrhage (SAH) is a well-recognized complication after mechanical thrombectomy (MT) and may adversely affect clinical outcomes. SAH commonly results from vessel injury due to overextension or displacement during device retrieval. This risk is particularly concerning in smaller, tortuous vessels, such as in medium vessel occlusions (MeVO). This study evaluated whether a novel low radial and axial force stent retriever (Tron FX II) could reduce post-procedural SAH without compromising recanalization outcomes. Methods: The study comprised two components: (1) bench testing comparing radial/axial force and vessel displacement during retrieval between Tron FX II (hereafter Tron) and conventional devices; and (2) a prospective observational study of 197 consecutive MT patients. A combined technique was employed in all cases. Conventional stent retrievers were used until July 2023, after which Tron was used exclusively. Post-procedural SAH was assessed using dual-energy CT immediately after MT. The primary outcome was SAH incidence, with or without symptoms. Secondary outcomes included effective recanalization, first-pass rate, and 90-day functional outcomes. Results: Bench testing showed Tron exhibited the lowest radial/axial force and the smallest vessel deviation during retrieval. Clinically, Tron significantly reduced the incidence of post-procedural SAH (7.7% vs. 23.9%, p = 0.027) as well as SAH associated with neurological deterioration (1.9% vs. 12.7%, p = 0.044) in cases of middle cerebral artery occlusion (MCAO) and MeVO. Moreover, both Tron use and fewer stent retriever passes were independently associated with a lower risk of SAH. Overall effective recanalization, first-pass rates, and functional outcomes were not significantly different between groups in this pilot study. Conclusion: The low radial and axial force stent retriever reduced post-procedural SAH while maintaining effective recanalization when combined with an aspiration catheter. These findings support its potential role as a safer option for MCAO and MeVO.