Background The benefit, safety, and time intervals of mechanical thrombectomy (MT) in patients with in-hospital stroke (IHS) are unclear. We sought to evaluate the outcomes and treatment times for IHS patients compared with out-of-hospital stroke (OHS) patients receiving MT.

Methods We analyzed data from the Italian Registry of Endovascular Treatment in Acute Stroke (IRETAS) between 2015 and 2019. We compared the functional outcomes (modified Rankin Scale (mRS) scores) at 3 months, recanalization rates, and symptomatic intracranial hemorrhage (sICH) after MT. Time intervals from stroke onset-to-imaging, onset-to-groin, and onset-to-end MT were recorded for both groups, as were door-to-imaging and door-to-groin for OHS. A multivariate analysis was performed.

Results Of 5619 patients, 406 (7.2%) had IHS. At 3 months, IHS patients had a lower rate of mRS 0–2 (39% vs 48%, P<0.001) and higher mortality (30.1% vs 19.6%, P<0.001). Recanalization rates and sICH were similar. Time intervals (min, median (IQR)) from stroke onset-to-imaging, onset-to-groin, and onset-to-end MT were favorable for IHS (60 (34–106) vs 123 (89–188.5); 150 (105–220) vs 220 (168–294); 227 (164–303) vs 293 (230–370); all P<0.001), whereas OHS had lower door-to-imaging and door-to-groin times compared with stroke onset-to-imaging and onset-to-groin for IHS (29 (20–44) vs 60 (34–106), P<0.001; 113 (84–151) vs 150 (105–220); P<0.001). After adjustment, IHS was associated with higher mortality (aOR 1.77, 95% CI 1.33 to 2.35, P<0.001) and a shift towards worse functional outcomes in the ordinal analysis (aOR 1.32, 95% CI 1.06 to 1.66, P=0.015).

Conclusion Despite favorable time intervals for MT, IHS patients had worse functional outcomes than OHS patients. Delays in IHS management were detected.