"Mechanical thrombectomy beyond 6 hours for acute ischemic strokes due to M2 occlusions".

Background: The time frame for mechanical thrombectomy (MT) in acute ischemic stroke (AIS) is enlarging. Guidelines recommend MT until 6 h of symptom onset in M2 segment occlusions (grade IIB). In practice, it is frequently performed later.

Aims: To assess the functional prognosis of AIS patients subjected to M2 segment's MT beyond 6 h, compared to standard intervention.

Methods: Retrospective cohort study including all consecutive AIS patients subjected to MT of M2 occlusions between 1st January 2018 and 31st December 2020 in St Joseph's Local Health Unit, Lisbon, Portugal. Allocation to standard or extended groups was done according to the symptom-to-puncture time, whether within or beyond 6 h after symptom onset, respectively. The primary outcome was the modified Rankin Scale (mRS) at three months. Secondary outcomes were symptomatic intracranial hemorrhage (sICH) at 24 h and three-month mortality.

Results: We included 155 patients, 51.0 % men, median age 76.0 years (P₂₅:69.0;P₇₅:86.0), baseline mRS "0-2" in 84.5 %, mean NIHSS 13.6(6.5). Initial Computed Tomography showed early ischemic changes in 27.1 %. Most patients belonged to the standard group (71.0 %). Groups had similar baseline features. The standard group underwent more frequent (68.2 % vs 44.4 %, p = 0.006) and earlier (2 h02 min, 3 h02 min, p < 0.001) fibrinolysis. Symptom-to-puncture times were 7 h13 min (extended) and 4h01 min (standard), p < 0.001. Outcomes were similar between groups (three months' mRS [p = 0.578]; sICH [p = 0.720]; three-month mortality [p = 0.422]).

Conclusions: Our study suggests similar outcomes in M2 occlusions performing MT before and beyond 6 h of symptom onset, consistent with previous studies. Patients might benefit from widening inclusion criteria for MT in AIS.