Systematic Literature Review of Mechanical Thrombectomy treatment of Acute Ischemic Stroke

Background: High-quality evidence exists for mechanical thrombectomy (MT) treatment of acute ischemic stroke (AIS) due to large vessel occlusion of the anterior circulation (AC-LVO). The evidence for MT treatment of posterior circulation large vessel occlusion (PC-LVO) is weaker, largely drawn from lower quality studies specific to PC-LVO and extrapolated from findings in AC-LVO, and ambiguous with regards to technical success. We performed a systematic review and meta-analysis to compare the technical success and functional outcomes of MT in PC-LVO versus AC-LVO patients.

Methods: We identified comparative studies reporting on patients treated with MT in AC-LVO versus PC-LVO. The primary outcome of interest was thrombolysis in cerebral infarction (TICI) ≥ 2b. Secondary outcomes included rates of TICI 3, 90-day functional independence, first-pass-effect, average number of passes, and 90-day mortality. A separate random effects model was fit for each outcome measure. Subgroup analyses were performed comparing studies with recruitment periods prior to 2014 versus after 2014.

Results: Twenty studies with 12,911 patients, 11,299 (87.5%) in the AC-LVO arm and 1,612 (12.5%) in the PC-LVO arm, were included. AC-LVO and PC-LVO patients had comparable rates of successful recanalization [OR=1.02 [95% CI: 0.79–1.33], p=0.848). However, the AC-LVO group had greater odds of functional independence at 90 days (OR=1.26 [95% CI: 1.00; 1.59], p=0.050) and lower odds of mortality at 90 days (OR=0.58 [95% CI: 0.43; 0.79], p=0.002). In the subgroup analysis, AC-LVO patients (51.8% [95% CI: 38.4–64.8]) were found to achieve functional independence more often than PC-LVO (40.7% [95% CI: 21.8–62.8%]) patients treated after 2014, but this effect was not observed prior to 2014.

Conclusions: MT achieves similar rates of recanalization with a similar safety profile in PC-LVO and AC-LVO patients. Patients with PC-LVO are less likely to achieve functional independence after MT. Future studies should identify PC-LVO patients who are likely to achieve favorable functional outcomes or those in whom MT is futile.

Key Insights:

Mortality in Thrombectomy patients unaffected by Standard Medical Therapy

The odds of Mortality for Mechanical thrombectomy were 1.01 times as likely as Mechanical Thrombectomy with concomitant intravenous Thrombolysis (95% CI [0.852, 1.21]) across 5,511 patients. There was no significant difference in the rate of mortality between these two therapeutic groups (18.6% [16.5%, 20.8%] for Thrombectomy vs. 14.3% [11.9%, 17.0%]).

Parent artery location was equivalent across therapies

For Thrombolysis, Thrombectomy, or Thrombectomy with concomitant Thrombolysis, the rates of clot presence in the ICA was between 15% and 20%, the rate of clot presence in the MCA was between 65% and 70%, and all other occlusions were Tandem Occlusions. No significant differences were found among parent artery locations.

Thrombectomy significantly improves Neurological Outcomes

Across 6,456 patients, Good Neurological Outcome (modified Rankin Scale Score of 0-2) was significantly higher for Thrombectomy than Thrombolysis (47.5% [44.5%, 50.5%] vs. 29.3% [23.3%, 36.2%]), with an Odds Ratio of 2.43 : 1 (95% CI [1.91, 3.09]).