First-pass effect in posterior acute ischemic stroke undergoing endovascular thrombectomy: A systematic review and meta-analysis

Objectives: First-pass effect (FPE) has been shown to be a predictor of favorable clinical outcomes following endovascular thrombectomy (EVT) for acute ischemic stroke (AIS) in the anterior circulation. Literature regarding FPE for posterior circulation AIS is sparse; we conducted a systematic review and meta-analysis to explore FPE in posterior circulation stroke undergoing EVT. Materials and Methods: We conducted a systematic review of the English literature in PubMed, Embase, Scopus, and Web of Science. FPE was defined as thrombolysis in cerebral infarction (TICI) 2c-3 and modified FPE (mFPE) was defined as TICI 2b-3 in one pass. Definitions of non-FPE and non-mFPE varied among studies. The primary outcome of interest was modified Rankin Scale (mRS) 0-2. Secondary outcomes of interest were mRS 0-3, symptomatic intracranial hemorrhage (sICH), and mortality. We calculated odds ratios (OR) and corresponding 95% confidence intervals (CI). Heterogeneity was assessed with Q statistic and I² test. Results: Seven studies with 417 patients in the mFPE group, 942 in the non-mFPE group, 545 in the FPE group, and 1023 in the non-FPE group were included. Overall, FPE was associated with greater rates of 90-day mRS 0-2 (OR= 2.78, 95% CI= 2.11-3.65; P-value< 0.001) and mRS 0-3 (OR= 2.67, 95% CI= 1.98-3.60; P-value< 0.001); however, there was significant heterogeneity among studies for both mRS 0-2 (I²= 69%; P-value< 0.001) and mRS 0-3 (I²= 69%; P-value< 0.001). FPE and non-FPE were associated with similar rates of sICH (OR= 0.65, 95% CI= 0.40-1.07; P-value= 0.09), and no heterogeneity was observed (I²= 0%; P-value= 0.95). FPE was associated with lower rates of mortality (OR= 0.44, 95% CI= 0.33-0.58; P-value< 0.001), although heterogeneity was observed (I²= 58%; P-value= 0.01). Conclusions: FPE is associated with favorable clinical outcomes in patients undergoing EVT for posterior circulation AIS. Future studies should work to further quantify the impact of FPE on outcomes in the posterior circulation.