Long-term Safety and Efficacy of Pipeline Embolization Device (PED) in Anterior versus Posterior Aneurysms: A Systematic Review and Meta-analysis

Introduction: Flow diversion using the Pipeline Embolization Device (PED) has been a paradigm shift for anterior circulation(AC) aneurysms. However, only a few studies in the literature report the long-term (≥1 year) angiographic and clinical outcomes for posterior circulation(PC) aneurysms. The objective of this study was to compare the long-term morbidity and occlusion rate between AC and PC aneurysms treated with PED.

Methods: We performed a systematic review of the literature and meta-analysis of studies that reported anterior or posterior circulation aneurysms treated with PED. Studies with at least 10 patients and 1-year follow-up were included. The primary safety endpoints were the rate of cumulative symptomatic stroke, intracranial hemorrhage, and aneurysm rupture. The primary efficacy endpoint was the complete aneurysm occlusion rate.

Results: Twenty-four studies met our inclusion criteria. There were 1,835 patients with 1,952 aneurysms, of which 1547 were in the AC, and 405 were in the PC. One-year occlusion rate was 78% (95%,CI 70%-84%) in AC compared to 73% (95%CI 67%-78%) in PC (p < 0.01) after PED treatment. The silent stroke rate was 3% (95%CI 2%-6%) in anterior vs 5% (95%,CI 2%-8%) in posterior aneurysms (p=0.01). The symptomatic infarct rate was 5% (95%CI 4%-7%) in AC compared to 13% (95%CI 7%-23%) in PC aneurysms (p < 0.01). The long-term rate of aneurysm rupture was 1% (95%CI 1%-2%) in the AC compared to 4% (95%CI 2%-9%) in the PC aneurysms (p=0.01). Finally, the rate of intracranial hemorrhage in AC vs. PC aneurysms was 2% for both (p=0.99).

Conclusion : Long-term occlusion rate was higher in AC aneurysms after PED placement and the rate of complications, specifically thromboembolic stroke and aneurysm rupture was significantly higher in PC aneurysms. However, the intracranial hemorrhage rate was not different between AC and PC aneurysms. Further evaluation of factors predisposing to incomplete occlusion and post-procedural complications after PED placement is needed.