Long-term Safety and Efficacy of the Pipeline Embolization Device in Small versus Large Aneurysms: A Systematic Review and Meta-analysis

Introduction: Flow diversion using the Pipeline Embolization Device (PED) is increasingly used for intracranial aneurysms achieving high obliteration rates with low morbidity. However, long-term (≥1 year) angiographic and clinical outcomes require further investigation. Our study aims to compare long-term aneurysm occlusion rates and clinical complications for patients with small ( < 10 mm) versus large (10-25 mm) aneurysms treated with PED.

Methods: We performed a systematic literature review and meta-analysis of studies including at least 10 patients treated with PED for small vs. large aneurysms and with at least 12 months follow-up. The primary safety endpoint was the rate of clinical complications measured by the presence of symptomatic stroke (confirmed clinically and radiographically), intracranial hemorrhage, or aneurysm rupture. The primary efficacy endpoint was complete aneurysm occlusion rate.

Results: Our analysis included 19 studies with 1,277 patients harboring 1,493 aneurysms. Of those, 1,378 aneurysms met our inclusion criteria. Mean age was 53.9 years. Most patients were women (79.1%) and most aneurysms were small (89.75%). The long-term occlusion rate was 73% (95%,CI 65%-80%) in small compared to 84% (95%,CI 76%-90%) in large aneurysms (p < 0.01). Long-term symptomatic thromboembolic rate was 5% (95%,CI 3%-9%) in small compared to 7% (95%,CI 4%-13%) in large aneurysms. (p=0.01). The rupture rate was 2% vs. 7% (p = 0.69), and the rate of intracranial hemorrhage was 2% vs. 4% (p=0.96) for small vs. large aneurysms respectively; however, these differences were not statistically significant.

Conclusion : Long-term occlusion rate after PED treatment is higher in large vs. small aneurysms. Also, thromboembolic symptomatic stroke rates are higher in large vs. small aneurysms. The difference in aneurysm rupture and intracranial hemorrhage rate was not significant. Although the PED seems a safe and effective treatment for small and large aneurysms, further studies are required to clarify how occlusion rate and morbidity are affected by aneurysm size.