Patterns, Predictors, and Outcomes of Postprocedure Delayed Hemorrhage Following Flow Diversion for Intracranial Aneurysm Treatment.

OBJECTIVE:To evaluate patterns, predictors, and outcomes of postprocedure delayed hemorrhage (PPDH) following flow diversion therapy for intracranial aneurysm treatment. METHODS:From 2012 to 2016, 50 patients with 52 aneurysms were treated with the Pipeline embolization device. Device placement was performed as a standalone therapy or with adjunctive coil embolization. Patients underwent dual antiplatelet therapy for 6 months after treatment. Medical comorbidities; aneurysm traits; and treatment factors, including platelet function testing, were studied. Statistical analysis was performed using cross-tabulation. RESULTS:Six PPDHs (12%) occurred 2-16 days (mean 6.8 days) after Pipeline placement, manifesting as 1 of 2 distinct patterns: convexity subarachnoid hemorrhage (cSAH) (n = 4) or lobar intraparenchymal hemorrhage (IPH) (n = 2). All PPDHs occurred ipsilateral to the device; 1 IPH occurred ipsilateral but in a different arterial territory. PPDH occurred in both treated anterior communicating artery aneurysms. Cases of PPDH demonstrated on average lower P2Y12 reaction unit values at the time of treatment. Platelet function testing at the time of hemorrhage was consistently hypertherapeutic. Patients with cSAH had only minimal worsening of modified Rankin Scale score at the time of discharge, whereas the 2 patients with IPH experienced significant deterioration. CONCLUSIONS:PPDH is a poorly understood complication following flow diversion therapy that can result in significant morbidity. In our experience, nonaneurysmal cSAH does not result in poor clinical outcomes, whereas IPH leads to long-term deficits or death. As previously suggested, there appears to be a correlation between low P2Y12 reaction unit values and PPDH.