Introduction: The role of platelet function testing in the management of periprocedural antiplatelet medications for flow diversion of intracranial aneurysms remains incompletely understood. Therefore, the aims of this retrospective cohort study are to evaluate the results of preoperative platelet function testing in aneurysm patients undergoing flow diversion and to determine their effect on aneurysm occlusion and complications.

Methods: We retrospectively evaluated a prospectively maintained database of aneurysm patients who underwent flow diversion with the Pipeline Embolization Device at our institution from 2009-2017. Patients who underwent preoperative platelet function testing with aspirin or P2Y12 assays were included. Aspirin and clopidogrel non-responders (NR) were defined as aspirin reaction units (ARU) =550 and P2Y12 reaction units (PRU) =200, respectively.

Results: The study cohort included 104 patients with platelet function testing data. P2Y12 and aspirin assays were performed in 104 and 80 patients, respectively. Five patients were aspirin NRs (6%); of this subgroup, 60% achieved complete aneurysm occlusion and 40% presented with acute thromboembolic complications (ATC). The mean P2Y12 reaction units (PRU) was 138 (range:1.5-452), including 28% clopidogrel NRs. In the clopidogrel NR group, 78% (21/29 patients) were switched from clopidogrel to prasugrel 10 mg daily. Of these, 81% (17/21 patients) had aneurysm occlusion and 14% (3/21 patients) had ATCs. By comparison, clopidogrel NR patients who were not switched to prasugrel had a similar aneurysm occlusion rate of 88% (7/8 patients; P=0.65) and non-significantly higher ATC rate of 25% (2/8 patients; P=0.60). No hemorrhagic complications were noted in these patients.

Conclusions: Although aspirin NRs are rare, the relatively elevated rate of ATCs after flow diversion in these patients suggests that switching them to alternate antiplatelet medications may be warranted. Switching clopidogrel NRs to prasugrel may reduce the risk of ATCs, although further analyses of larger cohorts are necessary to validate this approach in aneurysm patients undergoing flow diversion.

Patient Care: The appropriate management of antiplatelet medications is an important aspect of flow diversion for intracranial aneurysms. Platelet function testing can help to guide the prescription of effective antiplatelet regimens.

Learning Objectives: By the conclusion of this session, participants should be able to 1) Describe the importance of preoperative platelet function testing for flow diversion of intracranial aneurysms, 2) Discuss, in small groups, the outcomes of patients who are hyporesponders to aspirin and clopidogrel, and 3) Identify an effective strategy for managing hyporesponsiveness to aspirin and clopidogrel.

References: 1. Daou B, Starke RM, Chalouhi N, et al. P2Y12 Reaction Units: Effect on Hemorrhagic and Thromboembolic Complications in Patients With Cerebral Aneurysms Treated With the Pipeline Embolization Device. Neurosurgery. Jan 2016;78(1):27-33. 2. Adeeb N, Griessenauer CJ, Foreman PM, et al. Use of Platelet Function Testing Before Pipeline Embolization Device Placement: A Multicenter Cohort Study. Stroke; a journal of cerebral circulation. May 2017;48(5):1322-1330. 3. Atallah E, Saad H, Bekelis K, et al. The use of alternatives to clopidogrel in flow-diversion treatment with the Pipeline embolization device. Journal of neurosurgery. Dec 8 2017:1-6.