P-006 Initial Response to Aspirin Therapy Measured with the PFA-100 Assay in Patients Undergoing Endovascular Treatment of Unruptured Cerebral Aneurysms

Background and purpose Recent studies have examined the variability in response to clopidogrel therapy in patients undergoing endovascular treatment of unruptured cerebral aneurysms; however, no study has systematically assessed patient response to aspirin therapy in this patient population. This study aims to determine the initial response to aspirin therapy in patients undergoing endovascular treatment of unruptured cerebral aneurysms. Methods We retrospectively reviewed the results of platelet function testing in a cohort of patients who were started on aspirin therapy for the endovascular treatment of unruptured cerebral aneurysms at our institution from November 17th, 2011 until March 13th, 2014. Baseline patient characteristics, aspirin dosing and thromboembolic complications were recorded. Patient response to aspirin therapy was assessed with the PFA-100 assay before the procedure, with ≥50% inhibition defined as an appropriate platelet response. Results One-hundred and seventeen patients were included in the study, 23 male (20%) and 94 female (80%), mean age 56 years (25–84 years). The patients included in this cohort comprised 52.5% of patients who underwent treatment of an unruptured cerebral aneurysm at our institution during the study period. Forty-eight patients were active smokers (41%), 72 had a history of hypertension (62%) and 6 diabetes mellitus (5%). Sixty-two patients were treated with simple or balloon-assisted coiling (53%), 43 with the Pipeline Embolization Device (37%) and 12 with a stent (10%). Fifty-three patients were started on 325 mg aspirin (45%), 50 on 81mg enteric-coated aspirin (43%), and 14 on 81 mg non-enteric-coated aspirin (12%). Mean number of aspirin doses before the initial PFA-100 test was 11.5 (median 9, range 3–29). Overall, mean initial platelet inhibition was 68.2% (median 70.5%, range 20.5–94.6%), with a significantly-lower mean inhibition in patients taking 81mg enteric-coated aspirin (62.5%) compared to those taking 81 mg non-enteric-coated aspirin (72.1%, p-value 0.049) and 325 mg aspirin (72.5%, p-value 0.001). Overall, 13 patients were considered to be non-responders to aspirin therapy in the initial PFA-100 test (11.1%), most of whom were taking 81mg enteric-coated aspirin (9, 69%). There was a significantly-increased likelihood of an initial non-response to aspirin therapy among patients taking 81 mg enteric-coated aspirin (18%) compared to those taking 81 mg non-enteric-coated aspirin (7.1%) and 325 mg aspirin (5.7%, p-value 0.04). In multivariate logistic regression analysis, an 81 mg enteric-coated aspirin dose was the only independent predictor of an initial non-response to aspirin therapy in our cohort (odds ratio 0.52, 95% confidence interval 0.28–0.98, p-value 0.043). There were 7 thromboembolic complications in our cohort (6%), none of which caused a permanent disabling neurological deficit or death. All of the patients who experienced a thromboembolic complication had demonstrated an appropriate platelet response to aspirin therapy in pre-procedure testing. Conclusion Performing pre-procedure platelet function testing in patients taking 81 mg enteric-coated aspirin to ensure an adequate platelet response to aspirin therapy may be prudent prior to undertaking endovascular treatment of an unruptured cerebral aneurysm. Disclosures J. Delgado Almandoz: 2; C; Covidien/ev3, Microvention/Terumo. Y. Kadkhodayan: 2; C; Covidien/ev3. J. Scholz: None. J. Fease: None. A. Blem: None. K. Tran: None. B. Crandall: 2; C; Covidien/ev3.