O-018 Variability in Response to a 75mg Daily Clopidogrel Dose in a Cohort of 90 Patients Undergoing Endovascular Treatment of Unruptured Cerebral Aneurysms

Background and Purpose Recent studies have suggested that variability in response to clopidogrel therapy may explain some of the thromboembolic and hemorrhagic complications encountered after endovascular treatment of cerebral aneurysms with flow-diversion or stent-assistance. This study aims to determine the variability in response to a 75mg daily clopidogrel dose measured with VerifyNow in a cohort of patients undergoing endovascular treatment of unruptured cerebral aneurysms. Methods We performed a retrospective review of all patients who were started on a daily 75mg clopidogrel dose 7 to 10 days prior to endovascular treatment of a cerebral aneurysm and had the response to clopidogrel therapy measured with VerifyNow prior to the procedure over a 15-month period. Baseline clinical characteristics, concurrent medications and routine pre-operative laboratory values were collected. Changes in response to the daily 75mg clopidogrel dose in patients who underwent follow-up VerifyNow testing were also recorded. The target P2Y12 receptor inhibition range was 60–240 P2Y12 reaction units (PRU), with a PRU>240 considered a hypo-response to clopidogrel therapy (P2Y12 receptor under-inhibition), and a PRU Results Ninety patients were included in the study, 66 female (73.3%) and 24 male (26.7%). Mean age was 57.4 years (median 59.9 years, range 25–82 years). Mean pre-procedure PRU value after 6–9 75mg clopidogrel doses was 140.1 (median 143 PRU, range 3–399 PRU). Eighteen patients exhibited a hyper-response to clopidogrel therapy (20%, PRU 240, figure). There was a trend toward an increased likelihood of a hyper-response to clopidogrel therapy among female patients (24.2%) compared to male patients (8.3%, p-value 0.14). Overall, 39.4% of female patients and 25% of male patients were outside the target P2Y12 receptor inhibition range in pre-procedure VerifyNow testing. Follow-up VerifyNow testing was performed in 32 patients (35.6%), which revealed that 33.3% of patients who had initially been within the target PRU range exhibited a “conversion” to a hyper-response to a daily 75mg clopidogrel dose (mean 15.2 PRU, median 8 PRU, range 1–59 PRU). We found no increased likelihood of P2Y12 receptor over-inhibition in patients on a selective serotonin reuptake inhibitor (18.8%), or P2Y12 receptor under-inhibition in patients on a proton pump inhibitor (9.1%). Conclusion We found wide variability in patient response after 6–9 daily 75mg clopidogrel doses, with 20% of patients exhibiting P2Y12 receptor over-inhibition (PRU>60) and 16% of patients exhibiting P2Y12 receptor under-inhibition (PRU>240). Disclosures J. Delgado Almandoz: 2; C; Covidien/ev3. Y. Kadkhodayan: None. J. Scholz: None. B. Crandall: 2; C; Covidien/ev3. J. Fease: None. R. Anderson: None. D. Tubman: 2; C; Covidien/ev3, MicroVention.