Introduction Platelet reactivity measurements are commonly utilized in the perioperative phase of neurointerventional stenting procedures. Reliability and clinical decision strategies based on test results have been controversial. We examined fluctuations of platelet reactivity in response to Aspirin and Clopidogrel treatment on the day of the procedure and on postoperative day one.

Methods Medical records of patients undergoing neuroendovascular stenting procedures at our institution between 2012 and 2016 were included if platelet reactivity measurements were available (Verify Now, Accriva Diagnostics), and reviewed for the following data points: Patient age, sex, type of stent, stent location, Aspirin and Clopidogrel (P2Y12) inhibition on the day of the procedure and on postoperative day one, and occurrence of in-stent stenosis or occlusion on imaging follow up. Aspirin reactive unit (ARU) of less than 550 and P2Y12 reactive unit (PRU) of less than 190 was considered therapeutic platelet inhibition. All but one cases were performed under general anesthesia.

Results Data from 112 stenting procedures between 2012 until 2016 met inclusion criteria: 39 intracranial stents, 63 carotid stents, and 10 extracranial vertebral artery stents. The average patient age was 64 years (32–90) and 64 patients were male (57%). The average Aspirin inhibition on the day of the procedure was 451 ARU. Additional Aspirin was administered in 16 subtherapeutic cases (14%), with 14 positive responses (88%). On postoperative day one the average Aspirin inhibition was 464 ARU (3% decreased reactivity). While Aspirin inhibition decreased in 68 cases (60%), only 15 cases were subtherapeutic (13%). The average P2Y12 inhibition on the day of the procedure was 162 PRU. Additional Clopidogrel was administered in 28 subtherapeutic cases (25%), and one patient received prasugrel; only 6 patients exhibited a positive response (21%). On postoperative day one the average P2Y12 inhibition was 199 PRU (19% decreased reactivity), reaching overall subtherapeutic level. P2Y12 inhibition measurement decreased in 83 cases (74%), of which 67 cases were subtherapeutic (60%). The decreased measurement effect remains robust in 13 of 28 cases where additional Clopidogrel was administered (46%). Asymptomatic in-stent stenosis or occlusion was observed in 23 cases on imaging follow up (21%): Intracranial stent 9 (23%) with stent location in the intracranial internal carotid and vertebrobasilar arteries, cervical carotid stent (13%) and extracranial vertebral artery 3 (30%). Of cases with subsequent in-stent stenosis or occlusion 5 were measured with subtherapeutic P2Y12 inhibition on the day of the procedure (22%) and 11 on postoperative day one (48%); 4 were subtherapeutic on Aspirin on the day of the procedure (17%) and 1 on postoperative day one (4%).

Conclusions We observed a significant decrease of P2Y12 reactivity units on postoperative day one in our cohort of patients undergoing neurovascular stenting procedures. While the cause and clinical significance of this finding is uncertain and may be related to the use of general anesthesia, it appears that stent location (Intracranial internal carotid and vertebrobasilar arteries) is more closely related to the incidence of in-stent stenosis and occlusion than periprocedural fluctuations of platelet reactivity measurements.

Disclosures W. Leesch: 3; C; Penumbra Inc. 4; C; Cerebrotech Inc. 6; C; Stryker Corp, Penumbra Inc, Terumo Microvention, Medtronic. P. Ramakrishnan: None. F. Sanderson: None.