Abstract 1122‐000043: Vorapaxar as An Alternative for Ticagrelor Resistance in Neuroendovascular Intervention
Authors: Mamaril‐Davis James C , Aguilar‐Salinas Pedro , Brasiliense Leonardo , Cosgrove Richard , Dumont Travis , El‐Ghanem Mohammad 
Published: December 2021

Introduction
: Perioperative dual‐antiplatelet therapy (DAPT) for flow diversion (FD) limits thromboembolic complications. Practice of DAPT varies across the neuroendovascular field but typically includes aspirin and an ADP receptor antagonist such as clopidogrel, prasugrel, or ticagrelor. Unfortunately, resistance to DAPT medications remains a concern for neuroendovascular intervention, and there is a current lack of standard alternatives for such resistance. The main goal of this abstract is to discuss ticagrelor resistance and to inform possible therapeutic options.

Methods
: We report a case of vorapaxar treated FD for an intracranial aneurysm in a patient with ticagrelor resistance. FD was deployed for a left internal carotid artery (ICA) blister aneurysm and bilateral ICA dissecting pseudoaneurysms (Figure 1). We also provide a narrative review on previous reports of ticagrelor resistance and associated treatment responses. We used the keywords: “ticagrelor,” “resistance,” “hypo‐response,” “stent thrombosis,” and “aneurysm.” These were implemented in various combinations with Boolean operators in three databases: PubMed, Ovid MEDLINE, and Ovid EMBASE.

Results
: During a complicated clinical course, the patient had three thromboembolic complications while on DAPT with ticagrelor or prasugrel leading to transition of antiplatelet therapy to vorapaxar. Thromboelastography with platelet mapping (TEG‐PM) routinely demonstrated inadequate platelet inhibition, which was confirmed with platelet function analyzer‐100. Initial TEG‐PM results were 0.0% ADP receptor inhibition and MA‐ADP of 62.2 mm. Repeat angiograms also indicated thromboembolic formation after each of the three events (Figure 1). After introduction of vorapaxar, the patient had adequate platelet inhibition with TEG‐PM results of 49.1% ADP receptor inhibition and MA‐ADP of 48.3 mm. At 84 days follow‐up, the patient was fully recovered with complete occlusion of the aneurysms. In a narrative review of the literature, there were ten previously reported cases of ticagrelor resistance or hypo‐response: three cases in the neuroendovascular literature and seven cases in the cardiovascular literature. Among all of the cases, there was a variability in protocol for treating patients with suggested ticagrelor resistance. All three neuroendovascular cases either employed another ADP receptor antagonist in hopes that the resistance would not generalize or eliminated DAPT altogether and settled for aspirin alone. In some of the cardiovascular cases, ticagrelor was even continued after patients exhibited laboratory evidence of resistance or hypo‐response.

Conclusions
: Given the paucity of cases describing ticagrelor resistance or hypo‐response in the neuroendovascular and cardiovascular literature, management of DAPT should remain a multifactorial decision depending on the clinical situation. Moreover, we need to consider therapeutic alternatives for cases of resistance such as thrombin receptor antagonists, specifically PAR1 receptor antagonists like vorapaxar. High quality randomized controlled trials are needed to elucidate the safety and efficacy of vorapaxar in neuroendovascular procedures.