Dual Antiplatelet Non-Responder: Resistance to Clopidogrel and Ticagrelor.

Background: Dual antiplatelet therapy is often required for neurointerventional procedures, especially when a stent or flow diverter is placed in the cervical and intracranial vessels. Patients are usually started on aspirin and clopidogrel given the simplicity of the once daily regimen with reasonable cost. Unfortunately, about a third of patients do not show the desired antiplatelet response to clopidogrel and another agent needs to be introduced. Ticagrelor is a potent antiplatelet medication that has a favorable pharmacological profile and has emerged as a reliable alternative to clopidogrel in recent years. Despite ticagrelor non-responders being rare, they do exist, and identification of these patients is important.

Results: A 74-year-old female was incidentally found to harbor a right posterior communicating aneurysm which was successfully treated electively with stent-assisted coiling. Platelet inhibition testing revealed non-responsiveness to Clopidogrel. Ticagrelor was initiated but the patient's platelet reactivity unit remained in the normal range. Management algorithms to maximize a patient's ticagrelor response by facilitating enteral absorption were applied but no platelet inhibition was achieved. The patient was eventually identified as a true ticagrelor non-responder.

Conclusion: Resistance to antiplatelet medication can result in devastating complications with permanent neurological deficits. Ticagrelor non-responders are rare but do exist. Platelet inhibition testing should be part of the preprocedural workup for neurointerventions.