Carotid artery stenting (CAS) is a key treatment option for moderate to severe carotid artery stenosis. Carotid stent thrombosis (CST), a rare complication of CAS, has gained significant attention because of its catastrophic nature. More evidences are needed to guide the diagnosis and treatment of CST.

This study reports a rare case of sub-acute CST following CAS in a 50-year-old male patient who had experienced repeated cerebrovascular events on the premise of taking antiplatelet drugs. He also suffered an occlusion of the left middle cerebral artery (MCA) in the M2 segment, likely caused by an embolus detached from the stent thrombus. The cause of CST in this patient was presumed to be dual antiplatelet resistance (AR), as indicated by genetic testing. After treated with guide catheter-directed thrombolysis, thrombus aspiration, and a second round of thrombolysis, his in-stent thrombus was basically cleared. His M2 occlusion was resolved by mechanical thrombectomy using the Solitaire FR/Stent with Intermediate Catheter Assisting technique. The patient recovered well after replacement of antiplatelet drugs, and no new thromboembolic event occurred during the 13-month follow-up period.

The occurrence rate of AR-related CST may be underestimated as the cause of majority CST cases remains unclear. Implementation of genetic test for aspirin and clopidogrel resistance may be helpful to find the possible cause of CST and to avoid future repeated cerebrovascular events by replacement of antiplatelet drugs.

Objective: A rare case of thromboembolic cerebral infarction due to carotid web in a patient with congenital protein C deficiency is reported. Case Presentation: A patient in her 40's with left-side hemiparesis was transferred to our hospital under continuous intravenous injection of heparin. Magnetic resonance angiography demonstrated occlusion of the right middle cerebral artery (MCA). Conventional angiography revealed recanalization of the right MCA and a carotid web at the origin of the right internal carotid artery. Ultrasound scan of the carotid artery on the 19th day revealed thrombus formation on the distal portion of the carotid web. We performed carotid artery stenting to prevent thrombus formation by suppressing the carotid web to the vessel wall and by regulating the turbulent flow. The patient had no recurrence of stroke under-anticoagulation with warfarin during the 2-year follow-up period. Conclusion: To our knowledge, this is the first report in which an immediate thrombus formation on the carotid web was observed in a patient with congenital protein C deficiency. In a case of acute ischemic stroke with carotid web, especially when congenital coagulopathy such as protein C deficiency is suspected, careful follow-up with ultrasound imaging should be performed.

Carotid angioplasty and stenting (CAS) represents an effective procedure for treating carotid artery disease. The acute in-stent thrombosis is an extremely rare complication of CAS especially when it occurs postprocedurally during the first 24 hours. Improper antiplatelet therapy or poor response to antiplatelet medications is known to be associated with a higher risk of in-stent thrombosis during early postprocedural period following a successful intervention.

A patient who experienced acute carotid in-stent thrombosis in early postprocedural period is described. He had been taking dual antiplatelet therapy for 2 weeks before undergoing a successful CAS. Moreover, pharmacogenetics studies showed the patient to be a clopidogrel ultrarapid metabolizer, which theoretically confers hyperresponsivity to medication. Alongside the report itself, a brief literature review of relevant sources pertinent to the case has been conducted.

According to the available literature, this is the first case report describing an ultrarapid clopidogrel metabolizer who underwent an uneventful CAS but experienced acute carotid in-stent thrombosis in early postprocedural period. A rescue procedure included an endovascular intervention consisting of thrombectomy and local alteplase application, followed by postprocedural administration of intravenous eptifibatide. At discharge, patient's dual antiplatelet therapy included ticagrelor instead of clopidogrel.

Acute carotid in-stent thrombosis is a highly unexpected complication of CAS and can occur despite ultrarapid clopidogrel metabolism trait.