Evidence regarding the role of early (<24 hours) antithrombotics post-revascularization with either intravenous thrombolysis (IVT), endovascular thrombectomy (EVT), or a combination of both remains scarce. In 2018 the American Heart Association/American Stroke Association changed their recommendation, stating that the risk of antithrombotic therapy within the first 24 hours after treatment with IVT (with or without EVT) is uncertain. This was changed after data emerged that early antithrombotics may be safe and may improve outcomes in select patients undergoing EVT.

Recently the investigators showed for the first time that significant residual basilar thrombus can exist after EVT despite complete angiographic revascularization using endovascular optical coherence tomography imaging. This residual thrombus could cause ongoing function-limiting strokes with occlusion of vital basilar perforators after EVT. Therefore, the investigators propose a prospective,non-randomized safety study to evaluate optical coherence tomography guided antithrombotic management for patients with confirmed residual thrombus after EVT for basilar occlusion.

Inclusion Criteria:

- All patients deemed candidates for endovascular thrombectomy(EVT) for basilar artery occlusion. As no robust guidelines exist for the role of EVT in patients with acute basilar artery occlusion, the decision for EVT is made by a team of stroke neurologist and neuro-interventionalist at our regional stroke center.

Exclusion Criteria:

• High-density lesion consistent with hemorrhage of any degree.
• Significant established infarct size.
• Contraindication to receiving post-revascularization antithrombotics for any reason (history of major hemorrhage in the past six months, hereditary or acquired bleeding diathesis, major surgery within last three months, platelets <100 X 109 /L, coagulation factor deficiency, already on anticoagulant that would not allow administration of UFH)
• Informed consent is not or cannot be obtained.
• Females of childbearing potential who are known to be pregnant and/or lactating or who have positive pregnancy tests on admission.
• Other serious, advanced, or terminal illness.
• Patients who require hemodialysis or peritoneal dialysis.
• Uncontrolled hypertension defined as systolic blood pressure>185 mm Hg or diastolic blood pressure>110mm Hg that cannot be controlled except with continuous parenteral antihypertensive medication