Inclusion Criteria1. New ischemic stroke with disabling neurological deficit or lesion diameter on brain imaging > 1.5 cm.
2. Non-valvular atrial fibrillation (paroxysmal, persistent, or permanent).
3. Not currently anticoagulated (except for DVT prophylaxis).
4. Treating physician plans to anticoagulate with a novel oral anticoagulant (NOAC): apixaban, dabigatran, edoxaban, or rivaroxaban, or other NOAC.
5. Qualifying brain CT or MRI scan < 48hr from stroke onset (time last known well). If patient has been treated with thrombolytic or endovascular therapy for this stroke, then the qualifying scan is performed 18-36 hours after therapy to rule out clinically significant hemorrhagic transformation. This group of patients must have their qualifying NIHSS assessment performed at the time of this scan.
6. Ability to randomize within 60 hours of symptom onset.
Exclusion Criteria1. Primary intracerebral hemorrhage on qualifying neuroimaging. Note: Hemorrhagic transformation of a primarily ischemic stroke may be included as per Investigator`s judgment. Sporadic microbleeds may be included as per Investigator`s judgment. As a general recommendation, a cerebral microbleed is considered to be ≤ 5mm, but sometimes up to 10mm, in greatest diameter on gradient recalled echo (GRE), or T2*, MRI sequences. Any blood visualized on a CT will be classified as a macrobleed
2. Infarct volume (estimated) is greater than 50% of middle cerebral artery territory on qualifying scan.
3. NIHSS < 4 or > 23 prior to enrollment. Note: For patients that had thrombolytic or endovascular therapy, the qualifying NIHSS assessment is that which is obtained concurrently with their qualifying scan 18 -36 hours following therapy.
4. Anticipated need for major surgery over the next 30 days that would require delay, discontinuation, or extended suspension of anticoagulant.
5. Symptomatic edema expected from size and location of ischemic stroke.
6. Decreased level of consciousness present or expected.
7. Any intracranial hemorrhage within the previous 6 months.
8. Life expectancy less than 90 days.
9. Follow-up in person or by telephone for 90 days is not feasible.