When patients with atrial fibrillation suffer from an acute ischemic stroke, it is important to weigh the risk of hemorrhagic transformation against the risk of recurrent ischemic stroke in the immediate post-stroke period. It is unclear what the optimal timing of re-initiation is, and most guidelines are based on observational data with limited randomized controlled trials. One large international trial estimated a risk of 4.9% for recurrent stroke within 14 days of acute ischemic stroke in patients with atrial fibrillation, while an estimated risk of recurrent stroke in the first two weeks was 0.5-1.3% per day. Predictive factors included left atrial enlargement, older age, higher CHADS2VASC, and larger ischemic lesion size of the initial stroke. In predicting hemorrhagic transformation, it seems both the size of the lesion and the use of reperfusion therapy increased risk. Though there is limited data for the optimal timing of initiation, particularly with DOACs, one study (RAF-NOACs) seemed to suggest that initiation within 2 days of the ischemic event had a higher rate of major bleeding and stroke recurrence than initiation after 2 days; subsequent pooled analyses examined patients who all had a DOAC restarted within 14 days of the initial event, which has played a role in current guidelines. There are several ongoing randomized controlled trials examining this question, and results are anticipated in 2022.
References: Timing of Initiation of Oral Anticoagulation after Acute Ischemic Stroke in Patients with Atrial Fibrillation