Timing of Initiation of Oral Anticoagulation after Acute Ischemic Stroke in Patients with Atrial Fibrillation

Patients with atrial fibrillation (AF) who suffer an acute ischemic stroke are at risk for both hemorrhagic transformation and recurrent ischemic stroke in the acute post-stroke period. Oral anticoagulants are recommended for secondary stroke prevention in patients with AF. The optimal time to initiate anticoagulant therapy after acute ischemic stroke in patients with AF is uncertain. There is concern that early initiation increases the risk of hemorrhagic transformation, whereas delayed initiation leaves the patient at risk for recurrent ischemic stroke. In this article, we provide a review of the risk of hemorrhagic transformation of acute ischemic stroke as well as review the literature and major guidelines addressing the timing of anticoagulation initiation after an acute ischemic stroke in patients with AF. Relevant articles published from 1990 to the present were identified using the PubMed and Embase databases. The majority of available literature is observational data. Large ischemic lesions, cerebral microbleeds, thrombolytic therapy, and other clinical factors may increase the risk of hemorrhagic transformation of an acute ischemic stroke. Parenteral anticoagulation within 48 hours is associated with an increased risk of hemorrhagic transformation and is not recommended. Insufficient data exist to support the safety of routine oral anticoagulant (direct oral anticoagulants or warfarin) initiation within 48 hours of an acute ischemic stroke. Direct oral anticoagulant initiation within 2 days of an acute ischemic stroke is associated with a 5% rate of hemorrhagic transformation. Infarct size and presence of hemorrhage are important factors in identifying the optimal time to initiation and should guide decisions when available. A recommended framework for patient decision making is provided. Randomized controlled trials in this area are needed to identify the optimal timing of anticoagulation initiation, and such trials are under way.