Aspirin should be added to this patient's medication regimen. She has had an acute ischemic stroke and has atrial fibrillation. No other obvious causes of stroke are present, and she is beyond the treatment window for recombinant tissue plasminogen activator therapy. According to two large clinical trials, aspirin administered within 48 hours of ischemic stroke onset modestly reduces the risk of recurrent ischemic stroke within the first 2 weeks without significantly increasing the risk of intracerebral hemorrhage. Administration of aspirin no later than the end of the second day after a stroke is an accepted quality-of-care core metric in primary and comprehensive stroke centers.

Anticoagulation with warfarin or a newer anticoagulant, such as dabigatran, is required to manage this patient's long-term risk of cardioembolic stroke. Some experts will initiate warfarin within 24 hours of stroke onset in medically stable patients with a small infarction, but withholding anticoagulation for 4 days to 2 weeks is typically recommended for patients with moderate to large infarctions. Until that time, patients are managed with aspirin.

In the acute ischemic stroke setting, intravenous heparin was ineffective compared with aspirin in patients with cardioembolic stroke in a randomized clinical trial. Furthermore, this patient's infarct is large enough to be associated with a risk of hemorrhaging into the bed of the infarct within the first 2 weeks of stroke.