People with atrial fibrillation who have a stroke while receiving a DOAC are at increased risk of experiencing another stroke. Physicians do not know the best medication to prevent another stroke in this group of people. Options include continuing the same DOAC, switching to another DOAC or switching to warfarin.

The investigators of the SWITCH-AF trial are trying to find out whether switching to warfarin or continuing a DOAC is better for preventing stroke.

The purpose of this study, called a pilot study, is to test the study plan and to find out whether enough participants will join a larger study that answers the question. A pilot study involves a small number of participants and it is not expected to tell us which treatment is better.

Inclusion Criteria:

1. Written informed consent provided.
2. Age >18 years.
3. Documented history of AF or atrial flutter.
4. Ischemic stroke while on a DOAC within 14 days prior to enrollment identified on imaging.
5. In the opinion of the investigator, it is safe to initiate oral anticoagulation with either a VKA or a DOAC within 24 hours of randomization-

Exclusion Criteria:

1. There is strong evidence for the qualifying stroke event to be associated with permanent discontinuation of DOAC therapy (for any reason)
2. Patient is unable or unwilling to take oral anticoagulation
3. History of intracranial bleeding.
4. Patient is on chronic hemodialysis or likely to need renal replacement therapy during the course of the trial.