Well, if the patient doesn't want anticoagulation and never did, I don't know where the dilemma is. He knew the risk of stroke without being anticoagulated, and then had a stroke. What's the point in antiocoagulating now? The stroke is done and irreversible. It seems like a good question for a neurologist, but realistically what difference would it make for you to anticoagulate for the hour or two you've got the patient in the ED? Afib has what, a 1% stroke risk per year, and he already had his stroke? So are you going to run a heparin drip for the next 1 yr, to prevent the next one, considering the clot's already been thrown? Obviously not.
The only effective plan would be to find a time machine (which I imagine would be very expensive) and go back in time 25 years and convince this person to take Coumadin, but unfortunately that's not in your cost-conscious CEOs hospital budget, as classic Deloreans are super expensive, not to mention a working flux capacitor. Otherwise, I don't think it would make a difference what you do. Ischemic CVA outside of tPA window? Aspirin, maybe treat an elevated blood pressure (controversial; argue back and forth, lower BP? how much? how fast? answer depends on the year in which you're asking the question, could change next year) and admit to a neurologist, none of which are going to make one bit of difference in the outcome, either. Would a heparin drip acutely change the outcome? I seriously doubt it. Six months of rehab, might help, 5% or so.
Don't beat yourself up over this one.