Some meds to treat afib and high blood pressure, especially calcium channel blockers, cause foot and ankle swelling. I have afib and take (among other meds) cardizem, a calcium channel blocker. It caused edema, which has now been corrected by also taking a diuretic (HTCZ).
I also take coumadin and don't believe edema is a side-effect.
Edema can be a symptom of CHF, but I don't know that it leads to CHF. IIt is not a side effect that I'm aware of with Coumadin, so this is likely due to something else. Definitely give the doctor a call.