There are two types of strokes: ischemic strokes cause by blood clots or other mechanical blockages (arterial narrowing like in the heart, fat emboli, calcium deposits, etc.), and hemorrhagic strokes caused by a ruptured blood vessel. It is the latter that can cause the worst strokes that result in significant deficits.

If you are cleared of a-fib and your doctor is comfortable putting you on an aspirin regimen and nothing else, then your risk should be about the same as anyone else. Exercise is a great way to prevent clots from forming (if you threw a clot through a PFO then it likely started as a deep vein thrombosis in your leg) and walking would be a very healthy way for you to prevent clots from forming. When this happened had you been sedentary for a while?

MNS