Aspirin therapy for prevention of blood clots is far inferior to Coumadin, but may be appropriate, I understand, if there are no other risk factors - and if the AFib is not chronic.
I take both... yes, while one must avoid aspirin when on Coumadin for the treatment of pain/fever/swelling, in small dose it can be taken for added cardio protection. It affects a different mechanism of the blood than does Coumadin.
On a personal level, again, I have had a cardiologist treat me both ways when I was in NSR. Given I always had a chance, and did, return to AFib one doctor didn't want to take any chances, and kept me on Warfarin.
When I was first diagnoised with a-fib I was put on aspirin. My a-fib only happened occasionaly and I had no other heart related problems. My CHADS SCORE was 0. About a year later my a-fib episodes became more frequent and my heart rate became much higher over 200 during the attacks. My EP told me that I needed to come off the aspirin and start on Coumadin because of the higher heart rate.
I know several people who are in permanent a-fib who are on aspirin because their heart rate isn't over 100 and they have no other heart related problems.
So I think it all depends on how fast your heart rate is when in a-fib and what your CHADS score is. Usually these factors determine if coumadin is preferred over aspirin.
The critical thing to think about is your INR score. If you do a search here you will see several threads on INR and INR testing.
If your a-fib is only occasional you still run a risk of generating a clot. When the atria are not doing their job they do not empty out properly. This plus the turbulence caused by the uncoordinated contractions can lead to the formation of clots. If those clots stay in the atrium in which they form all well and good. If they leave the atrium things can go south in a hurry.
If the clot forms in the right atrium and goes into the ventricle and is expelled, then it will go to the lungs. Google pulmonary embolism. Not a good thing to have. In my case it would likely result in my moving down the street from my folks. They are currently bunking at the National Cemetary at Ft. Sam Houston.
If the clot forms in the left atrium things can get interesting there, too. If the clot is small enough it can go into the coronary arteries. Google coronary thrombosis. Not good. If it makes it into the aorta there is different fun to be had. The first tap off the aorta is the carotid. At that point is heading for your brain and WILL result in an ischemic stroke.
If it misses the carotid it is still going to go somewhere. Eventually it will get to a point that is too small for it to pass. At that point all tissue downstream of that point ceases to receive blood. Not good.
As I said, the important thing is your INR score. If you have a-fib - especially if it becomes chronic - you need to have your INR at a safe level - usually 2.0 - 3.0. Do you get your INR checked? If so how often?
Think about it. Take care.