I have "mild" A-fib. Translation, while my arrhythmia always shows up on an EKG, I have no conscious symptoms other than relatively light heart beats that I usually see on my blood pressure meter interspersed between regular (for me) heart beats. Even so, one day six years ago (almost to the day) I developed a small blood clot that invaded my brain and caused a "small stroke." That happened although I was taking an anticoagulant (Warfarin) to prevent it. For some reason the drug had an excessive effect (probably the result of a surprise dose of Vitamin K in a meal) and, working with my medical team, I skipped two daily doses of Warfarin, bringing my INR back down where it belonged. Unfortunately, the clot formed and struck me during a long walk. An MRI a short time later confirmed a small clot in a capillary deep in my brain. The stroke effects have not been disabling, just a little inconveniencing in taste, smell, and hearing. I continued bowling the last six years, averaging about 170 per game as usual for the last 60 years.