I’ve been taking Flecainide for over 10 years now, for A fib, and have had no side effects. It keeps me in a normal sinus rhythm most of the time, with rare bursts of A fib which only last for a few minutes, and automatically revert back to normal sinus rhythm. Before Flecainide I had frequent bouts lasting over 30 to 40 minutes at rates of over 190 bpm.