Your doctor lowered it to 25 mg Twice Per Day? And he's aware of the symptoms you're having? What is your heart rate now, what was it then? I only developed afib a year ago, I'm surprised how much my heart feels like it's banging around at times but how relatively steady my heart rate is. Afib is known as an Irregularly Irregular heart beat. So the feeling of your heart beat can be irregular.
To give you an example, and I'm talking disorders other than afib, some people have PVCs in a pattern. Bigeminy is a normal beat and a PVC, and so on. Trigeminy is two normal beats and a PVC. These people are Regularly Irregular.
Afib is Irregularly (no pattern) Irregular (not the standard sinus rhythm).
Anyone first experiencing these heart rhythm issues must be assessed by a doctor. Anyone with a known disorder that experiences a change for the worse, or new symptoms, must be assessed by a doctor.
Those of us with heart rhythm disorders should be assessed by a doctor at a frequency usually set by him or her, even if we feel well.