t know much about PAH, but wonder if your doctor has done an echocardiogram of you heart
to get a good measure on it physical condition. In particular if the valves
are working sufficiently.
The only thing I take for AFib is Metoprolol to control my HR, keep it from running too high/fast. I have never taken more than 200 mg a day, and that has given me some problems with dizziness and fatigue. You didn't mention, so I assume you can handle the 250 mg dose level.