Every case is different. Certainly mechanical valves are a consideration. I have watched Dr. Natale do atrial fibrillation on people with mechanical valves. Dr. Natale is now in California. If you are near Cleveland or California, consider getting a second opinion from someone like Bob Schweikert at the Cleveland Clinic or Dr. Natale in California. If they say no, it might be time to look into other options. A pacemaker may help but I do not want to comment on whether or not you need one without knowing the whole case. decisions can be difficult sometimes.
I hope this helps, thanks for posting.
http://www.andreanatale.com/