If I might comment on your comment, I only suggested GERD because it's been implicated in AF, and also because based on what little information I had it seemed logical as an etiology for the AF. I hope you will print out my little erroneous analysis and let your cardiologist read it.
About playing your horn, you might want to think about staying below G above the staff for a few months if you want to return to playing sooner than advised. That will attenuate pressure on the diaphragm and abdomen a bit. Just think about Chet Baker. With occasional exceptions he played mostly in the lower register and made memorable music. It could be a good opportunity to explore that avenue for a while.