Joe: Have you tried the exogenous Calcium reduction idea, where you cut way down on dietary Ca+, and boost Vit D3 levels to help the body process existing levels of Ca+ into the bones? Steve Karr and GeorgeN have discussed this. For me, after I implemented the Ca+ reduction protocol, my Vagal response seems diminished. My HR does not not drop nearly as fast as it used to after activity. I do not know the precise biological mechanism involved.
In this video, at the the 2:25 mark, the EP says that the dual activation of both the sympathetic and parasympathetic nervous system causes to much Ca+ to be released into the cell, and that this initiates AFIB.