You're probably not going to want to hear this, but there is no "natural" remedy for atrial fibrillation
If you have it, and if you've spoken to your cardiologist about it, then you know what causes it. actually, there is more than one cause for it. In all cases, it's disease of the electrical nodes in the heart, the sinus
node (usually) and/or the AV node. It can be a "reentrant" kind (an extra "circuit" in the nerves of the heart) of extreme tachycardia
or an "ectopic" kind (one or more places other than the SA node where the heartbeat starts), so one remedy, natural or not, wouldn't work on all cases of afib.
The cause is disease, a destruction of the fibers of the node(s) of the heart, and there is no natural remedy for this.
The result eventually will be a pacemaker or death.
Please don't waste time looking for a natural remedy. This is serious. Go to your cardiologist now.