I checked the websites that I believe are credible. They say that the caffeine or other substances in chiocolate are unlikely to cause afib. However, I am allergic to chocolate. I went to an allergist who discovered it. I avoid chocolate. If I have chocolate, I almost always get scintillating scotoma (visual aura associated with migraine) also known as silent migraine or occular migraine. So anyway, I googled allergy and the below came up:

Role for Immune Cells Known as Mast Cells in Atrial Fibrillation
Science Daily (Dec. 23, 2009) Atrial fibrillation (Afib) is the most common type of abnormal heart beat. It is characterized by scarring of the atrial region of the heart (a hallmark known as atrial fibrosis). Although atrial fibrosis is thought to perpetuate Afib, exactly how it develops has not been determined. Some research has suggested a role for inflammation in the process.
Consistent with this, a team of researchers led by Issei Komuro, at Chiba University Graduate School of Medicine, Japan, has now identified a role for immune cells known as mast cells in inducing atrial fibrosis and Afib in a mouse model of the condition.
The research appears in the Journal of Clinical Investigation.
Initial analysis indicated that in the mouse model of Afib, mast cells accumulate and become activated in the atria of the hearts, which are characterized by atrial fibrosis and enhanced susceptibility to induction of Afib. Stabilizing mast cells and generating mast cell-deficient mice reduced fibrotic atrial remodeling and susceptibility to Afib induction. Mechanistic studies determined that atrium-infiltrating mast cells increased production of the molecule PDGF-A and that this promoted atrial fibrosis and susceptibility to Afib induction.
The authors therefore suggest that targeting the mast cell/PDGF-A axis might provide a way to prevent Afib in stressed hearts, although they caution that further studies are needed to determine whether the same mechanism operates upstream of Afib in large animals.


petey

Linking mast cells with allergy:

A mast cell (also known as mastocyte and labrocyte is a resident cell of several types of tissues and contains many granules rich in histamine and heparin. Although best known for their role in allergy and anaphylaxis, mast cells play an important protective role as well, being intimately involved in wound healing and defense against pathogens.

I'm a chocoholic. I would inject Hershey Syrup into my veins if I could :)
Chocolate does not trigger my afib. I found that lack of sleep and/or stress are my main triggers.

Chocolate calms me down. It's my drug of choice. :)

Chocolate, in vast quantities, has triggered a-fib for me. Unfortunately, chocolate and moderation do NOT belong in the same sentence for me.

I have half a block of dark chocolate each night and it has not caused afib for me.
Moy...

This is from Wikipedia..

Chocolate may be a mild stimulant to humans mainly due to the presence of theobromine.[37] It is much more potent for horses, and its use in horse racing is prohibited.
White chocolate contains only trace amounts of the caffeine and theobromine of normal chocolates, because these chemicals are contained in the cocoa solids, not the cocoa butter, from which white chocolate is made.

Since the theobromine has a stimulant effect it could be a trigger. A fib is very tricky though. Sometimes I think something is a trigger, but on another occasion I don't have a problem. Usually I have to try something a few times to decide if it is something I should avoid.

My experience as well. I have had afib after a chocolate bar..or 2. But only once. I am careful now, not to overindulge.

I drink decaf since being diagnosed.

Wine is a trigger for me. Only a few times have I been able to enjoy it w/o a fib. I stay away from it completely now. (gentle sob)

I generally try to avoid chocolate because it makes me antsy. And antsy is the enemy of a normal heart rhythm.

But that's a drag because dark chocolate is a good natural treatment for high blood pressure. And it's so darn good. Bummer.