I'm sorry to ask a profound question but what exactly is fish oil? Is it an antiarrhythmic or is it a cholesterol drug?

The word on the street is that patients who take fish oil have better cardiac outcomes not because of the effects on cholesterol or triglycerides but because of prevention of cardiac arrhythmias.  But in 2008 a meta-analysis came out in BMJ that throws cold water on that concept at least in retrospective studies.

A prospective study OMEGA is evidently finished recruiting and hopefully will publish soon.

A common irregular and often rapid heart rhythm is known as atrial fibrillation or A Fib. Roughly 2.2 million Americans are suffering from some form of heart rhythm disorder. In atrial fibrillation the heart's two small upper chambers (the atria) vibrate irregularly instead of beating effectively. Blood is also not pumped fully out of them so it may clot more readily. A patient can suffer a stroke if a fragment of clotted blood in the atria leaves the heart and lodges in an artery in the brain. Doctors have known for years about the link between atrial fibrillation and strokes.