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.