I don't know all the side effects but I know u need to change your lifestyle if you don't want to get ventricular fibrillation or even a stroke. All those are deadly. Eat healthy, cut back on greasy food and exercise!
There are essentially no side effects to cardioversion. It's a very simple procedure that takes just a few minutes. there is a much higher risk of throwing off blood clots to people who stay in atrial fibrillation.