As an example of these facts, studies in hypertensive rat hearts, which have a higher activity of the enzyme NADPH oxidase implicated in oxidative stress and present high arrhythmic risk, have shown that treatment with melatonin has positive effects, avoiding arrhythmias, either sustained ventricular tachycardia or ventricular fibrillation [18, 198, 229]. Here, FMO5 is linked to ventricular fibrillation.