Prescription fish oil does not prevent AF recurrence
WYNNEWOOD, PENNSYLVANIA. Fish oils (notably eicosapentaenoic acid and docosahexaenoic acid) have potent electrophysiological, autonomic nervous system modulating, and anti-inflammatory effects in atrial and ventricular tissue. Several trials have shown fish oil consumption to have beneficial effects on heart rate variability and to reduce sudden cardiac death in patients having experienced a heart attack. There is also substantial evidence that fish oil consumption helps reduce inflammation and plays an important role in preventing atherosclerosis, heart attack and ischemic stroke. Several smaller trials have also found that supplementation with from 1 to 1.7 grams/day of natural fish oil reduces AF recurrence in patients having undergone coronary bypass surgery, patients having undergone electrical cardioversion, and those with dual chamber pacemakers. The reduction in AF recurrence rate ranged from about 30% to about 60%.

Now a group of university-associated American cardiologists reports that prescription omega-3 fatty acid esters (Lovaza) is ineffective in preventing AF recurrence in paroxysmal and persistent afibbers. Their 6-month trial included 663 afibbers with confirmed paroxysmal (n=542) or persistent (n=121) AF and no substantial structural heart disease at time of enrolment from November 2006 to July 2009. The average age of the participants was 60 years, 56% were male, 90% were white Caucasians, and a large proportion of the group were obese (average BMI of 30.7). Almost half of the entire group (45%) were on statin drugs, 13% were taking an antiarrhythmic, and 39% were on ACE inhibitors or angiotensin II receptor blockers. All patients were in normal sinus rhythm at enrolment.

After randomization, study participants were assigned to receive a placebo (corn oil) or Lovaza. Each 1-gram capsule of Lovaza contained approximately 465 mg of eicosapentaenoic acid and 375 mg of docosahexaenoic acid. Dosage was 8 grams/day of Lovaza or corn oil (placebo) for the first 7 days and then 4 grams/day thereafter through week 24.

At the end of 24 weeks, 48% of the paroxysmal afibbers in the placebo group had experienced one or more documented symptomatic atrial flutter or atrial fibrillation events. The corresponding number in the Lovaza group was 52%. In the persistent AF group, 33% of the placebo group experienced event(s) versus 50% in the Lovaza group. None of these differences were statistically significant. The researchers noted that the average heart rate during an episode was about 7 bpm lower in the Lovaza group than in the placebo group. They also observed an 11.5% larger drop in triglyceride levels and an 11.4% larger drop in the level of very low-density lipoprotein in the Lovaza group as compared to the placebo group at the end of the 24-week trial period.

Of particular interest is their comment that nearly half of the AF and flutter events occurred during the first 2 weeks of follow-up, suggesting that the effect of fish oil supplementation may not have rapid effects, even with high-loading doses. They conclude that Lovaza does not reduce recurrence rate among paroxysmal afibbers when given for a period of 24 weeks.

Kowey, PR, et al. Efficacy and safety of prescription omega-3 fatty acids for the prevention of recurrent symptomatic atrial fibrillation. Journal of the American Medical Association, Vol. 304, No. 21, December 1, 2010, pp. 2363-72

Editor's comment: First it should be kept in mind that Lovaza is a synthetic product formed by reacting fish oils (eicosapentaenoic acid and docosahexaenoic acid) with ethyl alcohol to form omega-3-acid ethyl esters. It is by no means certain that the ester of an acid will have the same properties as the acid itself. A good example is nitroglycerine, which has very different properties from its parent compounds – nitric acid and glycerine. Thus it may well be that eicosapentaenoic acid may behave quite differently from its ethyl ester. The fact that at least half a dozen studies have shown a beneficial effect of fish oils on atrial fibrillation recurrence (fish oil studies) would tend to support the idea that fish oils can be effective in preventing AF, whereas Lovaza obviously is not. It should also be noted that the triglyceride-lowering effect of Lovaza is not superior to that of pharmaceutical grade, natural, unmodified fish oil.