Fish Oil and Arrhythmias, Cardiac Arrest

Atrial Fibrillation Recurrence and Fish Oil

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 (atrial fibrillation) 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%.

Preventing AF Recurrence is not Included in the Many Benefits of Fish Oil

Now a group of university-associated American cardiologists reports that prescription omega-3 fatty acid esters (Lovaza) is ineffective in preventing atrial fibrillation 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 atrial fibrillation 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

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