PARKVILLE, VICTORIA, AUSTRALIA. Ectopic beats (heart beats initiated at a location other than the sinoatrial node) originating in the pulmonary veins (PVs) are a prime factor in the initiation and maintenance of paroxysmal atrial fibrillation (PAF). In addition, it is also well established that the PVs of patients with PAF exhibit distinct electrophysiologic properties that may form a substrate for AF maintenance. Long-chain omega-3 polyunsaturated fatty acids, in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the main components of fish oil, have consistently been shown to have anti-fibrillatory effects, but the evidence regarding chronic supplementation with fish oil on the initiation and maintenance of PAF is controversial.

Researchers at the Royal Melbourne Hospital now report the results of a clinical trial carried out to determine the effects on pulmonary veins and left atrium electrophysiology of 1-month (average 40 days) supplementation with a natural fish oil preparation providing a daily intake of 1500 mg of DHA and 300 mg of EPA. The trial involved 36 patients with PAF (18 to 75 years old) who were scheduled to undergo a pulmonary vein isolation (PVI) procedure. At least a month before the PVI the trial participants were randomly assigned to a control group or to the fish oil group.

On the day of the procedure all patients underwent continuous electrocardiographic monitoring for 4 hours before ablation. Blood samples were also drawn to determine fish oil concentration expressed as percent fraction of total fatty acids in the phospholipid fraction. After insertion of the necessary catheters, but prior to the actual ablation, the Australian researchers measured the following electrophysiological parameters. For further explanation see Heart Rhythm 101.

• RR interval � The elapsed time between two heart beats measured in milliseconds
• P wave duration (atrial depolarization)
• Effective refractory periods (ERPs) of each pulmonary vein and left atrium
• Pulmonary vein and left atrium conduction times

There were no significant differences in RR interval, P wave duration, and pulmonary vein and left atrium conduction times between the two groups. However, ERPs in the pulmonary veins and the posterior (back wall) left atrium were significantly longer in the fish oil group. This is very significant as a longer ERP is associated with a lower risk of initiating ectopic beats and AF. The difference in ERP was substantial with all members of the fish oil group having an ERP (in the left and right superior PVs) of 200 ms or longer as compared to the control group where ERPs as short as 120 ms were recorded. The members of the fish oil group also exhibited less dispersion of pulmonary venous refractoriness, which has been associated with a decreased tendency to PAF initiation.

The researchers speculate that the beneficial effects of fish oil may be due to one or both of two mechanisms:

• A decrease in the frequency of AF episodes during the supplementation period resulting in reverse electrical remodeling.
• A beneficial effect of incorporated fish oil on PV cellular membranes.

Kumar, S, Sparks, PB, et al. Effects of chronic omega-3 polyunsaturated fatty acid supplementation on human pulmonary vein and left atrial electrophysiology in paroxysmal atrial fibrillation. American Journal of Cardiology, May 28, 2011 [Epub ahead of print]

Editor�s comment: It is unfortunate that this study did not distinguish between adrenergic and vagal AF as the effect of chronic fish oil supplementation may differ. However, it certainly would seem a worthwhile experiment to try supplementing with a high DHA concentration fish oil for a couple of months to see if episode frequency is affected.