Antiarrhythmic Properties of Fish Oils

CHIETI, ITALY. Several large clinical trials have confirmed the ability of fish oils to prevent sudden cardiac death in both presumably healthy subjects as well as in patients having suffered a heart attack (myocardial infarction).

Researchers at the universities of Chieti and Pisa recently published a review of the current “state-of-the- art” in regard to fish oils and arrhythmias. Highlights are:

• Supplementation with fish oils shows its beneficial effect within a few weeks.
• It is unlikely that the biological effects of fish oils would vary depending on source (oily fish or fish oil supplement).
• Animal experiments have shown that fish oils act on individual myocytes (heart cells) to inhibit the excitatory Na+ current, stabilize the inactivated state of the Na channel, and prolong the effective refractory period of the cardiac cycle. The L-type Ca++ current is also inhibited by fish oils and the outward flow of K+ is reduced. All effects which would reduce the tendency to arrhythmia either by decreasing automaticity or by interfering with re-entry circuits.
• Two small trials have shown a reduction in PVCs (premature ventricular complexes) with fish oil supplementation. In one of these trials 34 participants with frequent PVCs, but no life-threatening arrhythmias were given 2.4 grams/day of fish oils while the control group was given sunflower seed oil which is rich in linoleic acid (an omega-6 fatty acid). PVCs decreased by 48% in the fish oil group as compared to 25% in the sunflower seed group.
• Fish oils have been shown to decrease heart rate variability and there is some suggestion that they may also reduce sympathetic and increase parasympathetic (vagal) activity in the autonomic nervous system.
• Prostaglandins and thromboxane A2, produced from arachidonic acid, are mostly proarrhythmic so a high intake of omega-6 fatty acids may be detrimental.

Although most research, so far, has focused on the effect of fish oil on life-threatening ventricular arrhythmias it is likely than many of the findings may also be applicable to atrial fibrillation.