THE OPERA TRIAL: Fish Oil and Postoperative Atrial Fibrillation: The Omega-3 Fatty Acids for Prevention of Post-Operative Atrial Fibrillation Randomized Trial”

The subjects of this double-blind randomized trial were 1,516 patients (mean age 64 years) scheduled to undergo cardiac surgery (valve surgery in approximately 50%). The patients randomly were assigned to receive a preoperative loading dose of 10 g of n-3 PUFAs over 3-5 days (n = 758) or a matching placebo (n = 758). Postoperatively the patients received 2 g/day
until hospital discharge. Electrocardiographic monitoring was performed for ≥5 days. The primary endpoint was postoperative AF lasting ≥30 seconds.
There was not a significant difference in the percentage of patients with postoperative AF between the n-3 PUFA group (30%) and the placebo group (30.7%). There also was not a significant difference in major postoperative cardiovascular events between the two groups (1.7% vs. 2.6% in the n-3 PUFA
and placebo groups, respectively).
The authors concluded that fish oil does not reduce the incidence of AF after cardiac surgery.
Prior studies that investigated the effects of fish oil on postoperative AF and on AF in the ambulatory setting have reported mixed results. However, fish oil consistently did prevent AF in the only two studies in which the patients
were pretreated for 4 weeks before cardioversion. These studies suggested that it takes at least 3-4 weeks for the components of fish oil to become incorporated into cell membranes and to start exerting antiarrhythmic ion channel effects. This may explain why fish oil was not found to have an antiarrhythmic effect in the present study.

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