Does Omega-3 Fish Oil Help Prevent Atrial Fibrillation After Coronary Bypass Surgery?

Atrial fibrillation is a potentially very dangerous irregular heart rhythm in which the atria (the upper chambers of the heart) do not fully contract. Atrial fibrillation can allow blood clots to develop in the atria and move to the ventricles (the lower heart chambers) which could eventually lead to a stroke or pulmonary embolism (a blockage in the main artery of the lungs). It is standard procedure to treat everyone with atrial fibrillation with anti-coagulants, anti-arrhythmic medications, and/or to surgically destroy intra-atrial conduction nerves with an electrical current transmitted through a wire placed in the heart and a trans-venous catheter placed in the arm or leg.

It was exciting to learn that omega-3 fish oil given before and after cardiac surgery was found to prevent the complication of atrial fibrillation by up to 54 percent in one study1 and by 34 percent in another.2 Of course, there are tens of thousands of people with atrial fibrillation that do not need heart surgery, but we hate to see atrial fibrillation happen as a complication of cardiac surgery, which can occur.

In the scientific literature there are many articles in support of the use of omega-3s before and after coronary bypass surgery, and there are also many articles that do not support omega-3 use for atrial fibrillation.3,4 In my opinion there are many issues that need to be addressed to consistently obtain better results in these studies to avoid conflicting data:

1. Of the studies I reviewed not one measured the red blood cell (RBC) membrane levels of both omega-3 and omega-6 fatty acids, nor did they check the omega-6/omega-3 ratio, arachidonic  acid/omega-3 ratio, or the Omega-3 Index. The Omega-3 Index is the percentage of omega-3 over total RBC membrane fats. An Omega-3 Index below 4 percent indicates that heart attacks and heart attack deaths are more likely. It is recommended that the Omega-3 Index be 8 percent or higher.  Dr. William Harris, who developed the test that measures this index states that 12 to 15 percent would be ideal.5 RBC membrane levels of fatty acids give a much better indication of total body levels for at least a 3-month period since RBCs live 3 to 4 months. In contrast, serum levels of omega-3 (and all other fats) only reflect dietary intake of fats over the last few days.

2. Most clinical studies I have reviewed (including these) give everyone the same dose. But one size does not fit all any more than one pair of shoes fits all feet. Dosages should ideally be in mg/kg body weight in divided daily doses that aim to achieve ideal omega-3 levels as detected through RBC membrane testing.

3. The doses in several of the studies that did not support omega-3 therapy for atrial fibrillation were quite low, around 1 gram/day.4

4. There was no consideration of whether the patients were taking omega-3, magnesium, or vitamin D3 supplements (or if they had history of good sun exposure or UVB tanning lamps).

The bottom line is everyone—healthy or otherwise—should have at least an annual Omega-3 Index, an annual vitamin D3 blood test (in the form of 25-OH vitamin D, the stable precursor form), and a RBC magnesium level taken. If these three tests were done and levels were optimized before surgery, the outcomes of atrial fibrillation patients would be even better. This obviously applies not only to atrial fibrillation patients, but to everyone. Take these tests and supplement to optimum levels at least annually or more often if you have health challenges.  In my 30-plus years of doing surgery, the healthier and more nutritionally stable patients generally did better.


  1. Calo L, Bianconi L, Colivicchi F, et al., “N-3 Fatty acids for the prevention of atrial fibrillation after coronary artery bypass surgery: a randomized, controlled trial.” J Am Coll Cardiol. 2005 May 17;45(10):1723-8.
  2. Costanzo S, di Niro V, Castelnuovo A, et al., “Prevention of postoperative atrial fibrillation in open heart surgery patients by preoperative supplementation of n-3 polyunsaturated fatty acids: An updated meta-analysis.” Three-day magnesium administration prevents atrial fibrillation after coronary artery bypass grafting.” Ann Thorac Surg. 2005 Jan;79(1):117-26.
  3. Mozaffarian D, Marchioli R, Macchia A, et al., “Fish oil and postoperative atrial fibrillation: the Omega-3 Fatty Acids for Prevention of Post-operative Atrial Fibrillation (OPERA) randomized trial.” JAMA. 2012 Nov 21;308(19):2001-11.
  4. Macchia A, Grancelli H, Varini S, et al., “Omega-3 fatty acids for the prevention of recurrent symptomatic atrial fibrillation: results of the FORWARD (Randomized Trial to Assess Efficacy of PUFA for the Maintenance of Sinus Rhythm in Persistent Atrial Fibrillation) trial.” J Am Coll Cardiol. 2013 Jan 29;61(4):463-8.
  5. Personal communication with Dr. William Harris.
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