Omega-3 and Atrial Fibrillation Post-CABG

To the Editor

The recent paper by Heidt et al. [1] took a novel approach to studying the potential inhibitory effect of omega-3 fatty acids on the development of atrial fibrillation (AF) in patients undergoing coronary artery bypass surgery. By using an i. v. emulsion of fish oil (Omegaven), tissue levels could be rapidly increased in a setting where high-dose oral omega-3 supplementation can be difficult to achieve. They reported that the intervention reduced postoperative AF rates by about 50 %, confirming a previous supplementation-based approach reported by Calò et al. [2]. There are, however, several errors and omissions in the report that, if corrected, would help clarify the findings of this interesting study.

Errors include referring to the control i. v. emulsion, which contained soya oil, as providing “saturated free fatty acids.” Soya oil is a triglyceride (not a free fatty acid), and it is rich in the omega-6 polyunsaturated fatty acid linoleic acid (about 50 %) followed by about 20 % oleic acid (mono), with 15 % saturated, and 7 % alpha-linolenic (the short-chain omega-3 PUFA). Secondly, they indicate that “There are several studies which have shown a beneficial effect of PUFA [the fish oil] on elevated LDL plasma levels,” with reference to DART [3], JELIS [4] and a study by Nilsen et al. [5], none of which reported effects of omega-3 (or fish) on LDL‐c. Fish oils lower triglycerides, but not LDL [6].

More disconcerting are the omissions of important data from the paper. In the abstract, they indicate that AF occurred in 15 controls and 9 fish oil-treated patients (p < 0.05), but in the Results section (Table 3) they list 26 controls and 13 fish oil-treated patients who developed AF over the first 3 days, and there is no statistical analysis of these data. They also note in the abstract (without data) that the fish oil group had shorter ICU stays, but there are no data in the Results section on this endpoint. Figures 2 and 3 are enigmatic with no axis titles, no description what the “acceptance and rejection lines” mean, and the equations from which these lines are calculated (in the appendix) are unhelpful since none of the variables are defined.

The study by Heidt et al. may make an important contribution to defining the clinical utility of omega-3 fatty acids in the prevention of AF, but their data need to be fully and properly presented.

References

• 1 Heidt M C, Vician M, Stracke S K et al. Beneficial effects of intravenously administered N-3 fatty acids for the prevention of atrial fibrillation after coronary artery bypass surgery: a prospective randomized study.  Thorac Cardiovasc Surg. 2009;  57 276-280
• 2 Calò 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;  45 1723-1728
• 3 Burr M L, Fehily A M, Gilbert J F et al. Effects of changes in fat, fish, and fibre intakes on death and myocardial reinfarction: diet and reinfarction trial (DART).  Lancet. 1989;  2 757-761
• 4 Yokoyama M, Origasa H, Matsuzaki M et al. Effects of eicosapentaenoic acid on major coronary events in hypercholesterolaemic patients (JELIS): a randomised open-label, blinded endpoint analysis.  Lancet. 2007;  369 1090-1098
• 5 Nilsen D W T, Albrektsen G, Landmark K et al. Effects of a high-dose concentrate of n-3 fatty acids or corn oil introduced early after acute myocardial infarction on serum triacylglycerol and HDL cholesterol.  Am J Clin Nutr. 2001;  74 50-56
• 6 Harris W S. n-3 Fatty acids and serum lipoproteins: human studies.  Am J Clin Nutr. 1997;  65 (Suppl.) 1645S-1654S