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Effects of Omega-3 Fatty Acids on Heart Rate in Cardiac Transplant Recipients

https://doi.org/10.1016/j.amjcard.2006.06.033Get rights and content

Omega-3 fatty acid (n-3 FA) consumption has been linked to reductions in the risk of death from coronary heart disease and, recently, to lower heart rates (HRs). The investigators previously observed a reduction of 5 beats/min in HR in patients with coronary heart disease given n-3 FAs (eicosapentaenoic acid and docosahexaenoic acid) for 4 months. Reductions in HR may be explained by enhanced vagal tone, influences on cardiac voltage-gated ion channels, or both. The hypothesis that n-3 FAs would affect HR independent of vagal input was investigated by studying the effects of n-3 FA supplementation on HR in patients with denervated hearts after orthotopic heart transplantation. Electrocardiographic data obtained in 2 prospective trials in which 18 heart transplant recipients received n-3 FA supplementation (1 to 3.4 g/day) for 4 to 6 months were collected. Patients were studied 4.4 ± 2.6 years after transplantation. HR, QRS complex, and QTc duration were determined before and after treatment. Pretreatment HR was reduced from 88 ± 14 to 83 ± 13 beats/min after n-3 FA treatment (p = 0.016). QRS duration increased from 107 ± 24 to 117 ± 25 ms (p = 0.001). QTc duration remained unchanged from baseline (427 ± 34 ms) to study end (424 ± 39 ms). In conclusion, n-3 FA supplementation reduced HR and prolonged QRS duration in heart transplant recipients who were presumably devoid of vagal innervation. These findings suggest that n-3 FAs may modify electrophysiologic properties of the myocardium itself.

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Methods and Results

We recruited cardiac transplant recipients into 2 separate prospective n-3 FA supplementation studies performed at Mid America Heart Institute Transplant Clinic from 1997 and 2002. In the first study, 27 patients were randomized to 4 capsules/day of a corn oil placebo or Omacor (Reliant Pharmaceuticals, LLC, Liberty Corner, New Jersey). Each capsule of Omacor contained 0.45-g eicosapentaenoic acid (EPA) and 0.39-g docosahexaenoic acid (DHA), for a total daily intake of EPA plus DHA 3.4 g/day.

Discussion

In an earlier randomized, double-blind, crossover study with patients with coronary artery disease and low ejection fractions, n-3 FA supplementation decreased mean HR by about 5 beats/min.8 A recent meta-analysis also concluded that fish oil consumption can reduce HR.9 There are ≥2 possible explanations for this finding, one cardiogenic and the other neurogenic. The former refers to changes in the myocardium itself and the latter to changes in cardiac autonomic control, with a shift toward

Acknowledgment

We wish to acknowledge the invaluable contribution of Kathy St. Clair, RN, for her assistance in this study.

References (19)

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This study was supported by a grant from the Saint Luke’s Hospital Foundation, Kansas City, Missouri.

Disclaimer: Saint Luke’s Hospital holds a minority interest in OmegaMetrix, LLC, Kansas City, Missouri, a company offering blood omega-3 fatty acid testing.

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