doi: 10.1161/01.CIR.0000153849.18138.7C
(Circulation. 2005;111:e37.)
© 2005 American Heart Association, Inc.
Correspondence |
Letter Regarding Article by Mozaffarian et al, "Fish Intake and Risk of Incident Atrial Fibrillation"
Department of Nephrology, Aalborg Hospital, Aarhus University Hospital, Aalborg, Denmark, jhc{at}dadlnet.dk
Department of Cardiology, Aalborg Hospital, Aarhus University Hospital, Aalborg, Denmark
Center for Sensory-Motor Interaction, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
The beneficial effect of fish oils on sudden cardiac death is well recognized and is believed to be due to an antiarrhythmic effect of the long-chained n-3 fatty acids in fish oils.1 Therefore, it is of major interest that Mozaffarian and colleagues now report that fish intake might reduce the incidence of atrial fibrillation (AF).2 Although this prospective study does not prove causality between fish intake and the incidence of AF, it is reasonable to mention biologically plausible mechanisms that could explain the effect. However, several of the mechanisms referred to in the paper are based on experimental nonhuman studies; therefore, we would like to add another possible effect of fish oil in humans, which could partly explain the results.
Autonomic influences on the heart have been recognized for many years. Many studies have focused on the modulation of vagal and sympathetic activity related to the onset of AF, and it is now realized that autonomic influences play an important role in the initiation of AF.3 Thus, it has been suggested that AF occurring during daytime is related to an increased sympathetic activity, whereas AF onset during the night is caused by vagal predominance.3
Autonomic tone in humans can be evaluated noninvasively by measuring heart rate variability (HRV) and, interestingly, HRV changes before the onset of AF.3,4 We have extensively examined the effect of n-3 fatty acids on 24-hour HRV in different human populations, and our results clearly show that intake of n-3 fatty acids beneficially modulates cardiac autonomic tone.5,6 This may partly explain a possible beneficial effect of fish oils on the risk of AF, and further studies are needed to validate this hypothesis.
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 Top References References |
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1. Kris-Etherton PM, Harris WS, Appel LJ, American Heart Association. Nutrition Committee. Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease. Circulation. 2002; 106: 2747–2757.
2. Mozaffarian D, Psaty BM, Rimm EB, Lemaitre RN, Burke GL, Lyles MF, Lefkowitz D, Siscovick DS. Fish intake and risk of incident atrial fibrillation. Circulation. 2004; 110: 368–373.
3. Maisel WH. Autonomic modulation preceding the onset of atrial fibrillation. J Am Coll Cardiol. 2003; 42: 1269–1270.
4. Zimmermann M. Autonomic tone and atrial fibrillation. J Cardiovasc Electrophysiol. 2003; 14: 565–566.[CrossRef][Medline] [Order article via Infotrieve]
5. Christensen JH. n-3 fatty acids and the risk of sudden cardiac death. Emphasis on heart rate variability. Dan Med Bull. 2003; 50: 347–367.[Medline] [Order article via Infotrieve]
6. Bigger JT Jr, El Sherif T. Polyunsaturated fatty acids and cardiovascular events: a fish tale. Circulation. 2001; 103: 623–625.
Response
Channing Laboratory, Brigham and Women’s Hospital and Harvard Medical School, Departments of Epidemiology and Nutrition, Harvard School of Public Health, Boston, Mass, dmozaffa{at}hsph.harvard.edu
Cardiovascular Health Research Unit, Departments of Medicine and Epidemiology, University of Washington, Seattle, Wash
Cardiovascular Health Research Unit, Department of Medicine, University of Washington, Seattle, Wash
Department of Public Health Sciences, Wake Forest University School of Medicine, Winston-Salem, NC
Department of Medicine, Wake Forest University School of Medicine, Winston-Salem, NC
Department of Neurology, Wake Forest University School of Medicine, Winston-Salem, NC
Dr Christensen et al bring attention to another important possible mechanism—effects on autonomic tone—that could in part account for a potentially protective effect of fatty fish intake on the incidence of atrial fibrillation (AF). Fluctuations in autonomic tone appear particularly important for lone AF or paroxysmal AF.1,2 However, these relations may differ in the setting of structural heart disease or age-related diastolic dysfunction, when abnormalities of heart rate variability and higher risk of AF may both be consequences of underlying cardiac pathology. Further study is required to determine the causal contribution of autonomic dysfunction to incidence of AF in such individuals, who may comprise the majority of older persons with chronic AF. On the other hand, beneficial effects of fish oil on blood pressure, vascular responses, and left ventricular diastolic function—seen in both animal and human studies3–5—could also in part be a consequence of effects on autonomic function. We agree with the potentially important role of autonomic function in the pathogenesis of AF and the need for further studies to evaluate the interplay between fish intake, autonomic function, and risk of AF.
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TopReferencesReferences |
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1. Andresen D, Bruggemann T. Heart rate variability preceding onset of atrial fibrillation. J Cardiovasc Electrophysiol. 1998; 9: S26–S29.[Medline] [Order article via Infotrieve]
2. Zimmermann M. Autonomic tone and atrial fibrillation. J Cardiovasc Electrophysiol. 2003; 14: 565–566.[CrossRef][Medline] [Order article via Infotrieve]
3. McLennan PL, Barnden LR, Bridle TM, Abeywardena MY, Charnock JS. Dietary fat modulation of left ventricular EF in the marmoset due to enhanced filling. Cardiovasc Res. 1992; 26: 871–877.
4. Geleijnse JM, Giltay EJ, Grobbee DE, Donders AR, Kok FJ. Blood pressure response to fish oil supplementation-metaregression analysis of randomized trials. J Hypertens. 2002; 20: 1493–1499.[CrossRef][Medline] [Order article via Infotrieve]
5. Grimsgaard S, Bonaa KH, Hansen JB, Myhre ES. Effects of highly purified EPA and DHA on hemodynamics in humans. Am J Clin Nutr. 1998; 68: 52–59.[Abstract]
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