Fish Oil for Secondary Prevention of Atrial Fibrillation
Should We Still Believe in Its Antiarrhythmic Effect?
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- atrial fibrillation
- secondary prevention
- fish oil
- polyunsaturated fatty acids
Several epidemiological and large randomized, clinical trials carried out in the general population and in patients with cardiovascular disease have reported a significantly lower incidence of sudden cardiac death (presumably arrhythmic) with high dietary fish consumption or omega-3 polyunsaturated fatty acid (PUFA) supplements.1 This has prompted interest in exploring the antiarrhythmic potential of PUFAs in patients at particularly high risk of sudden arrhythmic death (ie, patients with internal cardioverter-defibrillators for secondary prevention), but the results were unexpectedly disappointing: the meta-analysis of the controlled studies failed to show any benefit from treatment with PUFAs.2 At about the same time, a proof-of-concept open-label study demonstrated a remarkable 65% reduction in the occurrence of atrial fibrillation (AF) after coronary artery bypass grafting surgery,3 and the search for antiarrhythmic activity of PUFAs in atrial tachyarrhythmias has begun.
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Various animal models of AF, including atrial pacing, simultaneous atrioventricular pacing, vagal stimulation, cardiac surgery and sterile pericarditis, and congestive heart failure induced by ventricular tachypacing or intracoronary infusion of doxorubicin, have been used to demonstrate the effects of PUFAs on electric and structural atrial remodeling.4 In these experiments, treatment with PUFAs prevented significant shortening of the atrial effective refractory period associated with AF, reduced inducibility of AF and duration of induced AF, and attenuated atrial fibrosis although a difference in response was noted in some models (eg, lack of effect in atrial tachypacing was reported).5
Results in the clinical arena have been less consistent. Although an early open-label and a larger observational study reported a reduction in the incidence of postoperative AF,3 3 subsequent trials with a more rigorous design (double-blind, placebo-controlled) did not reproduce these results.6 Similarly, in several epidemiological analyses, high dietary-fish consumption conferred no benefit on the prevention of AF in the …