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Hold the Fish Oil for Patients with ICDs

Fish-oil supplements did not reduce the risk for ventricular arrhythmias in patients with implantable cardioverter-defibrillators and, in some ICD patients, increased the risk.

Evidence from epidemiologic and clinical studies suggests that omega-3 polyunsaturated fatty acids (PUFAs) have antiarrhythmic properties and might help to prevent atrial fibrillation and sudden cardiac death. Do PUFAs have an antiarrhythmic effect in patients with histories of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) and implantable cardioverter-defibrillators (ICDs)?

In a multicenter study funded partly by a maker of fish-oil supplements, 200 patients with ICDs (and pre-ICD VT or VF, or recent ICD discharge for VT or VF) were randomized, in double-blind fashion, to receive fish oil (1.8 g/day) or placebo. The subjects' mean LV ejection fraction was 35%. Median follow-up was 24 months.

Mean PUFA levels in red-blood-cell membranes, expressed as a percentage of total fatty acids, increased significantly in the fish-oil group (from 4.7% to 8.3%) but not in the placebo group. At 6, 12, and 24 months, the incidence of ICD discharge for VT/VF did not differ significantly between the groups. Among the 133 patients with previous VT, fish-oil recipients had a significantly higher incidence of ICD discharge than did placebo recipients.

Comment: These findings differ sharply from the considerable evidence suggesting that PUFAs have antiarrhythmic properties, perhaps because this study used ICD discharge (rather than sudden death) as its primary endpoint. Typically, ICD discharges are caused by sustained VT, and sudden death by VF. PUFAs' antiarrhythmic benefits might be greatest in patients with ischemic heart disease and preserved LV function, who tend to experience VF rather than VT (VT is often caused by myocardial reentry).

— Hugh Calkins, MD

Published in Journal Watch Cardiology July 22, 2005

Citation(s):

Raitt MH et al. Fish oil supplementation and risk of ventricular tachycardia and ventricular fibrillation in patients with implantable defibrillators: A randomized controlled trial. JAMA 2005 Jun 15; 293:2884-91.

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