Study Indicates Fish Oil Supplements Do Not Lower Risk of Serious Heart
Rhythm Problems for Patients with Implantable Defibrillators

CHICAGO - Even though previous research has shown that fatty acids from
fish oil reduce the risk of sudden cardiac death, patients with
implantable defibrillators who took fish oil supplements did not see a
reduction in serious heart rhythm abnormalities, according to a study
in the June 15 issue of JAMA.

Since the original observations that Greenland Eskimos eating a diet
high in omega-3 polyunsaturated fats (PUFAs) from sea mammals and fish
had an unexpectedly low risk of cardiac death, multiple lines of
evidence have suggested that omega-3 PUFAs have antiarrhythmic
properties, according to background information in the article. Several
clinical trials have shown that dietary changes or supplements to
increase omega-3 PUFA intake result in a reduced risk of sudden death
without a consistent change in risk of heart attack.

Merritt H. Raitt, M.D., of Oregon Health and Science University and the
Portland VA Medical Center, Portland, Ore., and colleagues conducted a
study to determine if fish oil supplements would have antiarrhythmic
properties in patients with a recent episode of sustained ventricular
arrhythmia. The double-blind, placebo-controlled trial was performed at
6 U.S. medical centers with enrollment from February 1999 until January
2003. The study included 200 patients with an implantable cardioverter
defibrillator (ICD) and a recent episode of sustained ventricular
tachycardia (VT) or ventricular fibrillation (VF).  Patients were
randomly assigned to receive fish oil, 1.8 g/d, 72 percent omega-3
PUFAs, or placebo and were followed up for a median of 718 days.

The researchers found that at 6, 12, and 24 months, 46 percent, 51
percent, and 65 percent of patients randomized to receive fish oil had
ICD therapy for VT/VF compared with 36 percent, 41 percent, and 59
percent for patients randomized to receive placebo. In the subset of
133 patients whose qualifying arrhythmia was VT, 61 percent, 66
percent, and 79 percent of patients in the fish oil group had VT/VF at
6, 12, and 24 months compared with 37 percent, 43 percent, and 65
percent of patients in the control group. Recurrent VT/VF events were
more common in patients randomized to receive fish oil.

"This study was undertaken to better understand the previously observed
reduction in sudden death mortality after myocardial infarction
associated with fish oil supplementation. The fact that we were not
able to demonstrate an antiarrhythmic effect of fish oil does not call
into question the potential benefits of fish oil or dietary fish intake
in patients who have had a myocardial infarction. Instead, our results
suggest that the mechanism of benefit, if due to antiarrhythmic
properties, may not be due to the suppression of reentrant VT or VF.
The lack of benefit and the suggestion that fish oil supplementation
may increase the risk of VT or VF in some patients with ICDs can
reasonably be interpreted as evidence that the routine use of fish oil
supplementation in patients with ICDs and recurrent ventricular
arrhythmias should be avoided," the authors conclude.

(JAMA. 2005;293:2884-2891.

Editor's Note: This study was supported by a National Institutes of
Health grant, Public Health Service grant, and Hoffman-LaRoche Inc.