Fish oil supplements do not
lower risk
of serious heart rhythm problems
Newswise — 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.
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