High-dose omega-3 does not appear
to reduce recurrence of atrial fibrillation
Although some data have suggested that omega-3 fatty
acid supplements, such as from fish oil, may improve treatment of atrial fibrillation,
a randomized trial with more than 600 patients finds that treatment with high-dose
prescription omega-3 did not reduce the recurrence of atrial fibrillation over
six months, according to a study that will appear in the December 1 issue of JAMA.
The study is being released early online because it was presented as a Late Breaking
Clinical Trial at the American Heart Association's 2010 annual meeting.
"Atrial fibrillation (AF) is a highly prevalent disease that is responsible
for reduced quality of life, costly hospitalizations, heart failure, stroke, and
death. No current therapy, drug, device, or ablation is uniformly effective, and
several available therapies have the potential to cause harm. Consequently, useful
alternatives are being sought," the authors write. "Limited data from
small trials suggest omega-3 polyunsaturated fatty acids may provide a safe, effective
treatment option for AF participants."
Peter R. Kowey, M.D., of the Lankenau Institute for Medical Research, Wynnewood,
Pa., and colleagues conducted a randomized clinical trial to assess the efficacy
of a pure prescription formulation of omega-3 fatty acids (prescription omega-3),
at a dose considerably higher than what has been tested in previous trials, for
preventing recurrent atrial fibrillation. The study included 663 U.S. outpatient
participants with confirmed symptomatic paroxysmal (sudden attacks) (n = 542)
or persistent (n = 121) AF, with no substantial structural heart disease, who
were recruited from November 2006 to July 2009 (final follow-up was January 2010).
Participants received prescription omega-3 (8 grams/day) or placebo for the first
7 days; prescription omega-3 (4 grams/day) or placebo thereafter through week
24.
After 6 months of follow-up, the researchers found that in the paroxysmal group,
there were 129 documented symptomatic AF or flutter (abnormal, rapid heart beat)
events (48 percent) in the placebo group and 135 (52 percent) in the prescription
group. In the persistent AF group, there were 18 documented symptomatic AF or
flutter events (33 percent) in the placebo group and 32 (50 percent) in the prescription
group, while in the 2 groups combined there were 147 events (46 percent) in the
placebo group and 167 (52 percent) in the prescription group.
None of the secondary efficacy end points, including first recurrence of AF
or flutter in the persistent group and both groups combined, reached statistical
significance. Sixteen participants (5 percent) taking placebo, and 12 (4 percent)
taking prescription omega-3 discontinued study medication due to an adverse event.
"In this population of patients with symptomatic paroxysmal AF or persistent
AF, and no evidence of substantial structural heart disease, prescription omega-3
did not show evidence of reducing the recurrence of symptomatic atrial fibrillation,"
the authors write.
They add that several factors might contribute to the discordance between their
findings and those of other studies. "Either the positive results reported
in some trials represent a chance effect of small sample sizes or the differences
are real. If the latter, there are several possibilities, including differences
in the study populations, in population-specific AF mechanisms, in dosing regimens
and product formulations, or in concomitant therapies. In our study, nearly half
the events occurred during the first 2 weeks of follow-up, suggesting that fish
oil may not have rapid effects, even with high-loading doses."
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