by Craig Weatherby
A few small studies have suggested that fish oil might reduce the risk of recurring atrial fibrillation, which doctors abbreviate as A Fib or AF.
A Fib is a type of irregular heartbeat (arrhythmia) that often occurs unnoticed and without immediate consequence… but it may signal underlying cardiovascular disease, and can cause a stroke or, more rarely, death.
What is atrial fibrillation?
The condition doctors call “A Fib” is a common heart rhythm disorder caused by a problem in the conduction of electrical impulses in the upper chambers, or atria, of the heart.
A Fib and other rapid heartbeats can arise in the atria or in the juncture between the atria and the lower chambers (ventricles).
In A Fib, the electrical signals that coordinate the muscle of the upper chambers (atria) of the heart become rapid and disorganized, typically causing the atria to beat faster than 300 beats per minute. (The normal resting heart rate is about 60 to 80 beats per minute).
More than two million people in the U.S. have A Fib, and about 160,000 new cases are diagnosed each year.
A Fib is uncommon among young people, but the likelihood of developing the condition increases as we get older. Between three and five percent of people aged 65 or older have atrial fibrillation, and some nine percent of people age 80 or older have it.
The results of a placebo-controlled clinical trial published in February of 2010 found that omega-3 supplements (two grams per day) given to heart patients about two weeks before they underwent coronary artery bypass surgery did not reduce the risk of atrial fibrillation in the few days following the surgery. (Saravanan P et al. 2010)
That wasn’t very surprising given the short period of time the patients were given omega-3s before going under the knife.
But the results of a much longer, larger clinical trial suggest that high-dose omega-3 fish oil may not reduce the recurrence of A Fib in people diagnosed with it.
What’s up with omega-3s and A Fib?
A Fib is a common condition that can lead to a lower quality of life, costly hospitalizations, heart failure, stroke, and even death.
No current drug, nutrient, device, surgery, or other treatment is proven effective, and several available therapies can cause harm.
As the authors wrote, in explaining why they conducted this trial, “Limited data from small trials suggest omega-3 polyunsaturated fatty acids may provide a safe, effective treatment option for AF...”
Peter Kowey, M.D., of the Lankenau Institute for Medical Research led this randomized, placebo-controlled clinical trial, which was designed to assess the efficacy of omega-3 fish oil at a dose considerably higher than any previously tested.
What the trial did and showed
The study included 663 U.S. outpatient participants with confirmed AF, with no substantial underlying heart disease (Kowey PR et al 2010).
Of the 663 participants, 542 had “paroxysmal” atrial fibrillation, which appears suddenly and resolves on its own, and 121 had “persistent” atrial fibrillation, which needs treatment.
The numbers of paroxysmal A Fib patients in the placebo and treatment groups who had A Fib recurrences were about equal (48 percent and 52 percent, respectively).
The participants received either very-high-dose omega-3s (8 grams per day) or placebo pills for the first seven days, followed by a lower (but still quite high) 4 gram daily omega-3 dose or placebo thereafter through week 24.
After six months, the fish oil showed no benefit – 52 percent of those taking omega-3s experienced recurrences of A Fib, versus 46 percent of the placebo group.
In patients with persistent A Fib, more patients in the omega-3 group had recurrences than in the placebo group (50 percent and 33 percent, respectively).
The doses used in the study were far higher than doses used in previously published in studies.
The authors noted that several factors might explain the difference between their findings and the positive findings from 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 [is true], 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.”
And they went on to make a crucial point that recognizes the difference between nutrients and potent, fast-acting drugs: “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 doses.”
Omega-3s may prevent a far deadlier form of fibrillation
The most common cause of cardiac arrest is a heart rhythm disorder or arrhythmia called ventricular fibrillation (VF).
VF is the usual immediate cause of Sudden Cardiac Death, which accounts for half of all heart-related deaths and often occurs in active, outwardly healthy people with no known heart disease or other health problems.
Fish oil is clinically proven to reduce the risk of Sudden Cardiac Death, making it a rare weapon against a threat that’s significantly less predictable than heart attacks are. (Fish oil is clinically proven to reduce the risk of second, but not first, heart attacks.)
In a healthy heart, its innate electrical “pace-maker” triggers the heartbeat, and then electrical impulses run along pathways in the heart, causing it to contract in a regular, rhythmic way.
When a contraction happens, blood is pumped. But in ventricular fibrillation, the electrical signals that control the pumping of the heart suddenly become rapid and chaotic.
As a result, the lower chambers of the heart, the ventricles, begin to quiver (fibrillate) instead of contract, and they can no longer pump blood from the heart to the rest of the body.
If blood cannot flow to the brain, it becomes starved of oxygen, and the person loses consciousness in seconds.
Unless an emergency shock is delivered to the heart to restore its regular rhythm, using a machine called a defibrillator, death can occur within minutes. It’s estimated that more than 70 percent of ventricular fibrillation victims die before reaching the hospital.
Since omega-3s reduce the risk of Sudden Cardiac Death, it seems plausible to propose that they do it in part by reducing a vulnerable person’s propensity to undergo VF.
However, omega-3s have displayed mixed effects with regard to various kinds of arrhythmia and different classes of patients.
So, as the authors of a recent evidence review wrote, “Additional studies are needed to evaluate the effect of omega-3 fatty acid before it can be routinely recommended for the management of arrhythmia” (Cheng JW, Santoni F 2008).
American Medical Association (AMA). Use of Omega-3 Does Not Appear to Reduce Recurrence of Atrial Fibrillation. November 15, 2010. Accessed at http://pubs.ama-assn.org/media/2010jer/1115.dtl#4
Cheng JW, Santoni F. Omega-3 fatty acid: a role in the management of cardiac arrhythmias? J Altern Complement Med. 2008 Oct;14(8):965-74. Review.
Kowey PR et al. Efficacy and Safety of Prescription Omega-3 Fatty Acids for the Prevention of Recurrent Symptomatic Atrial Fibrillation: A Randomized Controlled Trial. JAMA 2010;304: doi:10.1001/jama.2010.1735. Accessed at http://jama.ama-assn.org/cgi/content/short/jama.2010.1735
Saravanan P, Bridgewater B, West AL, O'Neill SC, Calder PC, Davidson NC. Omega-3 fatty acid supplementation does not reduce risk of atrial fibrillation after coronary artery bypass surgery: a randomized, double-blind, placebo-controlled clinical trial. Circ Arrhythm Electrophysiol. 2010 Feb 1;3(1):46-53. Epub 2009 Dec 30.