Fish oil fails to hold off heart arrhythmia

CHICAGO — Fish oil, which has shown signs of benefit for the heart, doesn’t seem to help people with atrial fibrillation, the most common type of heart arrhythmia, researchers reported November 15 at a meeting of the American Heart Association.

Atrial fibrillation is a form of heart arrhythmia in which scrambled electrical impulses cause heart muscles to contract abnormally. Diets high in fish have been associated with protection against heart attacks and heart failure, and the omega-3 fatty acids in fish oil had been shown in some studies, but not others, to benefit irregular heartbeat.

In the new study, researchers randomly assigned 527 people with paroxysmal atrial fibrillation to get either high-dose fish oil or a placebo capsule. In these patients, an irregular heart rhythm crops up periodically but returns to normal on its own, said study coauthor Peter Kowey, a cardiologist at the Lankenau Hospital in Wynnewood, Penn. Despite the irregular heartbeat from time to time, he said, “this is a relatively healthy population.”

After six months, about half in each group had a recurrence and there was no clear difference between groups in the number of episodes experienced.  A smaller test comparing patients who had a more persistent form of atrial fibrillation that doesn’t self-correct also showed no apparent benefit from fish oil.

“The fact that this drug failed in this population, in my opinion, makes it highly unlikely  that you would see efficacy in other groups,” Kowey said.

But Christine Albert, a cardiologist at Harvard Medical School and Brigham and Women’s Hospital in Boston, said that further study will be needed, particularly since past results have been mixed and this trial lasted only six months. “There may be different effects in different populations,” she said, “and some of these effects might take time.”