Those who suffered only short bouts of atrial fibrillation -- estimated at 20 seconds or less -- were at no more risk for stroke or other heart complications than people without atrial fibrillation, the researchers found.
"Some patients have atrial fibrillation 100 percent of the time, while others might have only a few seconds of atrial fibrillation once a year," explained study author Dr. Steven Swiryn. He's a clinical professor of cardiology at the Feinberg School of Medicine at Northwestern University in Chicago.
"Where atrial fibrillation only happens rarely and lasts a short time, it can be difficult to detect," Swiryn said.
Implanted devices such as pacemakers and defibrillators monitor a patient's heart rhythm constantly, and they can spot short episodes of atrial fibrillation, he said.
"We can then more accurately answer the question, 'How much atrial fibrillation does the patient have to have in order to be at risk of stroke and benefit from anticoagulation [blood thinners]?' " Swiryn said.
The answer seems to be that patients with only short episodes of atrial fibrillation aren't at enough risk for a stroke to warrant blood thinners, he said.
"This allows physicians to avoid prescribing anticoagulation unnecessarily, since the risk of bleeding may be more than the benefit of stroke prevention," Swiryn said.
One heart expert agreed.
"Short episodes of atrial fibrillation that typically last 15 to 20 seconds are really low risk and that should not trigger the use of anticoagulants," said Dr. Nicholas Skipitaris, director of cardiac electrophysiology at Lenox Hill Hospital in New York City.
But starting a patient on a blood thinner also depends on several factors, not just the length of episodes of atrial fibrillation, Skipitaris added. These include the patient's age, gender and whether they have other conditions such as heart failure, high blood pressure or diabetes.
And another heart expert added another caveat.
"More frequent episodes, of even short duration, of atrial fibrillation might still be a concerning development," said Dr. David Friedman. He is chief of heart failure services at Northwell Health Long Island Jewish Valley Stream Hospital in Valley Stream, N.Y.
"Much in the same way as one high blood pressure reading does not automatically mean someone has hypertension, the decision needs to be sorted out with trends over a period of time," he added.
Atrial fibrillation is the most common abnormal heart rhythm condition, and affects about 2.7 million Americans. People who have prolonged episodes of atrial fibrillation have an increased risk for heart complications and stroke. Guidelines recommend that patients with atrial fibrillation take blood thinners to reduce their stroke risk, Swiryn said.
For the study, Swiryn and his colleagues looked at 37,000 EKGs -- a test that graphs heart rhythms -- from more than 5,000 patients over two years. All the participants took part in the RATE Registry, an ongoing study that follows patients with pacemakers or defibrillators.
While those with long episodes of atrial fibrillation were more likely to be hospitalized or die than those without the condition, those with short episodes were not, the study found.
The report was published Oct. 17 in the journal Circulation.
For more information on atrial fibrillation, visit the American Heart Association.
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