Short Bouts of AF May Not Require Anticoagulant Treatment

A large registry study has found that short bouts of atrial fibrillation (AF) are not associated with any adverse events and, therefore, may not require anticoagulation or any other treatment.

The RATE Registry (Registry of Atrial Tachycardia and Atrial Fibrillation Episodes) enrolled 3,141 patients with pacemakers and 2,238 patients with implantable cardioverter defibrillators (ICDs) at 225 US sites and followed them for a median of 22.9 months.

Short episodes were defined as those that began and ended during the same electrogram. Typically, they lasted less than 20 seconds from onset to offset. Long episodes were defined as all others.

Patients underwent a total of 37,531 electrograms, which detected at least 1 episode of AF or atrial tachycardia (AT) in half of all patients. There were 359 deaths during the study period, which also saw 342 patients hospitalized 478 times for related clinical events such as stroke. Of those patients, 265 were hospitalized for heart attacks and 47 of them were hospitalized for stroke.

Patients who suffered clinical events were more likely than other patients to have experienced at least 1 electrogram-documented long episode of AF or AT or both (31.9% vs. 22.1% for pacemaker patients and 28.7% vs. 20.2% for ICD patients; P<0.05 for both groups).

Patients who suffered clinical events were not, however, any more likely than other patients to have suffered at least 1 electrogram-documented short episode (but no long episode) of AF, AT or both (5.1% vs. 7.9% for pacemaker patients and 11.5% vs. 10.4% for ICD patients; P=0.21 and 0.66, respectively).

“In the RATE Registry, rigorously adjudicated short episodes of AT/AF, as defined, were not associated with increased risk of clinical events compared with patients without documented AT/AF,” the study authors wrote in Circulation.

The biggest implication of the new finding may be that patients who have short episodes of AF or AT — but not long episodes &mdash; may not require any treatment designed to reduce the risk of stroke or other adverse events

“We knew that people with atrial fibrillation are at higher risk of stroke, but the next question was, how much atrial fibrillation?” said the study’s lead author, Steven Swiryn, MD, a clinical professor of cardiology at the Feinberg School of Medicine at Northwestern University in Chicago. “Other studies have shown that prolonged episodes of atrial fibrillation pose a risk, but what about short ones? The answer until this study was ‘no one knows.’ Now we have good solid data that if all you have is short episodes of atrial fibrillation, the risk is so low that it doesn’t warrant anticoagulants.”

Even if subsequent research confirms that patients with short AF episodes can safely forego treatment, they may not be able to forego it for long. The new study showed that patients who begin by exhibiting only short AF episodes were more likely than others to suffer long episodes by the end of the study period (HR 1.27, 95% CI 0.99-1.63). Only 9% of all study patients exhibited only short episodes of AF or AT during the study period.

The study authors recommended close monitoring of short-episode patients to insure timely detection of any increase in episode length.

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