Northwestern: Patients with pacemakers or defibrillators who experience only short episodes of atrial fibrillation are not at an increased risk for stroke over a two-year follow-up, according to a Northwestern Medicine study published in Circulation. The findings suggest that treating this population with anticoagulants may not be necessary. Atrial fibrillation (AF) is a common heart rhythm disorder and is associated with an increase in the risk of embolic stroke. As such, anticoagulants are often prescribed to patients with AF. But while the therapy is often effective, it also carries a risk of bleeding.
“We all accept that given a high enough risk of stroke in a patient,
and a low enough risk of bleeding, patients with atrial fibrillation
should be anticoagulated,” Swiryn said. “But none of the guidelines have
ever said how much atrial fibrillation is necessary to invoke that
strategy. Is it a whole day’s worth of atrial fibrillation or an hour or
The investigators sought to determine what amount of AF was actually
associated with an increased risk of stroke, and whether patients who
experienced only short bursts of AF were at a high enough risk to
warrant anticoagulant therapy.
Pacemakers and defibrillators don’t automatically diagnose short
episodes of AF accurately, Swiryn said, so to conduct the study, he and a
team of investigators personally analyzed 37,531 electrograms (EGMs)
recorded by the device, from more than 5,000 patients over a two-year
follow-up. The subjects were all enrolled in the RATE Registry, a study
that tracked patients with pacemakers or defibrillators.
The results of their analysis confirmed that extended periods of AF
were associated with an uptick in the risk of clinical events, including
hospitalization for AF, stroke, heart failure and death.
But short episodes — which hadn’t been addressed by previous studies —
were not associated with adverse outcomes, including stroke. Short
episodes were defined as when the onset and offset of AF occurred within
the same EGM recording (typically less than 20 seconds).
“Therefore, as long as there are only brief episodes, anticoagulation
probably is not necessary,” Swiryn said. “So now we can go back to the
guidelines and further refine who we have to anticoagulate and who we
The paper was also co-authored by Donald Lloyd-Jones, MD, chair of Preventive Medicine.
The RATE Registry was funded by St. Jude Medical, which manufactures
pacemakers and defibrillators. Swiryn and Lloyd-Jones are paid
consultants for St. Jude Medical.