Sunday, November 13, 2016

Short Episodes of Atrial Fibrillation Don’t Increase Stroke Risk

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 10 seconds?”
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 don’t.”
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.