New research has determined that a delay of 12 hours or longer to correct an abnormal cardiac rhythm from atrial fibrillation (AFib) is associated with a greater risk of thromboembolic complications such as stroke.

The research letter, published Aug. 12 in the Journal of the American Medical Association, and led by Ilpo Nuotio, MD, PhD, Division of Medicine, Turku University Hospital, Turku, Finland, was prompted by the 1995 practice guidelines that recommend a limit of 48 hours after the onset of AFib for cardioversion without anticoagulation.

Performing a retrospective study, Nuotio et al. sought to find whether the risk of thromboembolic complications increased when cardioversion without anticoagulation was performed in less than 48 hours. With their primary outcome, a thromboembolic event, defined as a clinical stroke or systemic embolism within 30 days after cardioversion, procedures were divided into groups according to the time to cardioversion: less than 12 hours; 12 hours to less than 24 hours; and 24 hours to less than 48 hours.

Results of the study found that of 2,481 patients with acute AFib, 5,116 successful cardioversions were performed without anticoagulation. Thirty-eight thromboembolic events occurred in 38 patients, 31 of which were strokes. Comparing duration times, incidences of thromboembolic complications increased from 0.3 percent from the less than 12 hours group, to 1.1 percent in the 24 hours to less than 48 hours group.

The authors conclude that "a delay to cardioversion of 12 hours or longer from symptom onset was associated with a greater risk of thromboembolic complications. When the duration of AFib was less than 12 hours, the risk of thromboembolism was low without anticoagulation."

Keywords: Thromboembolism, Blood Coagulation, Stroke, Hospitals, University, Electric Countershock, Embolism