A delay of 12 hours or longer to correct an abnormal cardiac rhythm from atrial fibrillation was associated with a greater risk of thromboembolic complications such as stroke, according to a study in JAMA.
In 1995, practice guidelines recommended a limit of 48 hours after the onset of atrial fibrillation (AF) for cardioversion (the conversion of a cardiac rhythm from abnormal to normal) without anticoagulation. Whether the risk of thromboembolic complications is increased when cardioversion without anticoagulation is performed in less than 48 hours is unknown, according to background information in the article.
Ilpo Nuotio, M.D., Ph.D., of Turku University Hospital, Turku, Finland and colleagues conducted a study that included patients with a successful cardioversion in the emergency department within the first 48 hours of AF. The primary outcome, a thromboembolic event, was defined as a clinical stroke or systemic embolism (blood clot) within 30 days after cardioversion. Procedures were divided into groups according to the time to cardioversion: less than 12 hours (group 1), 12 hours to less than 24 hours (group 2), and 24 hours to less than 48 hours (group 3).
Of 2,481 patients with acute AF, 5,116 successful cardioversions were performed without anticoagulation. Thirty eight thromboembolic events occurred in 38 patients (0.7 percent); 31 were strokes. The incidence of thromboembolic complications increased from 0.3 percent in group 1 to 1.1 percent in group 3. In analysis, time to cardioversion longer than 12 hours was an independent predictor for thromboembolic complications.