Risks of Embolism with Acute Atrial Fibrillation


Synopsis: Atrial fibrillation lasting less than 48 hours has a low risk of systemic emboli.

Source: Weigner MJ, et al. Ann Intern Med 1997;126: 615-620.

Atrial fibrillation is the most common sustained arrhythmia. Anticoagulation use in atrial fibrillation has been a major focus of recent research. For newly diagnosed atrial fibrillation, the standard of care is to attempt to cardiovert back to sinus rhythm and to intravenously anticoagulate patients for several weeks prior to attempted cardioversion. However, for patients whose duration of atrial fibrillation is known and short, specifically less than 48 hours, the risk of thromboembolism has been presumed to be very low and early cardioversion recommended.

Prior to the study by Weigner and colleagues, no prospective data supporting this low risk were available. All patients admitted to two university hospitals over five years in the early 1990s were screened. About 20% (n = 375) were clinically estimated based on acute onset of palpitations, dyspnea, angina, or dizziness lasting less than 48 hours. Patients on long-term warfarin were excluded. Ninety-five percent of patients converted back to sinus rhythm at an average of 1.7 hospital days. Two-thirds of the patients converted spontaneously without antiarrhythmics or cardioversion). Only three (0.8%) patients, all of whom spontaneously converted, had embolic events.


This study convincingly shows that if atrial fibrillation is of short-duration, the embolic risks associated with early cardioversion are low. I was surprised that two-thirds of patients spontaneously cardioverted. Maybe the best strategy is to limit initial treatments to fixing the electrolyte disorder and/or volume overload prior to starting the anti-arrhythmics.