RISK FOR CLINICAL THROMBOEMBOLISM ASSOCIATED WITH CONVERSION TO SINUSRHYTHM IN PATIENTS WITH ATRIAL-FIBRILLATION LASTING LESS-THAN 48 HOURS

Background: It has been assumed that cardioversion in patients with at rial fibrillation lasting less than 48 hours is associated with a low risk for thromboembolism. However, no clinical data support this assum ption. Objective: To determine the incidence of cardioversion-related clinical thromboembolism among patients presenting with atrial fibrill ation lasting less than 48 hours. Design: Patients were prospectively identified on admission, and clinical data on the duration of atrial f ibrillation were recorded. Data on cardioversion and thromboembolism w ere obtained retrospectively from hospital and outpatient records. Set ting: Academic medical center. Patients: 1822 consecutive patients adm itted to the hospital for atrial fibrillation were screened. Three hun dred seventy-five adults (mean age +/- SD, 68 +/- 16 years) with atria l fibrillation that had lasted less than 48 hours were identified. One hundred eighty-one patients (48.3%) had a history of atrial fibrillat ion; 23 (6.1%) had a history of thromboembolism. Results: 357 patients (95.2%) converted to sinus rhythm during the index admission; spontan eous conversion occurred in 250 patients (66.7%) and active pharmacolo gic or electrical conversion was done in 107 patients (28.5%). Three p atients (0.8% [95% CI, 0.2% to 2.4%]), all of whom had converted spont aneously after ventricular rate control was begun, had a clinical thro mboembolic event: One had a stroke, 1 had a transient ischemic attack, and 1 had a peripheral embolus. None of these 3 patients had a histor y of atrial fibrillation or thromboembolism, and all had normal left v entricular systolic function. Conclusion: Among patients presenting wi th atrial fibrillation that was clinically estimated to have lasted le ss than 48 hours, the likelihood of cardioversion-related clinical thr omboembolism is low. These data support the current recommendation for early cardioversion in these patients.