Is early cardioversion of atrial fibrillation, facilitated by transesophageal echocardiography, safe and effective?

BACKGROUND: Atrial fibrillation (AF) is the most common sustained arrhythmia and is an important contributor to cardiovascular morbidity and mortality. To prevent thromboembolism, physicians conventionally employ anticoagulant therapy for 3 to 4 weeks before an attempted cardioversion. Studies suggest that the duration of AF before cardioversion is a critical determinant of the reestablishment and maintenance of sinus rhythm. This study attempts to determine whether early transesophageal echocardiography (TEE), by ruling out a thrombus, can safely lead to more rapid cardioversion with improved outcomes.

POPULATION STUDIED: The subjects were 539 patients with AF recruited at 2 university hospitals over a 9-year period.

STUDY DESIGN AND VALIDITY: This was a prospective cohort study. Patients were excluded if estimated duration of AF was less than 2 days, if duration of AF was unknown, or if patients received long-term warfarin anticoagulation before admission. At admission, patients were given intravenous heparin and oral warfarin. Once therapeutic partial thromboplastin time was obtained, TEE was performed or supervised by 1 of 15 attending physicians, and all images were reviewed by at least 2 experienced practitioners to reach consensus for diagnosis of atrial thrombus. If no thrombus was detected, patients underwent chemical or direct-current cardioversion. However, if thrombus was demonstrated, cardioversion was deferred until follow-up TEE showed no thrombus after conventional warfarin treatment. For 1 month following cardioversion, patients continued to receive warfarin and were followed up for evidence of clinical thromboembolic events. Patients were followed up for 1 year to determine their health status. There are some methodologic concerns to this study. First, without randomization to a control group (anticoagulation 4 weeks preceding cardioversion), it is difficult to assess whether there is any direct effect of the early TEE strategy on the favorable outcomes reported. Second, the mode of cardioversion and use or choice of post-cardioversion antiarrhythmic medication were left to the discretion of the patient’s attending physician; this provides the opportunity for bias between patient groups. Third, objective surveillance data from 24-hour Holter monitoring was not used; thus, true incidence of AF recurrence was likely underestimated. Finally, though there were no complications attributed to the early cardioversion approach, safety was inferred by comparison with previously published studies rather than directly measured. This method could have underestimated asymptomatic thromboembolic events.

OUTCOMES MEASURED: The study compared the incidence of recurrent AF and prevalence of sinus rhythm at 1 year in those patients with clinically estimated initial AF of less than 3 weeks’ duration with those with initial AF greater than 3 weeks’ duration.

RESULTS: No significant differences were noted between the 2 studied groups on the basis of age, sex, left ventricular dysfunction, left atrial dimension, left/right atrial spontaneous echocardiographic contrast, or severity of mitral regurgitation. Patients who underwent cardioversion less than 3 weeks after the onset of AF had a lower likelihood of recurrence over the following year than did patients with more than 3 weeks of AF (41.1% vs 57.9%; P <.01). For every 6 patients who underwent cardioversion immediately rather than after 3 to 4 weeks of anticoagulation, there would be 1 less patient with recurrence of AF during the following year (number needed to treat [NNT]=6). At 1 year, the prevalence of sinus rhythm was also higher in the patients who received earlier cardioversion (65.8% vs 51.3%, P <.03; NNT=7). There were no complications attributed to early cardioversion.