Shadows on the Cave Wall: The Role of Transesophageal Echocardiography in Atrial Fibrillation

Atrial fibrillation, the most common arrhythmia requiring therapy, affects 0.4% of the general population and 2% to 5% of persons older than the age of 60 years [1-3]. Moreover, atrial fibrillation has become the focus of renewed interest and investigation. Current management strategies include cardioversion and antiarrhythmic drugs to maintain sinus rhythm and the alternative approach of rate control. In the latter, the ventricular response is modified by the use of dromotropic drugs, catheter ablation, or radiofrequency modification of the atrioventricular node. In both strategies, anticoagulation or platelet inhibitor therapy is used for preventing embolic stroke.

The use of anticoagulation to manage patients having cardioversion is controversial and is germane to the role of transesophageal echocardiography in evaluating patients with atrial fibrillation and to the study by Manning and associates [4] in this issue. It is well established that a thromboembolic event may follow cardioversion within hours or days of the restoration of sinus rhythm [5, 6]. Nonrandomized studies suggest that the risk for embolism is reduced by the administration of anticoagulant agents for at least 3 weeks before cardioversion but that this therapy is necessary only in patients with atrial fibrillation lasting 72 hours or more [5, 6]. Manning and colleagues [7] previously found that among patients in whom no thrombus was seen on transesophageal echocardiography at hospital admission, cardioversion can be done safely without previous anticoagulation. A subsequent study [8] confirmed the anecdotal experience of many physicians: Emboli can occur in patients who have not received anticoagulants even though no thrombus had developed before cardioversion. A landmark Australian study by Fatkin and colleagues [9] provided a logical explanation for this finding: A delay may exist between the restoration of electrical sinus rhythm and the return of mechanical contraction, that is, atrial stunning. During this period, …