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Stunning of Left Atrial Appendage after Spontaneous Conversion of Atrial Fibrillation

The transient mechanical dysfunction of atrium and atrial appendage, stunning, has been well documented to occur after pharmacological or electrical cardioversion of atrial fibrillation and flutter.1,2 This phenomenon has been thought to occur also after spontaneous rhythm conversion, although only few such cases have been previously published. We report on a 67-year-old woman with no prior cardiac problems who presented with a 2-day history of dyspnea and chest pain during exercise. The patient had not sensed irregularities in her rhythm. Initial workup revealed atrial fibrillation on ECG and a slightly elevated troponin T. Coronary angiography showed no signs of coronary artery disease. The patient was started on subcutaneous low-molecular weight heparin and warfarin and subsequently transesophageal echocardiography (TEE) was performed to rule out atrial thrombus to allow cardioversion. TEE demonstrated normal ventricular function (ejection fraction 60%) and left atrial size (37 mm) and no thrombus in left atrium or left atrial appendage (LAA). Pulsed Doppler examination of LAA revealed a flow pattern consistent with atrial fibrillation with a peak flow velocity of 0.50 m/sec (Fig. 1A). During the TEE examination the atrial fibrillation spontaneously converted to sinus rhythm after which atrial appendage flow velocities immediately decreased to approximately 0.10 m/sec, indicating atrial stunning (Fig. 1B).