LEFT ATRIAL APPENDAGE FUNCTION AND THROMBUS FORMATION IN ATRIAL FIBRILLATION-FLUTTER - A TRANSESOPHAGEAL ECHOCARDIOGRAPHIC STUDY

Objectives. The purpose of this study was to investigate left atrial a ppendage size, function and thrombus prevalence in patients with atria l ''fibrillation-flutter.'' Background. Thrombus formation and periphe ral embolization in atrial fibrillation are related to left atrial app endage dysfunction. Embolization occurs less frequently in atrial flut ter. It is not known whether the atrial appendage in fibrillation flut ter, which has an intermediate appearance on the surface electrocardio gram (ECG), has distinct characteristics that could affect thrombus fo rmation. Methods. Sixty-one patients with atrial tachyarrhythmias unde rwent transesophageal echocardiographic examination of the left atrial appendage, Appendage area, peak emptying velocity and the presence of thrombus and spontaneous echo contrast were determined. The results f or 14 patients with fibrillation-flutter (based on ECG fibrillatory wa ve characteristics) were compared with those for 30 patients with atri al fibrillation and 17 patients with atrial flutter. Results. Both fib rillation-flutter and atrial fibrillation were associated with chaotic appendage flow patterns with similarly low peak emptying velocities ( 18 +/- 8 and 17 +/- 10 cm/s, mean +/- 1 SD, respectively). Atrial flut ter was associated with a regular pattern of appendage contraction and a significantly higher peak emptying velocity (42 +/- 18 cm/s, p < 0. 0001). Mean appendage area was similar for fibrillation flutter and fi brillation (6.3 +/- 2.2 and 6.7 +/- 2.1 cm(2), respectively) but was s ignificantly smaller for atrial flutter (5.3 +/- 1.4 cm(2), p < 0.05). The prevalence of left atrial appendage thrombus was similar for fibr illation-flutter and atrial fibrillation (40% and 29%, respectively), whereas no patient with atrial flutter had a thrombus (p < 0.05). Simi larly, the presence of spontaneous echo contrast was higher for fibril lation-flutter (50%) and atrial fibrillation (40%) than for atrial flu tter (6%, p < 0.05). Conclusions. Left atrial appendage size and funct ion in atrial fibrillation flutter are indistinguishable from those of typical atrial fibrillation, and the frequency of thrombus and sponta neous echo contrast is similarly high. This is in contrast to atrial f lutter, which is characterized by a smaller, more contractile left atr ial appendage and a lower frequency of thrombus and spontaneous echo c ontrast.