PREVALENCE AND CLINICAL-SIGNIFICANCE OF LEFT ATRIAL THROMBUS IN NONRHEUMATIC ATRIAL-FIBRILLATION

The prevalence and clinical significance of left atrial thrombus were prospectively investigated in a consecutive series of 219 patients wit h chronic nonrheumatic atrial fibrillation using transesophageal echoc ardiography. Fifteen left atrial thrombi were detected in 15 of the 21 9 patients (6.8%); 12 of these thrombi (80%) were confined to the left atrial appendage. Left atrial spontaneous echo contrast was visualize d in 85 patients (39%). All the thrombi were found in the left atria w ith spontaneous echo contrast. Patients with left atrial thrombus had significantly lower left ventricular ejection fraction than those with out (49+/-14% vs. 59+/-14%; P<0.05). Multivariate analysis among clini cal and transthoracic echocardiographic variables showed that left ven tricular ejection fraction <50% was the only independent predictor for the presence of left atrial thrombus. A history of thromboembolism wa s significantly more frequent in patients with left atrial thrombus th an in those without (73% vs. 32%; P<0.005). The presence of left atria l thrombus was more specific than spontaneous echo contrast for predic ting history of thromboembolism (97% vs. 80%), but its sensitivity was significantly lower (14% vs. 73%). We conclude that: (1) Transesophag eal echo-detected left atrial thrombus is not uncommon in patients wit h chronic nonrheumatic atrial fibrillation and is exclusively observed in those with left atrial spontaneous echo contrast. (2) Impaired lef t ventricular systolic function may predispose the left atrial thrombu s formation. (3) Left atrial thrombus is a highly specific but insensi tive predictor for thromboembolic events. Copyright (C) 1997 Elsevier Science Ireland Ltd.