Nonrheumatic atrial fibrillation is common in elderly and associated with an increased risk for thromboembolism. Left atrial spontaneous echo contrast(SEC) and thrombus. which are easily detected by transesophageal echocardiography(TEE) in patients with rheumatic mitral valve disease and atrial fibrillation, have been known as markers of thromboembolism. However, most of the previous studies on left atrial SEC and thrombus were performed in rheumatic mitral valve disease or various conditions including rheumatic mitral valve disease. Therefore this study was underaken in order to investigatd 1) the prevalence of left atrial SEC and thrombus, and 2) clinical and echocardiographic variables related to left atrial SEC and thrombus in nonrheumatic atrial fibrillation.

In patients with estabished atrial fibrillation over 7 days, we examined the clinical gistory and performed transthoracic echocardiography(TTE) and TEE simultaneously. Enlisted patients were those without rheumatic mitral valve disease, prosthetic valves, previous thromboembolism, and recent anticoagulant therapy.

1) Left atrial SEC was detected in 32(62.7%) of 51 patients and left atrial thrombus in 10(19.6%). All thrombi were located in the left atrial appendage.

2) In univariate analysis, SEC positive group showed higher prevalence of congestive heart failure(CHF)(56.3% vs 0%, p<0.001), lower ejection fraction(42.2±14.1% vs 50.8±9.7%, p<0.05), lower left atrial appendage blood flow velocity(peak positive flow velocity ;18.7±11.1cm/sec vs 32±12.4cm/sec, p<0.01, and peak negative flow velocity ; 21.4±12.4cm/sec vs 31.9±12.8cm/sec, p<0.01) than SEC negative group. Multivariate analysis identifed CHF as an independent variable related to left atrial SEC(p=0.02, Odds ratio ; 2.38, 95% CI ; 1.18-4.82).

3) In univariate analysis. left atrial thrombus positive group showed higher prevalence of CHF(70% vs 26.8%, p<0.05), larger left atrial demension(34±3.4mm/m² vs 30.6±4.6mm/m², p<0.05) than thrombus negative group. Multivariate analysis identifed CHF as an independent variable related to left atrial thrombus(p=0.04, Odds ratio ; 4.30, 95% CI ; 1.11-16.68).

4) Left atrial thrombus is more frequent in SEC positive group than in SEC negative group(28.1% vs 5.3%), however, there was no statistical significance(p=0.07).

1) Left atrial SEC is common in nonrheumatic atrial fibrillation and significantly related to CHF.

2) Left atrial thrombus is frequently detected in SEC positive patients, however, it is more realted to CHF than left atrial SEC itself.