title: External validation of a novel transthoracic echocardiographic tool in predicting left atrial appendage thrombus formation in patients with nonvalvular atrial fibrillation.
abstract: BACKGROUND
  A recent study demonstrated that in patients with nonvalvular atrial fibrillation (AF), a ratio of left ventricular ejection fraction (LVEF) to the left atrial volume index (LAVI) of <1.5 has 100% sensitivity for detecting left atrial appendage (LAA) thrombus. We sought to validate this prediction tool in an external cohort.
  
  
  METHODS
  We conducted a cohort study of consecutive AF patients who underwent transoesophageal echocardiogram (TEE) to 'rule-out' LAA thrombus and had a prior transthoracic echocardiogram (TTE). The LAVI and LVEF were measured to calculate LVEF/LAVI ratio. The sensitivity and specificity of LVEF/LAVI <1.5 were calculated.
  
  
  RESULTS
  Among 215 subjects, 19 (8.8%) had LAA thrombus and also had a higher mean CHADS2 score (2.5 vs. 1.9, P = 0.04), lower mean LVEF (24 vs. 44%, P < 0.001), higher mean LAVI (44 mL/m2 vs. 30 mL/m2, P < 0.001), and higher prevalence of cardiac failure (79 vs. 52%, P = 0.02). The LVEF and LAVI were found to be independent predictors of LAA thrombus (P < 0.05). The LVEF/LAVI ratio diagnosed LAA thrombus with an area under the curve = 0.83 by the receiver operator characteristics curve analysis (P < 0.001). All 19 (100%) subjects with LAA thrombus had LVEF/LAVI <1.5 vs. 87 (44%) among those without LAA thrombus (P < 0.001). The sensitivity and specificity of LVEF/LAVI <1.5 were 100 and 55.6%, respectively.
  
  
  CONCLUSIONS
  This investigation validates a simple TTE prediction rule to exclude the diagnosis of LAA thrombus, which may obviate the need for pre-cardioversion TEE in selected patients with nonvalvular AF.
authors.affiliation: Section of Cardiology, Rush University Medical Center, 1653 W. Congress Pkwy, Chicago, IL 60612, USA.
authors.forename: Rami
authors.initials: R
authors.lastname: Doukky
authors.forename: Abha
authors.initials: A
authors.lastname: Khandelwal
authors.forename: Enrique
authors.initials: E
authors.lastname: Garcia-Sayan
authors.forename: Heather
authors.initials: H
authors.lastname: Gage
mesh_terms: D000368:Aged; D020517:Atrial Appendage / Q000000981:diagnostic imaging*; D001281:Atrial Fibrillation / Q000150:complications* / Q000000981:diagnostic imaging*; D004452:Echocardiography / Q000295:instrumentation*; D017548:Echocardiography, Transesophageal; D005260:Female; D006801:Humans; D008297:Male; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D013927:Thrombosis / Q000000981:diagnostic imaging* / Q000209:etiology*
keywords: Atrial fibrillation; Ejection fraction; Left atrial appendage thrombus; Left atrial volume; Transoesophageal echocardiogram (TEE); Transthoracic echocardiogram (TTE)