title: Visualization of left atrial appendage and assessment of its function by transthoracic second harmonic imaging and contrast-enhanced pulsed Doppler.
abstract: BACKGROUND
  Low flow velocity within the left atrial appendage, as assessed by transoesophageal echocardiography, is a predictor of thromboembolism and of a low success rate of cardioversion of atrial fibrillation. However, the semi-invasive nature does limit its serial application as a screening technique.
  
  
  RESULTS
  We investigated the value of transthoracic second harmonic echocardiography and pulsed Doppler at baseline and after intravenous contrast injection to visualize the left atrial appendage and assess blood flow velocities within its cavity. We studied 51 consecutive patients undergoing transoesophageal echocardiography. After transoesophageal echocardiography, transthoracic second harmonic imaging was performed and the left atrial appendage was visualized in 46 patients. Interpretable pulsed Doppler tracings of left atrial appendage flow were obtained at baseline in 39 patients and in 45 patients during Levovist administration. The correlations between peak emptying velocity of left atrial appendage as measured by transoesophageal echocardiography and by transthoracic standard and contrast-enhanced Doppler were 0.81 and 0.91, respectively. The agreement between transoesophageal echocardiography and transthoracic contrast-enhanced pulsed Doppler echocardiography in classifying left atrial appendage flow velocity patterns was 93%. Left atrial appendage thrombus was detected by transthoracic second harmonic imaging in only one of the eight patients shown by transoesophageal echocardiography to have a thrombus. However, all but one of the patients with left atrial appendage thrombus and/or spontaneous echocardiographic contrast at transoesophageal echocardiography had <30cm/s left atrial appendage flow velocity by transthoracic Doppler.
  
  
  CONCLUSIONS
  This study shows that left atrial appendage can be visualized by transthoracic second harmonic imaging and that the flow velocity within its cavity is reliably measured by pulsed Doppler in a substantial fraction of patients. Contrast enhancement improves the feasibility and the accuracy of transthoracic evaluation of left atrial appendage flow velocity. The practical value of these results in predicting thromboembolic risk and success of cardioversion of atrial fibrillation needs to be proved by prospective studies.
authors.affiliation: Department of Cardiology, A. Manzoni Hospital, Lecco, Italy. maxpozz@libero.it
authors.forename: M
authors.initials: M
authors.lastname: Pozzoli
authors.forename: A
authors.initials: A
authors.lastname: Selva
authors.forename: D
authors.initials: D
authors.lastname: Skouse
authors.forename: E
authors.initials: E
authors.lastname: Traversi
authors.forename: R
authors.initials: R
authors.lastname: Mancini
authors.forename: G
authors.initials: G
authors.lastname: Bana
authors.forename: A
authors.initials: A
authors.lastname: Rossi
authors.forename: M
authors.initials: M
authors.lastname: Bossi
mesh_terms: D000368:Aged; D020517:Atrial Appendage / Q000000981:diagnostic imaging*; D001783:Blood Flow Velocity; D003287:Contrast Media; D004452:Echocardiography; D018619:Echocardiography, Doppler, Pulsed; D017548:Echocardiography, Transesophageal; D005260:Female; D006331:Heart Diseases / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D011134:Polysaccharides; D013927:Thrombosis / Q000000981:diagnostic imaging
chemical_list: D003287:Contrast Media; D011134:Polysaccharides; C059891:SHU 508