A Prospective Comparison of Harmonic Transthoracic and Transesophageal Echocardiography for Identifying Left Atrial Thrombi in Patients with Atrial Flutter and/or Fibrillation Prior to Cardioversion

摘要

Objective: To compare the value of current harmonic transthoracic and transesophageal echocardiography for assessing echocardiographic markers of thromboembolic risk and identify left atrial thrombi in patients with atrial fibrillation and atrial flutter prior to cardioversion and/or overdrive stimulation. Transesophageal echocardiography has been suggested for guiding cardioversion in patients with atrial fibrillation and atrial flutter, because of its high accuracy for identifying left atrial thrombi. More recent studies have demonstrated that harmonic echocardiography may allow transthoracic detection of left atrial thrombi and assessment of left atrial appendage function. Setting: Tertiary cardiac referral centre. 172 Patients with atrial fibrillation and/or atrial flutter who were scheduled for cardioversion and/or overdrive stimulation were examined both by harmonic transthoracic and multiplane transesophageal echocardiography by independent observers to assess left atrial chamber and appendage size and peak emptying velocities. In addition, the presence of thrombi was determined. All patients were followed for 4 weeks after the procedure to assess for thromboembolic complications. Harmonic transthoracic echocardiography allowed imaging of the left atrial appendage and recording of its velocities in 83 % and 74 % of cases, respectively. Transthoracic and transesophageal echocardiographic measurements of peak left atrial appendage velocities did not differ significantly (0.4 (0.14) versus 0.35 (0.17) m/s; P = 0.14). Overall 11 thrombi were detected by transthoracic echocardiography. Transesophageal echocardiography confirmed the presence of all thrombi. One additional thrombus was diagnosed in a patient with a negative transthoracic echocardiographic study. Thus, the sensitivity and specifity of harmonic transthoracic echocardiography for identifying a thrombus were 92 % and 91 %, respectively. Logistic regression analysis revealed that a peak left atrial appendage velocity greater than 0.25 m/s was the only independent transthoracic parameter for the exclusion of left atrial thrombi with an odds ration of 4.4 (95 % CI 1.4 to 14.5). None of the study patients had a thromboembolic complication after cardioversion or overdrive stimulation. Modern echocardiographic systems with harmonic transthoracic echocardiography allow the identification of large left atrial appendage thrombi with a high degree of confidence. Because the specificity of identifying left atrial appendage thrombi is very high for harmonic transthoracic echocardiography, transesophageal echocardiographic examinations may be omitted in patients with the transthoracic diagnosis of thrombi. If transthoracic recording of left atrial appendage velocities is feasible, it may be possible to identify a thrombogenic milieu by transthoracic echocardiography prior to cardioversion.