By Edward P. Gerstenfeld, MD

SOURCE: Anter E, et al. Comparison of intracardiac echocardiography and transesophageal echocardiography for imaging of the right and left atrial appendages. Heart Rhythm 2014;11:1890-1897.

This article originally appeared in the January 2015 issue of Clinical Cardiology Alert.

Transesophageal echocardiography (TEE) is commonly performed prior to atrial fibrillation (AF) ablation to exclude left atrial appendage thrombus. The purpose of this study was to compare TEE and intracardiac echocardiography (ICE) for assessing left atrial appendage (LAA) anatomy and thrombus. This study was a prospective, blinded study that enrolled 71 patients referred for ablation of AF. TEE and ICE were performed simultaneously to assess for thrombi, spontaneous echo contrast, and LAA dimensions. Imaging of the LAA was achieved in all 71 patients using ICE but in only in 69 patients using TEE because of inability to intubate the esophagus. A total of four thrombi were diagnosed (three LAA, one renin-angiotensin-aldosterone). All were detected by ICE but only one by TEE. Diagnostic imaging of the LAA was achieved in 71 patients (100%) with ICE and in 62 patients (87.3%) with TEE (P < .002). Spontaneous echo contrast was more commonly diagnosed with ICE (P < .01). There was strong correlation between TEE and ICE for LAA length (r = 0.71), width (r = 0.94), and area (r = 0.88). Image quality with ICE was highest from the pulmonary artery and lowest from the right atrium. The authors concluded that ICE imaging is a viable alternative to TEE for visualization of the LAA during catheter ablation procedures.

COMMENTARY

The AF ablation guidelines recommend TEE prior to AF ablation in patients who have not been therapeutically anticoagulated for 3 weeks prior to the procedure. However, a TEE is commonly performed in many centers, even when patients have been anticoagulated prior to the procedure. This is because ablation of persistent AF seems to carry a higher stroke risk and because catheters will often be manipulated inside the left atrial appendage. Performing a TEE adds time, cost, and possible additional complications to the ablation procedure. The costs are felt to be justified by the reduction in stroke risk; however, many studies have found the incidence of thrombi detected prior to AF ablation to be exceedingly low. ICE is an alternative imaging modality that is typically used during AF ablation procedures in some centers to guide transseptal puncture and catheter positioning. ICE can view the LAA from several locations: the right atrium, the right ventricular outflow tract, and the pulmonary artery, which lies adjacent to the LAA. In this study, the authors prospectively compared ICE and TEE for LAA imaging and the presence of thrombus. Interestingly, diagnostic imaging of the LAA was achieved in all patients using ICE but only 87% using TEE. ICE was also superior to TEE for detecting LAA thrombi (as stated above, TEE missed three of four thrombi).

The findings, though in a small group of patients, are provocative. One might question the expertise of the authors using TEE, given successful esophageal intubation in only 87% and absence of visualized thrombus in three of four cases. The GE Vivid E9 echocardiography machine was used for TEEs, and I know echocardiographers at our institution do feel that the image quality does vary by manufacturer. However, the authors have significant experience performing TEEs, including the senior author who first brought the use of TEEs for excluding LAA thrombus to the mainstream. Nevertheless, it is possible that since an alternative imaging modality was available, the authors were less aggressive in trying to intubate the esophagus in difficult patients. It should also be noted that the authors were experienced in the use of ICE, and that diagnostic views were typically obtained from the pulmonary artery (PA). Although no complications were reported in this manuscript, advancing the ICE probe through the right ventricular (RV) to the PA does add some risk, and can be challenging in patients with RV enlargement or pulmonary hypertension.

Nevertheless, the paper does support the use of ICE for LAA screening in low-risk patients undergoing AF ablation. This could save significant time and cost prior to AF ablation at centers where ICE is used routinely for AF ablation. Additional experience with larger numbers of patients will be needed, however, before ICE can be recommended as an alternative screening modality to TEE for patients undergoing AF ablation.