Comparison of Intracardiac Echocardiography and Transesophageal Echocardiography

The presence of intracardiac thrombi and their propensity for systemic embolism is a major concern in patients with atrial fibrillation (AF) and atrial flutter (AFL) undergoing cardioversion and ablation procedures. Transesophageal echocardiography (TEE) is the clinical gold standard imaging modality for visualization of the right atrial appendage (RAA) and left atrial appendage (LAA) for detection of thrombi as well as risk factors associated with thrombus formation, including spontaneous echo contrast and low LAA velocity. However, TEE is a moderately invasive procedure that incurs additional risk, cost, and patient discomfort. In addition, thrombus detection via TEE may be ambiguous, and another tool capable of confirming uncertain TEE findings is desirable. This is particularly crucial in cases when adequate LAA imaging cannot be acquired or if TEE is clinically contraindicated, requiring alternative imaging modalities that can visualize these structures.

Phased-array intracardiac echocardiography (ICE) provides high-imaging resolution and is routinely used during atrial fibrillation (AF) ablation procedures for transseptal puncture and periprocedural catheter visualization. A majority of imaging acquired during AF ablation is performed with the ICE catheter in the right atrium (RA). However, these standard views are often unable to provide sufficient visualization of the LAA structure due to the relatively long distance between the ICE catheter and LAA.

Placement of the ICE catheter in the pulmonary artery (PA) provides improved visualization of the LAA over other locations by reducing the anatomic distance between the imaging catheter and structure of interest. Recent retrospective studies have confirmed improved assessment of the LAA with ICE imaging from the PA and equivocal sensitivity and specificity when compared with TEE for evaluation of LAA thrombus. However, these studies did not systematically evaluate the presence of SEC, flow velocity, the LAA dimensions, or the RAA.

Although these studies support the use of ICE imaging from the PA to clarify or confirm TEE findings, a prospective and blinded study evaluating both the LAA and RAA in its entirety is required. We hypothesize that this prospective and blinded study will confirm ICE as non-inferior to TEE in the assessment of LAA and RAA structure and for the detection of thrombi.