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.

Transesophageal echocardiography (TEE) is the clinical standard for diagnosis of left atrial appendage (LAA) and right atrial appendage (RAA) thrombi before cardioversion or instrumentation of the left atrium during ablation proce- dures.1-5 Occasionally, TEE cannot be performed because of anatomic limitations requiring an alternative imaging strategy to exclude LAA thrombi. Phased-array intracardiac echocardiography (ICE) is routinely used during atrial fibrillation (AF) ablation procedures to guide transseptal puncture and detect complications. The standard position of the transducer is in the right atrium (RA). This allows adequate visualization of the interatrial septum and body of the left atrium (LA) but not of the LAA because of significant physical distance from the transducer. Imaging of the LAA from closer anatomic structures such as the right ventricular outflow tract (RVOT) and pulmonary artery (PA) can improve visualization of the LAA. If ICE provided imaging of the LAA comparable to TEE with a good safety profile, it could potentially serve as an alternative to TEE in patients undergoing catheter ablation. Such an approach could reduce risk, cost, and patient discomfort associated with TEE combined with ICE. In this prospective blinded study, we sought to directly compare the sensitivity and specificity of TEE with ICE for detection of LAA and RAA anatomy and thrombus in patients with atrial tachyarrhythmias undergoing catheter ablation.

Inclusion Criteria:

• Patients able to understand and critically review the informed consent.
• Patients presenting for an AF and/or AFL ablation procedure who have clinical indication for TEE and ICE.

Exclusion Criteria:

• Patients in whom placement of an ICE catheter for adequate atrial visualization is technically not feasible.
• Patients requiring urgent cardioversion.
• Patients with a contraindication for TEE
• Inability to give informed consent.

Patients with drug-refractory, symptomatic, paroxysmal or persistent atrial fibrillation or atrial flutter requiring a clinical indicated ablation procedure.

Patients enrolled into study that underwent ICE and TEE imaging.

During enrollment, the clinical ablation procedure, while in the hospital.

All patients were screened for any complications at the conclusion of the clinical procedure (average of 6 hour period).

This study compared TEE and ICE for visualization of the LAA and RAA in a specific patient population with nonvalvular AF treated with chronic anti-coagulation. The utility of ICE in other patient populations has not been examined.