Success of the procedure is often dependent on mapping and ablating the pulmonary vein antrum, the area proximal to the tubular portion of the pulmonary veins that can encompass a large extent of the posterior wall of the left atrium (Figure 1). However, catheter ablation of atrial fibrillation can place the patient at risk for stroke, cardiac perforation, pulmonary vein stenosis and atrial-esophageal fistula formation. Utilization of techniques and technology to minimize or eliminate these potential risks is vital in order to provide an efficacious technique to a large number of patients safely.

AcuNav (Siemens Medical Solutions, Malvern, Pennsylvania) is a 64-element phased array intracardiac echocardiographic technology (ICE) that utilizes a longitudinal side-fire imaging plane and provides very detailed images of various cardiac structures in standard echocardiographic format (Figure 2). The ICE catheter is inserted into a femoral vein and advanced into the right atrium, where 2D and Doppler imaging of the right atrium, intra-atrial septum, left atrium, and pulmonary veins can be performed. The valvular structures of the heart, right and left ventricles, pericardium, and left atrial appendage can also be visualized. ICE allows real-time observation of catheter position, catheter stability, and lesion formation during radiofrequency ablation. Direct visualization assists in the application of appropriate lesion sets, and can also help prevent complications. This article will outline the utility of ICE in catheter ablation of atrial fibrillation.

Transseptal Puncture

Most techniques for percutaneous catheter ablation require at least one, and some up to three, transseptal punctures. Thrombus formation on sheaths or catheters can occur quickly after transseptal puncture; therefore, aggressive anticoagulation before or immediately after transseptal puncture is critical. Improper transseptal puncture can result in cardiac perforation and tamponade or fistula formation between the right atrium and the ascending aorta. ICE provides direct visualization of the intra-atrial septum, fossa ovalis, and left atrium during transseptal puncture. Tenting of the intra-atrial septum prior to puncture and visualization of contrast/saline injected into the left atrium upon puncture can confirm proper access of the left atrium (Figure 3). In addition, transseptal puncture in the plane of the left pulmonary veins can assure a posterior placement of sheath(s) and catheter(s), allowing for a more direct approach to the pulmonary veins and posterior wall of the left atrium.

Pre-Ablation Anatomical Orientation

There can be significant variability of pulmonary vein and left atrial anatomy.⁵ Three-dimensional (3D) CT/MRI reconstructions of the pulmonary veins often demonstrate common ostia/pulmonary vein antra or supranumery pulmonary veins. Whereas fluoroscopy and 3D mapping systems cannot consistently reveal these abnormalities, ICE can directly follow catheters as they navigate anatomical variability (Figure 4). Pulmonary vein size and Doppler flow through the pulmonary veins can be measured with ICE. In addition, ICE can visualize the esophagus and estimate its proximity to the pulmonary veins (Figure 5).

Confirmation of Catheter Positioning