INTRODUCTION

Intracardiac echocardiography (ICE) is increasingly being used to guide a variety of percutaneous interventional procedures, including catheter ablation of atrial or ventricular arrhythmias, closure of atrial septal defects, left atrial appendage (LAA) occlusion, balloon mitral valvulo-plasty, and transcatheter aortic valve replacement.

In electrophysiology procedures, ICE can provide detailed real-time imaging of cardiac anatomy and continuous monitoring of the catheters position, potentially enhancing procedural success and safety. It reduces fluoroscopy exposure to both the patient and the operator, and facilitates early recognition of complications such as pericardial effusion.

In this chapter, we review the applications of ICE in the context of epicardial electrophysiology interventions.

AVAILABLE ICE SYSTEMS

Two different ICE systems are available for commercial use, radial or rotational ICE and phased-array ICE.¹

Radial or Rotational ICE

The radial/rotational ICE system uses a single piezoelectric crystal mounted at the tip of a nonsteerable catheter. It provides cross-sectional images in a 360-degree radial plane perpendicular to the long-axis of the catheter and only is useful for near-field imaging (up to 5 cm). Examples are the UltraICE catheter (Boston Scientific, Natick, MA) and FORESIGHT ICE system (Conavi Medical, Toronto, Ontario, Canada).

Phased-array ICE

Phased-array ICE consists of a 64-element transducer mounted on the distal end of a steerable catheter. This catheter produces a wedge-shaped image that is displayed on a conventional ultrasound workstation. Phased-array ICE has several advantages over the mechanical rotational systems, including greater depth of penetration (up to 15 cm), greater maneuverability, and the ability to acquire Doppler and color flow imaging. The two available catheters are the AcuNav (Siemens-Acuson, Mountain View, CA) and ViewFlex Xtra (Abbott Vascular, St. Paul, MN). Phased-array ICE is preferred in the majority of electrophysiology procedures and the remainder of this chapter will focus exclusively on this ICE modality.

STANDARD ECHOCARDIOGRAPHIC VIEWS

Right Atrium

The “home view” is obtained with the ICE catheter in the mid right atrium (RA) and the transducer in a neutral position facing the tricuspid valve (Figure 15.1, Panel A). It provides imaging of the RA, tricuspid valve, right ventricle (RV) and typically an oblique or short-axis view of the aortic valve.

From the “home view,” clockwise rotation of the catheter produces a long-axis view of the aortic valve and the RV outflow tract (Figure 15.1, Panel B). In this view, the cusp that is closer to the transducer is the noncoronary cusp and the opposite cusp is the right coronary cusp.

Additional clockwise rotation provides visualization of the mitral valve and the interatrial septum, with the left atrial appendage (LAA) anteriorly and the coronary sinus posteriorly (Figure 15.1, Panel C).

Further clockwise rotation allows imaging of the left atrial structures in the following sequence: first the left superior and left inferior pulmonary veins (Figure 15.1, Panel D), which often have a common ostium and are seen as a “pair of pants,” then the posterior left atrial wall and the esophagus, as well as the descending aorta, and finally the right inferior and right superior pulmonary veins (Figure 15.1, Panel E).

Further clockwise rotation allows visualization of the RA structures in the following sequence: first the posterior RA, and with gentle posterior deflection the superior vena cava, next the crista terminalis, and finally the RA appendage (Figure 15.1, Panel F) before continued clockwise rotation returns the imaging plane to the “home view.”

Right Ventricle

From the “home view” and maintaining continuous imaging of the tricuspid valve, the ICE catheter is anteriorly flexed and advanced into the RV. This produces a view of the inferior RV with the moderator band and the RV papillary muscles (Figure 15.1, Panel G).

From the RV view, gradual clockwise rotation provides a view of the interventricular septum (Figure 15.1, Panel H), then a long-axis view of the left ventricle (LV) showing the posteromedial papillary muscle, septal wall, and anterior wall (Figure 15.1, Panel I), and subsequently a view of the anterolateral papillary muscle, septal wall, and lateral wall (Figure 15.1, Panel J).

With additional clockwise rotation, the LV outflow tract comes into view, and with further rotation, a short-axis view of the aortic root is obtained (Figure 15.1, Panel K). Posterior to the aortic root, the LAA and the left superior pulmonary vein are visualized, separated by a ridge. From this view, advancement of the catheter will image a long-axis view of the RV outflow tract and the pulmonic valve (Figure 15.1, Panel L). Finally, continued clockwise motion will image the ascending aorta and then the lateral RV before returning to the initial plane view.

Figure 15.1 Standard ICE views obtained from the right atrium (Panels A–F) and from the right ventricle (Panels G–L).

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