Echocardiography in the Cardiac Catheterization Laboratory

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3 Echocardiography in the Cardiac Catheterization Laboratory

Troy Johnston

Background

Interventional catheter techniques are now well established for the treatment of congenital heart disease (CHD). Echocardiography is an essential adjunct to fluoroscopy during certain interventional catheterization techniques. The improved imaging resulting from the addition of echocardiography may lead to increased procedure success with improved safety and decreased fluoroscopic time. Procedures include transcatheter closure of atrial septal defects (ASDs), patent foramen ovale (PFO), and ventricular septal defects (VSDs), balloon atrial septostomy, balloon mitral valvuloplasty, and percutaneous aortic valve replacement. Echocardiography is used to assess the anatomy, guide the procedure, and assess the immediate result. The techniques used include transthoracic echocardiography (TTE), transesophageal echocardiography (TEE), and intracardiac echocardiography (ICE).

Cooperation and clear communication between the proceduralist and the echocardiographer are essential. All team members need to understand the procedural and imaging requirements for technical success.

Echocardiographic Techniques

Multiple echocardiographic techniques are used during interventional procedures. The choice of technique is determined by technical issues associated with the modality, experience with the technique, and the use of general anesthesia.

The simplest technique is TTE. The supine position of the patient and the fluoroscopic imaging equipment may increase the complexity of image acquisition. Careful attention is required in order not to contaminate the sterile field. Despite these limitations, this technique is capable of providing good-quality imaging.

TEE provides excellent imaging and is the standard technique for most centers. This technique usually requires general anesthesia.

ICE uses an ultrasound catheter that is steerable and deflectable. The most commonly used catheter (AcuNav catheter; Biosense Webster, Diamond Bar, CA) comes in 8- and 10-French sizes. It has a 64-element vector phased-array transducer (5.5–10 MHz) at the tip of the catheter. It produces a two-dimensional (2D) sector of 90 degrees with color Doppler imaging. ICE can be performed by the interventionalist without the need for an echocardiographer. The greatest limitation of this technique is the catheter cost.

Real-time three-dimensional (3D) echocardiography is a more recently developed technique that can be used to image the anatomy, catheters, and devices. It allows for improved understanding of the relationships between the device and cardiac structures. The image quality and resolution are inferior to those of the other 2D techniques (Table 3-1).

TABLE 3-1 ADVANTAGES AND LIMITATIONS OF EACH TECHNIQUE

image

Transcatheter Closure of Atrial Septal Defects/Patent Foramen Ovale

Technique

TEE is most often used. It provides excellent image quality. ICE provides comparable image quality without the need for general anesthesia.

Step-by-Step Approach

1 Assess Anatomy

Secundum ASDs and PFO are amenable to transcatheter closure.

Key Points

• Before closure attempt, the anatomy of the atrial septum (AS) is assessed. Morphology, maximum diameter, defect number, total septal length, adequacy of the rims, and distance of the defect from the surrounding structures must be determined (Fig. 3-1).
• The assessment for a PFO should include the length of the tunnel and the assessment of an associated atrial septal aneurysm. An intravenous injection of agitated saline solution bubbles is performed to identify the presence of a right-to-left shunt.
• The Eustachian valve should be assessed. A large Eustachian valve or Chiari network does not preclude the ability to place a device.
• Color Doppler should be performed to assess for additional defects and the presence of fenestrations.
• The devices that are currently available are indicated for secundum ASDs and PFO. The exact location of the defect needs to be determined.
• The pulmonary veins (PVs) should be assessed. The presence of partial anomalous pulmonary venous return may indicate surgical referral to address both anomalies.
• The entire rim needs to be assessed. The presence of a circumferential rim of at least 5 mm is ideal for closure. The exception is the retroaortic rim. Deficiency of the retroaortic rim does not preclude device placement.
image

Figure 3-1 Transesophageal echocardiographic evaluation of the atrial septum (AS) includes measurement of the atrial septal defect (ASD) diameter (A), septal rims (B), and the total septal length (C).

2 Dynamic Sizing

A sizing balloon is often used to measure the stretched diameter of the ASD.

Key Points

• Color Doppler assessment is performed during balloon inflation. Careful attention is paid to the point at which any left-to-right flow is eliminated. The diameter of the balloon is measured at this stop-flow diameter. The narrowest diameter, or waist, in the balloon is measured (Fig. 3-2).
• This diameter is used for device sizing. Different devices have different sizing guidelines.
image

Figure 3-2 Intracardiac echocardiography (ICE) image of a sizing balloon straddling the AS. The waist of the balloon (arrows) is measured at the point where the left-to-right atrial shunt ceases. Note that the color box is larger than the balloon at the level of the AS.

3 Device Placement

Live imaging during device placement is required to assess the relationship of the device to cardiac structures.

Key Points

• The left atrial disk of the device is deployed first. A view with good visualization of the mitral valve (MV) and AS is required. The left atrial disk should be free in the left atrium (LA) during extrusion from the sheath. It should not be opened in the PVs, left atrial appendage, or MV.
• After the device has been fully deployed, echocardiography should determine whether all the rims have been captured. Often the interventional cardiologist will need to “wiggle” the device to help visualize the rims within the space between the right and left disks.
• The relationship of the deployed device to the MV, pulmonary venous return, and superior vena cava (SVC) is important before final release of the device (Fig. 3-3). Any interference with these cardiac structures most often is an indication for device removal.
image

Figure 3-3 ICE image of an Amplatzer septal occluder before release from the delivery cable (arrow) with tension on the right atrial disk (A). The superior vena caval flow is unobstructed by the Amplatzer septal occluder (B). After release of the device, the right atrial disk rests flush against the right side of the AS (C).

4 After Device Release

Complete assessment of the device is performed after device release.

Key Points

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