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

• The presence of residual shunt is assessed after release.
• The relationship of the device to intracardiac structures should be carefully assessed before deployment.
• Assess for complications.

Transcatheter Closure of Muscular Ventricular Septal Defects

Technique

TEE generally provides the best imaging for percutaneous closure of muscular VSDs.

Step-by-Step Approach

1 Assess Anatomy

Percutaneous closure is possible for select muscular VSDs.

Key Points

• The location of the defect and size must be determined. The presence of additional defects and their relationship to each other is important. Due to the right ventricular trabeculations, any individual defect may have multiple channels on the right side of the septum (Fig. 3-4).
image

• The distance from the defect to the atrioventricular and semilunar valves should be measured.
image

Figure 3-4 Transesophageal four-chamber (4C) view of the ventricular septum (VS) can be used to identify the presence and location of muscular ventricular septal defects (VSDs) (arrows) (A). After device placement, the relationship of the right atrial disk (arrow) to the tricuspid valve (TV) is demonstrated (B). Color interrogation of the TV is performed to assess the presence and degree of regurgitation.

2 Device Placement

The device can be positioned with echocardiographic and fluoroscopic guidance, but only echocardiography can reliably visualize the ventricular septum (VS).

Key Points

• Echocardiography is helpful to assess whether the desired course across the VS has been accomplished. In the case of multiple channels or defects in the VS, successful device placement often requires placement within a particular channel or defect.
• Usually the left ventricular disk is deployed first. It needs to be visualized during deployment to confirm the location in the left ventricle without entrapment in the MV, including the MV apparatus.
• After the right ventricular disk has been deployed, the device is assessed to ensure adequate location of the device with the septum captured between the disks. The device size should also be assessed. The device size should be large enough so that the disks are larger than the diameter of the VSDs.
• It is important, particularly with high muscular defects, to ensure that the device does not interfere with the function of the aortic valve.

3 After Device Release

Echocardiography is key to assess the immediate results of device placement.

Key Points

• Device location is assessed in addition to residual shunt.
• The presence and size of additional defects are assessed. Large enough additional defects may necessitate the placement of additional devices.
• Assessment for complications should complete the examination.

Balloon Atrial Septostomy

Balloon atrial septostomy is often performed to improve mixing in patients with transposition of the great arteries. In this setting it can be done at the bedside with TTE guidance. A septostomy may also be required for palliation of other congenital lesions. Echocardiographic imaging can be used to assess the adequacy of the procedure.

Technique

TTE is usually adequate. On the rare occasion when atrial septostomy is performed in adult patients, TEE or ICE may be required.

Step-by-Step Approach

1 Assess Anatomy

The presence of inadequate atrial level communication is confirmed by echo.

Key Point

• The atrial septal anatomy is assessed to determine the location and size of the atrial level shunt.

2 Balloon Atrial Septostomy

Echocardiographic guidance is more than adequate to perform balloon atrial septostomy safely.

Key Point

• Imaging of the AS is required during catheter manipulation. A transthoracic four-chamber view provides adequate visualization so that the catheter tip can be placed in the LA. The balloon should be visualized during inflation. The relationship of the balloon to the MV, left atrial appendage, and PVs must be determined to minimize complications. Correct placement of the balloon in the LA must be verified before pulling the balloon through the AS (Fig. 3-5).
image

Figure 3-5 Transthoracic echocardiography (TTE) is adequate for guidance of balloon atrial septostomy in infants. The apical 4C view provides good visualization of both atria, the AS, and the mitral valve (MV). The balloon catheter tip (arrow) is seen before (A) and after (B) inflation. Confirmation of correct balloon position in the left atrium (LA) is crucial before pulling the balloon catheter. The ASD (arrow) is visualized after each septostomy to assess adequacy (C).

3 After Balloon Atrial Septostomy

Echocardiography confirms an increase in the size of the atrial communication.

Key Point

• The adequacy of the septostomy is assessed after each left-to-right pull. 2D and Doppler color assessment should be performed to determine the size of the enlarged atrial septal communication.

Balloon Mitral Valvuloplasty

Balloon mitral valvuloplasty is a much more common procedure in older patients with rheumatic MV disease. However, it may be useful for select patients with congenital MV stenosis.

Technique

TEE with general anesthesia provides the highest quality imaging. TTE can be used, but the quality of imaging is inferior to that of TEE. Fluoroscopy cannot be performed simultaneously with TTE without inadvertent radiation exposure to the sonographer. ICE can be used, but the image quality is inferior. Adequate images can be obtained if the catheter tip is positioned in the right ventricle.

Step-by-Step Approach

1 Initial Assessment

The primary use of echocardiography is to assess the efficacy of the procedure; and it allows early identification of complications.

Key Points

• The anatomy of the MV and mechanism of stenosis should be confirmed. Any mitral insufficiency should be quantified. The MV area can be measured (Fig. 3-6).
• The ideal candidate has stenosis at the level of the valve leaflets. The efficacy of balloon mitral valvuloplasty is less in the presence of a hypoplastic annulus or a double-orifice MV.
• Although rare, the presence of a left atrial thrombus should be excluded.
image

Figure 3-6 In children, TTE is often adequate to assess the MV during mitral valvuloplasty. Assessment should include two-dimensional (A) and color interrogation (B) of the MV (arrow). Three-dimensional echo (C) may provide more information about the MV leaflets (arrows) and mechanisms of stenosis or insufficiency.

2 Balloon Dilation

Echocardiographic visualization of the balloon during inflation is often helpful.

Key Points

• Echo can be used to monitor balloon positioning and visualize balloon inflation.
• The balloon should be positioned through the main orifice of the valve and not through the MV chordal attachments.

3 After Balloon Dilation

Echocardiography is used to assess the success of the procedure.

Key Points

• After each balloon dilation, the degree of mitral insufficiency should be quantified.
• The MV opening should be examined closely to assess commissural splitting.
• A comparison of valve area is often helpful.
• Hemodynamic data are very difficult to interpret because the MV gradient is dependent on preload and cardiac output.

4 Detection of Complications

Echocardiography is used to identify complications.

Key Points

• Hemopericardium can be secondary to transseptal atrial catheterization or wire puncture. Echocardiographic guidance can be used to perform pericardiocentesis.
• Severe mitral regurgitation (MR) is identified by echocardiography.

Transcatheter Aortic Valve Implantation

Transcatheter aortic valve implantation is an investigational technique.

Technique

TEE is the most common technique used for transcatheter aortic valve placement. TTE can be used if there is a contraindication to general anesthesia.

Step-by-Step Approach

1 Assess Anatomy

Accurate assessment of aortic valve anatomy is dependent on echo.

Key Points

• The aortic valve annulus should be measured. Accurate measurement of the annulus is a crucial component of valve sizing.
• The aortic valve anatomy (tricuspid) should be assessed and any calcifications identified.
• The aortic root dimensions should be measured.
• Left ventricular size and function should be assessed.
• The MV anatomy should be determined and any insufficiency quantified.
• If an apical approach is used, echocardiography can identify the left ventricular apex for determining the surgical incision site.

2 During the Procedure

Echocardiography can be used to confirm correct wire placement and balloon position during dilation (Fig. 3-7A).

image

Figure 3-7 A, Long axis view by transesophageal echocardiography (TEE) of deployment of percutaneous aortic valve replacement. The delivery balloon is inflated in the left ventricular outflow tract across the stenotic aortic valve. Note the rapid heart rate reflecting rapid ventricular pacing needed to deploy the valve in a stable position. B, TEE short axis of the deployed aortic valve. The valve leaflets are closed, and the stent is seen across the aortic annulus.

Key Points

• Echocardiography is important during wire placement. The wire course should be carefully visualized. The relationship of the wire to the MV apparatus is important. The wire course should be free of the MV apparatus.
• Echocardiography can be used for balloon positioning during the aortic valvuloplasty and then to assess the presence and extent of aortic insufficiency.
• Valve placement can be assessed to ensure correct location of the device during deployment.

3 After Deployment

Echocardiography is crucial to the assessment of the valve after deployment (see Fig. 3-7B).

Key Points

• The position of the valve in relation to the aortic annulus is identified.
• Valve function is assessed for stenosis or insufficiency.
• Aortic valve insufficiency can be assessed to quantify the extent and determine the location of the regurgitant jet. There is often a small amount of regurgitation associated with the wire. Assessment should be performed both before and after wire removal.
• The presence and extent of paravalvular leaks should be identified. The device should be evaluated for incomplete expansion or malposition (Box 3-1).

Box 3-1

Role of Echo in Interventional Catheterization

1 Echo is a crucial adjunct to fluoroscopy for many complex interventional catheterization procedures.
2 High-quality imaging is important.
3 The echocardiographer needs good knowledge of the procedure.
4 A team approach is required with good communication between the echocardiographer and the interventional cardiologist.
5 The choice of technique (TTE, TEE, or ICE) depends on the procedure and whether general aesthesia is needed.

Suggested Reading

1 Hellenbrand WA, Fuhey JT, McGowan FX, et al. Transesophageal guidance of transcatheter closure of atrial septal defect. Am J Cardiol. 1990;66:207-213.

2 Hijazi ZM, Shivkumar K, Sahn DJ. Intracardiac echocardiography during interventional and electrophysiological cardiac catheterization. Circulation. 2009;119:587-596.

3 Kim S, Hijazi ZM, Lang R, et al. The use of intracardiac echocardiography and other intracardiac imaging tools to guide non-coronary cardiac interventions. J Am Coll Cardiol. 2009;53:2117-2128.

4 Moss RG, Ivens E, Pasupati S, et al. Role of echocardiography in percutaneous aortic valve implantation. J Am Coll Cardiol Imaging. 2008;1:15-24.

5 Mullen MJ, Dias BF, Walker F, et al. Intracardiac echocardiography guided device closure of atrial septal defects. J Am Coll Cardiol. 2003;41:285-292.

6 Perk G, Lang RM, Garcia-Fernandez MA, et al. Use of real time three-dimensional transesophageal echocardiography in intracardiac catheter based interventions. J Am Soc Echocardiogr. 2009;22:865-882.

7 Silvestry FE, Kerber RE, Brook MM, et al. Echocardiography-guided interventions. J Am Soc Echocardiogr. 2009;22:213-229.

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