Echocardiography for interventions in the cardiac cath lab

With the continued advances in the field of interventional cardiology and new innovative therapies for structural heart diseases, echocardiography (transthoracic echocardiography and transesophageal echocardiography) imaging has become an important modality for the cardiac cath lab.

In this brief review, we will discuss the use of echocardiography for some of the most useful and newest interventions in the cardiac cath lab: atrial septal defect (ASD) closure, alcohol septal ablation for hypertrophic obstructive cardiomyopathy, left atrial appendage occlusion, transcatheter aortic valve implantation and percutaneous mitral repair for severe mitral regurgitation.

Percutaneous ASD closure

Although transthoracic echocardiography (TTE) has a critical role in helping to determine the presence of an ASD, transesophageal echocardiography (TEE) is critically important to determine the type of ASD (primum; sinus venosus — both superior and inferior; and secundum), as well as to determine whether there are multiple fenestrations present. TEE also can be used to evaluate anomalous pulmonary venous return and the adequacy of margins of the secundum ASD (superior, inferior, anterior and posterior) — things that are critical for proper deployment of the ASD closure device (see figure 1, 2). The ASD should have more than three sufficient rims (meaning at least 5 mm) including the necessity to have a sufficient superior rim.

Stamatios Lerakis

Randolph P. Martin

TEE, especially real-time 3-D TEE, is important for not only determining the type of ASD and the adequacy of rim but for accurate measurement of ASD size, which is critical to determine if the defect can be closed percutaneously. Also important is to evaluate the margin of the ASD in relation to the surrounding structures, such as atrioventricular valves, coronary sinuses, right upper pulmonary vein, as well as the inferior vena cava and superior vena cava (see figure 3).

During the procedure, TEE is extremely important for determining the size of the device that can be used, as well as guiding delivery, aiding in deployment and potentially detecting complications. The size of the closure device should be at least 1 mm to 2 mm larger than the ASD measured by echocardiography, as long as sufficient rim is present.

Figure 1 All images courtesy of: Stamatios Lerakis, MD

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Alcohol septal ablation

TTE is important for selecting the appropriate patients for this procedure: resting or provocable gradient through the left ventricular outflow tract of 50 mm Hg, minimal septal thickness of 18 mm, absence of coexistent mitral or aortic valvular disease, and absence of abnormal subaortic apparatus.

TTE, along with myocardial contrast echocardiography (MCE), are critical for helping to delineate the vascular distribution of the various septal perforating branches of the left anterior descending coronary artery. By using myocardial contrast injection, the septal perforating branch that supplies the area of the proximal hypertrophied septum — at the point of maximum systolic anterior motion of the mitral leaflets and associated septal contact — is critical. This is the area that can be best ablated using the alcohol injection. Because of the variable perfusion of the septum by septal perforators, use of echocardiography with MCE will help to avoid either ablation of too large a portion of the septum (it could lead to a major complication) or the wrong portion of the interventricular septum.

Both before and after alcohol septal ablation, the resting and provocable dynamic LV outflow tract gradients can be measured, and if after the first procedure significant gradients persist, repeat alcohol septal ablations can be performed under echocardiography guidance.

Again, it is emphasized that the use of MCE is critical to make sure that the right septal perforator is chosen to which the alcohol for ablation will be delivered. Major complications could occur if the right side of the septum is ablated or a lower portion of the ventricular septum is ablated — a portion that is not responsible for the dynamic outflow tract obstruction.

Left atrial appendage occlusion devices

Two left atrial appendage occlusion devices have been tested in the PLAATO and WATCHMAN trials for patients with no valvular atrial fibrillation as an alternative to anticoagulation with warfarin (Coumadin, Bristol-Myers Squibb). TEE is critical for this procedure because it can exclude those patients who should not be considered for left atrial appendage occlusion — meaning those with left atrial appendage thrombi or significant smoke or when the anatomy of the left atrial appendage is not amenable to closure by a device. TEE during the procedure is critical for guiding the delivery and deployment of the occluding devices in the cath lab.

TEE is important for guiding the transeptal puncture of the guiding catheter for positioning the device into the left atrial appendage, making sure that the surface of the closure device is distal to the ostium of the left atrial appendage in a 180° sweep (not protruding in the left atrium), confirming that all the left atrial appendage lobes are sealed and making sure there is no significant flow around the device before the device is released (see figure 4).

Percutaneous aortic valve replacement

Echocardiography plays an important role for the evaluation of the eligibility of patients for percutaneous transfemoral or transapical aortic valve replacement. Measurement of the aortic annulus by TEE is a critical part of the procedure to select the one of two available valves offered today through the Partner Trial (Edwards Valve 23 mm and 26 mm).

TEE in our experience is important for assisting the interventional cardiologist, to deliver the mounted valve on a balloon delivery catheter, to confirm coaxially of the delivery system with the LV outflow tract and proximal aorta and to position the valve so the aortic end can be aligned with the tips of the native aortic valve leaflets. It is also important to deploy the valve, to evaluate for valvular and paravalvular aortic regurgitation post-deployment and to detect and assist in dealing with possible complications such as valve embolization (see figure 5 showing the aortic valve with severe stenosis and figure 6 showing the new aortic valve after percutaneous replacement).

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Percutaneous mitral repair for severe mitral regurgitation

A mitral clip delivered percutaneously to repair severe mitral regurgitation is based on the Alfieri Stitch, a surgical edge-to-edge mitral repair. The mitral clip by approximating the midsections of the middle scallops of the anterior and posterior mitral leaflets creates a double orifice, potentially eliminating the severity of the mitral regurgitation. This technique has been tested in the EVEREST trial. TEE is not only important for identifying the eligible patients to receive the mitral clip but also is the imaging modality for guiding the procedure of delivering the clip.

TEE is important for guiding the transeptal puncture of the delivery catheter (an important step of the procedure), steering the catheter from the left atrium toward the mitral apparatus and positioning the catheter and clips not only strictly perpendicular to the leaflets (90º for the commissural edge) but directly opposite A2 and P2 scallop level (ie, in the midportion of the orifice). TEE is also important, not only for making sure that the device is well seated but for evaluating the degree of residual mitral regurgitation that is present from the created double orifice. Additionally, making sure that the device is well positioned and that there is no significant mitral inflow tract stenosis is critical before release of device (see figure 7).

Randolph P. Martin, MD, is an Associate Dean of Clinical Development and Professor of Medicine at Emory University School of Medicine and is a member of the Imaging Section of the Cardiology Today Editorial Board.

Stamatios Lerakis, MD, is Associate Professor of Medicine (Cardiology) and Radiology at Emory University School of Medicine.