Intraprocedural Echocardiographic Guidance for Transcatheter Interventions in Aortic and Mitral Position

Chirojit Mukherjee

INTRODUCTION

Transcatheter interventions are viable option in patients suffering from a stenotic or incompetent valve and had been denied surgery (1). These patient subsets are presently well defined and confined to the elderly high-risk patient population. However, based on individual registries and on initial results from ongoing trials, there is a trend to deploy the valves in the intermediate and low-risk population. With the concept of “heart team” approach and methodical patient selection criteria and detailed procedure planning the outcomes are predictable. The routine use of the “heart team” for transcatheter interventions has become the standard practice and recommended by AHA/ACC and ESC guidelines (2).

Although these procedures are mostly performed in hybrid operating rooms or modified cath labs, there is an imperative need for intraoperative multimodal imaging. This chapter highlights the importance of intraoperative echocardiography during catheter-based interventions in routine clinical practice.

TRANSCATHETER AORTIC VALVE REPLACEMENT

Current Devices

There are eight transcatheter aortic valve replacement (TAVR) systems currently available in Europe (as shown below). The first two devices have been approved by the U.S. Food and Drug Administration (FDA) for usage in the United States (Fig. 16.1).

There is limited scope in this chapter to describe all the valves and their delivery systems. However, these newer devices are all advantageous in comparison to their previous models. The manufacturers are designing the valves and delivery system to:

Facilitate ease of delivery and deployment
Low-profile valves providing better hemodynamics
Miniaturization of catheter and delivery system leading to reduced vascular complications
Catering to both small and large aortic annulus diameters owing to increased availability of wide-ranging valve and device sizes
Valve and delivery system aiming toward ability to retrieve and reposition, thereby improving accuracy of valve positioning
Modification of valve designs to prevent/reduce paravalvular regurgitation
Designing of valves meant for specific indication and tailored approach

Procedural Performance (TAVR)

Transapical Aortic Valve Replacement

This approach is through the left ventricular (LV) apex via a left anterior thoracotomy incision. After insertion of rescue access (guidewires and sheath for emergency initiation of CPB), an aortic root pigtail catheter is placed in the ascending aorta. Fluoroscopy is used to determine aortic root disease, cusp and root anatomy, and ascending aortic dimensions. The apex of the heart is prepared with purse-string/mattress sutures, and bipolar epicardial pacing wires are placed for rapid ventricular pacing (RVP) required during valve implantation. Apical access is established and guidewires are placed and subsequently exchanged with an apical sheath and balloon valvuloplasty catheter. The newer-generation valve may preclude balloon aortic valvuloplasty (BAV) but is usually performed using RVP (usually 180 to 200 beats/min) in patients with bulky calcification of the aortic valve. Thereafter the apical sheath is withdrawn, and the valve delivery system is introduced through the LV apex. After correct valve position is confirmed by fluoroscopy and transesophageal echocardiography (TEE), a second episode of RVP facilitates valve implantation. Optimal positioning and valve deployment are then achieved using either fluoroscopy or TEE (3,4).

FIGURE 16.1 A: Sapien 3 valve (© 2019 Edwards Lifesciences LLC, Irvine, CA. All rights reserved. Edwards, Edwards Lifesciences, CardiAQ, CardiAQ-Edwards, Fortis, Edwards SAPIEN, SAPIEN, SAPIEN XT and SAPIEN 3 are trademarks of Edwards Lifesciences Corporation). B: CoreValve Evolut R (CoreValve^TM Evolut^TM R. Reproduced with permission of Medtronic, Inc.). C: ACURATE neo valve (©2019 Boston Scientific Corporation or its affiliates. All rights reserved). D: Portico^TM transcatheter aortic heart valve (Portico is a trademark of Abbott or its related companies. Reproduced with permission of Abbott, © 2019. All rights reserved). E: Engager valve (Engager^TM valve. Reproduced with permission of Medtronic, Inc.). F: LOTUS Edge^TM Aortic Valve System (©2019 Boston Scientific Corporation or its affiliates. All rights reserved).

Transfemoral Aortic Valve Implantation

The transfemoral approach is considered in patients when the anatomy of the iliac vessels is favorable for the insertion of the delivery system. Femoral access is achieved using the contralateral approach and multiple progressive dilatations may be required to accommodate the large deployment sheath, which is then fixed in place with a stay suture. With the iterations leading to miniaturizations of device and delivery systems, this may no longer be required. A pigtail catheter is placed in the abdominal aorta for continuous arterial monitoring and angiographic facilitation of the anatomy of iliofemoral vessels. Pacing leads may be inserted via the
internal jugular or femoral veins, depending on the choice of valve. After guidewire insertion, a 14-Fr sheath is introduced. A J-tip guidewire is positioned across the native aortic valve and is then replaced with an Amplatz Super Stiff (260-cm) guidewire. The delivery system along with the crimped valve is directed toward the annulus of the native valve using fluoroscopic guidance. After satisfactory positioning using central and coaxial orientation, valve deployment is performed. Correct positioning is achieved by full root angiographic evaluation. After satisfactory implantation of the valve, the delivery system along with the guidewire is withdrawn, femoral access is repaired, and a pressure bandage is applied (5,6).

Transaortic Approach

In this retrograde access, the valve is employed through a ministernotomy incision or a right minithoracotomy. Both self-expanding and balloon-expandable valves have been deployed using this method. This approach offers the surgeon easier manipulation and better control of the valve delivery system. Postoperative pain control is better due to a smaller incision compared to transapical access (7).

Key Points and Practical Approach

Procedural Considerations

With the standardization of procedures, diminishing intraoperative complications and surgeons/cardiologists/anesthesiologists having achieved their “learning curve,” there is an evolving inclination to perform the TAVR under “minimalist” approach (8). This resorts to the use of monitored anesthetic care (MAC), using local anesthesia and transfemoral access and eliminating TEE guidance during the procedure (9). These patients usually undergo enhanced recovery protocol with reduced length of stay (LOS) in the hospital. Simultaneous development of a “hybrid” strategy has evolved, whereby the careful selection of patients subjects them to either TTE with MAC or TEE with general anesthesia.

The comparisons of both the echocardiographic methods are shown in Table 16.1. In complex procedures where valve sizing is difficult, in patients allergic to contrast agents or with compromised renal function, and in those with predictable intraoperative complications (e.g., low-lying coronaries), TEE with general anesthesia is preferred (10).

TABLE 16.1 Comparison of Intraoperative Imaging With TTE and TEE

Advantages	Disadvantages
▪ Intraoperative Imaging With TTE
Monitored anesthesia care (MAC)	Intraoperative image quality may be compromised
Beneficial tool for preoperative assessment	Needs to be performed in sterile field, leading to frequent delays in procedural performance
Predefined standard views for assessment of the heart	Image acquisition is limited with low resolution and low frame rates compared to TEE
Easy availability for intraoperative use	Frequent interruption during image acquisition during the procedure
Early recovery and reduced length of stay (LOS) in hospital
▪ Intraoperative Imaging With TEE
Requires GA or MAC, so probe manipulation is easier	Probe manipulation may be continuously required and can interfere with angiogram images
Early detection of periprocedural complications	As a semi-invasive method, trauma to esophagus and surrounding anatomical structures is possible
Imaging possibility during the entire procedure	Image quality can be compromised due to heavy calcification causing acoustic shadowing
High resolution and high frame rates for 2D/3D TEE	Performing TEE in local anesthesia and conversion during emergency can be challenging
Postoperative assessment can be done in the operating room	Periprocedural costs may be higher and additional setup is required

FIGURE 16.2 Septal calcification, especially in vicinity of low-lying coronary ostium, may lead to sudden occlusion post BAV or after valve deployment.

Preoperative Assessment

The aortic valve symmetry, localization, and severity of calcification are important preoperative information to evaluate for successful valve deployment. This is a critical first step before commencing with TAVR, as faulty measurements can lead to serious complications. The TAVR valves are sutureless and hence need an anchoring sheath or landing zone to prevent the valve from being dislodged. The heavily calcified and stenosed native valve provides the ideal environment and facilitates implantation. Unfortunately, bulky and eccentric calcification poses an increased risk for a paravalvular leakage (11). While standard multiplane TEE can be used to measure the annulus, real-time three-dimensional transesophageal echocardiography (RT-3D TEE) in a biplane mode provides simultaneous long-axis (LAX) and short-axis (SAX) views of the valve and annulus, which may improve the accuracy of these measurements. The observer starts from the ME AV LAX view, placing the cursor in the middle to transect the aortic valve. With RT-3D TEE, the biplane view is used to generate the corresponding SAX view ME AV SAX in the orthogonal plane. The ME AV SAX view should demonstrate all three commissures along with the base of any calcified leaflet, which further ensures a true SAX plane. This should ascertain whether the calcification is symmetric, asymmetric, or the presence of a bicuspid valve

(Videos 16.1 to 16.3). Further the presence of calcified plaques overlying the coronaries

(Video 16.4) can be preoperatively diagnosed (Fig. 16.2).

The annulus of the aortic valve and aortic root is then measured in the LAX and SAX in systole

(Video 16.5). With standard two-dimensional (2D) TEE, the annulus is generally measured from the ME LAX view, within the SAX plane by rotating the plane to ˜40° to 50° (12). To avoid underestimates of annual size, it is important to identify the true annulus, rather than the common overlying calcification. Measurements (trailing edge to leading edge) are made in systole at the AV leaflet insertion sites (hinge points) within the LV outflow tract (LVOT) (Fig. 16.3) (13).

FIGURE 16.3 Annulus can be reliably measured using biplane technique. The measurements are done at hinge points in left ventricular outflow tract from trailing edge to leading edge.

Alternatively, the annulus can be measured postprocessing using commercial software from a full 3D volume data set obtained in the ME AV LAX view, but owing to time constraints in the operating room, this currently is more for research purposes (14). In the future, improvements in automated 3D echo processing should allow rapid extraction of annular anatomy.

Also, it is important to exclude low-lying coronaries, which increase the risk of coronary occlusion (15). Whether the prophylactic placement of a guidewire is necessary can be decided preoperatively using TEE.

Following TAVR placement, a comprehensive evaluation (15) is necessary to rule out new regional wall motion abnormalities (RWMAs), and to exclude the presence of an LV or left atrial (LA) thrombus.

Intraoperative Guidance

Guidewire Placement

When performing TAVR via a transapical approach, TEE-guided digital palpation by the surgeon can preclude false puncture of the LV. The passage of the guidewire from the LV apex to the ascending aorta is observed in RT

(Video 16.6). Transaortic or transfemoral access can also be confirmed by TEE visualization of the guidewire in the LV through retrograde access.

TEE checklist to diminish complications:

Nonapical puncture (use guidance through digital palpation of LV apex)
Follow guidewire to prevent entanglement of the wire in secondary chordae of mitral valve (MV) (Video 16.7)
Guidewire not aligned with AV (stuck in MV or entry into LA) or through septal hypertrophy (Videos 16.8 and 16.9)

Balloon Aortic Valvuloplasty

Although the “minimalist” approach eliminated valvuloplasty pre-TAVR, it is useful to increase the leaflet excursion and generate adequate output before BAV. Biplane TEE imaging is helpful as the balloon is positioned midvalve, for universal and complete dilation of the calcified valve

(Video 16.10). The presence of asymmetric calcification as opposed to regular calcification may predispose for postimplantation paravalvular leak. The valvuloplasty can be also used for confirmation of the annulus size and displacement of
calcium during valve deployment. Rupture or sliding of the balloon during valvuloplasty due to uncoordinated pacing necessitates another episode of valvuloplasty with a larger balloon before valve implantation. Balloon valvuloplasty may cause aortic regurgitation, which may necessitate rapid valve deployment

(Video 16.11).

FIGURE 16.4 The crimped Sapien valve before deployment is imaged in this figure. The arrow on the left of the picture shows the distal end of the valve whereas the arrow on the right demonstrates the tip of the delivery system.

TEE checklist to diminish complications:

Check for septal calcification or calcified plaques in the proximal left main or right coronary arteries prior to BAV (Video 16.12)
Pattern of calcification: symmetric or asymmetric
Rupture or sliding of the balloon during BAV

Valve Positioning and Implantation

Fluoroscopic imaging with contrast agents is primarily used for valve positioning and deployment. However, in patients with bulky or limited calcification, TEE is complementary during the procedure. Inadequate deairing of applicator device may lead to occlusion of the coronaries during valve implantation

(Video 16.13). The newer-generation balloon-expandable valve could be deployed without significant oversizing and the valve is designed to shorten, during deployment, only from the ventricular side. Hence the tip of the valve should be placed below the sinotubular junction. Biplane imaging may be helpful to coordinate the position of the valve in relation to the left main coronary artery. RT-3D TEE imaging allows depth perception which cannot be appreciated in 2D mode (Fig. 16.4).

The newer-generation self-expandable valves are mostly deployed under fluoroscopic guidance. When implanting a self-expandable valve, TEE should confirm that the nitinol stent is well within the borders of the calcified native annulus

(Video 16.14). The fluoroscopic views may sometimes be obstructed by the TEE probe in the esophagus and hence may need to be frequently withdrawn into the upper esophagus. Alternatively, another angulation of LAO/caudal positioning of fluoroscopic image may be used to facilitate simultaneous

TEE guidance during deployment.

TEE checklist to diminish complications:

RWMA after deployment due to coronary occlusion (Video 16.15) or air entrapment in the coronaries (Video 16.16)
Aortic root dissection (Video 16.17)
Valve migration (Video 16.18)
Newly diagnosed mitral or tricuspid regurgitation

FIGURE 16.5 Biplane views allow rapid assessment of the newly implanted valve. Color Doppler identifies the quality of replacement.

Echocardiographers involved in implantation guidance need to familiarize themselves with the structure of the implantable valves and their delivery systems to ensure that the necessary landmarks are identified during the procedure. During implantation, the status of the MV also needs to be considered. The applicator device can obstruct, distort, or perforate the anterior mitral leaflet causing severe regurgitation leading to rapid deterioration in hemodynamics (Video 16.19).

Postoperative Assessment

After TAVR, immediate evaluation of the replaced AV is required.

Confirm Position, Function, Gradient, and Leaks

Owing to the absence of suture rings, the transcatheter valves usually have larger valve areas. The ME AV LAX and ME AV SAX views (ideally in combination using biplane views) are observed to assess how well the valve is seated and to rule out the presence of para/transvalvular leak (Fig. 16.5,

Videos 16.20 and 16.21).

If valvular regurgitation is present, the guidewire may be withdrawn for a second assessment. Typically, the leaflet’s seating improves over the first few minutes following implantation, and the valvular regurgitation will lessen. The TG LAX and deep TG views are used to measure the postimplantation gradient and to determine the severity of any regurgitation (Fig. 16.6,

Video 16.22A,B).

Assessment of Paravalvular Leaks

Even after using the Valve Academic Research Consortium (VARC) criteria for assessment of AR (16), this can be sometimes challenging. Color Doppler imaging in both SAX and LAX views of the aortic valve should be assessed, as regurgitant jets can occur around the perimeter of the valve. Owing to the atypical nature of the jets (eccentric/multiple), color flow Doppler is more beneficial in localizing (extent and origin) and assessing (multiple, width, eccentric, central, peripheral, single) the jets compared to typical Doppler parameters (qualitative and semi-quantitative). Quantitative Doppler (ERO and EROA) and 3D color Doppler planimetry of the vena contracta may prove helpful, although tedious to perform in the operating room

(Video 16.23).