Intracardiac Echocardiography

Frank E. Silvestry, Susan E. Wiegers

• Publisher: CRC Press
• Year: 2021
• ISBN:
  9781000144482
• Edition: 1
• Topic: Medicine
• Subtopic: Medical Theory, Practice & Reference

Intracardiac Echocardiography is the first echocardiographic textbook of its kind to specifically cover ICE. Discussing all aspects of intracardiac ultrasound, it allows readers to perfect ICE image acquisition and helps to guide interpretation of this information during interventional and electrophysiologic procedures.

Unique and informative, the text explores:

• introductory echo physics
• currently available intracardiac ultrasound systems
• basic image acquisition
• the role of ICE in both the interventional and electrophysiology laboratory, as well as in the diagnostic setting.

Featuring expert commentary by leaders in the field, the book also includes high quality echocardiographic images illustrating how ICE is used in a wide variety of procedures such as transseptal catheterization, PFO and ASD closure, atrial fibrillation ablation procedures, and many others.

1

Why intracardiac echocardiography?

Frank E Silvestry and Susan E Wiegers

Introduction

Intracardiac echocardiography (ICE) is a new ultrasound modality used to guide a variety of percutaneous non-coronary interventional and electrophysiologic procedures. As more complex procedures are undertaken percutaneously, real-time echocardiographic guidance has become an essential aspect of their successful performance, by both improving procedural outcomes and reducing risk.^1,2 Prior to the development of ICE, fluoroscopy and selective angiography were used for procedural guidance in the catheterization and electrophysiology laboratories, but with significant limitations. Fluoroscopy cannot identify the anatomic ‘targets’ of procedures, such as the interatrial septum, foramen ovale, cardiac valves, coronary sinus ostium, vena cava, atrial appendages, crista terminalis, Eustachian ridge, and pulmonary veins. While selective angiography may identify some of these structures, the spatial relationship between structures, particularly in different chambers cannot be clearly delineated. Furthermore, angiography requires the use of radiographic contrast agents with the attendant risks, and cannot easily be performed continuously during an interventional procedure. Finally, the three-dimensional anatomy of structures such as the mitral valve and fossa ovalis are difficult to delineate without multiple biplane images, and therapeutic devices must be deployed in a precise anatomical fashion for proper function.

Intracardiac echocardiographic guidance allows assessment of anatomy and monitoring of the catheter delivery systems including guide-wire, delivery sheath, and balloon or closure device. Most importantly, the relative position of the catheters to the target anatomic structures, the position of catheter contact, and presence and size of ablation lesion are easily determined. In addition, as continuous on-line imaging is used, procedural complications such as thrombus and char formation, and pericardial effusion can be promptly detected. This chapter will review the history of intracardiac echocardiography, and provide an understanding as to why this technology is being used increasingly in the catheterization and electrophysiology laboratory settings. Chapter 2 will review the basics of ultrasound imaging for those intracardiac echocardiographic operators who have not had substantial ultrasound experience.

History of ICE

The first catheter-mounted ultrasound transducer was described by Cieszynski in 1960.³ Further reports of transducers intended for intracardiac use utilizing M-mode ultrasound displays followed in the late 1970s and early 1980s.^4,5 The first catheter-based two-dimensional ultrasound systems were introduced in the 1980s, and were intended for intracoronary imaging.^5,6,7 These early devices used high-frequency transducers (20–40 MHz) that were ideally suited to imaging small structures such as the coronary arteries, however their limited depth of penetration made them unsuitable for imaging larger intracardiac structures. The introduction of lower-frequency catheters (12 MHz or less) in the 1990s made intracardiac imaging possible.^7,8,9,10,11 Early experimental and clinical studies demonstrated that these devices could monitor left and right ventricular function, delineate complex anatomy, guide transseptal punctures, and biopsy of cardiac masses.^{5,6,8,10, 11,12,13,14,15,16,17,18,19,20,21,22,23,24,25}

Continued transducer technological development has allowed for the use of these catheters in a wide variety of clinical settings. Initially their use was limited to defining coronary and peripheral vascular anatomy, and in the guidance of vascular interventions. However, they are now used for a broad range of clinical applications. These include the guidance of interventional cardiology and electrophysiologic procedures, the evaluation of right and left ventricular function, evaluation of the cardiac valves, and of the aorta. Diagnostic ICE offers the image quality comparable to transesophageal echo (TEE) in those with a contraindication to TEE, and additionally may be able to visualize structures that are typically not well seen by TEE. In the intensive care unit, diagnostic intracardiac echocardiography offers the prospect for prolonged imaging of the heart that is comparable to TEE, in a manner that may be better tolerated than prolonged esophageal intubation.

Ultrasound catheter types

The two most popular types of intracardiac ultrasound catheters available for clinical use today are the mechanical (rotational) and phased array transducers. The mechanical transducer is similar to that used for intravascular ultrasound (IVUS), with a rotating ultrasound transducer driven by a motor unit at the opposite end of the drive shaft, and produces a 360° ‘radial’ view that is perpendicular to the plane of the catheter. Radial images are presented in a cross-sectional imaging context. The second type is a fixed or phased array catheter-mounted transducer that produces the ultrasound sweep electronically. The resultant image is a wedge-shaped image sector similar to that of transthoracic or transesophageal echo probes. Phased array transducers present images in a longitudinal context. Both types of catheters provide high-resolution, real-time images of anatomic structures and of other intracardiac devices and catheters. These catheters are currently 8–10 French in size, and are typically introduced through a sheath in a femoral or jugular veins. Phased array catheters offer a larger depth of field, include Doppler imaging capabilities, and generally greater maneuverability. Mechanical catheters on the other hand, offer excellent near-field resolution and outstanding near-field image quality, however these catheters are stiffer and have less maneuverability due to the required high-speed rotating core.

Available ultrasound systems

There are three currently commercially available ICE systems. Each has unique features and advantages. The Boston Scientific UltraICE system utilizes a radial ICE imaging transducer, is not steerable, and is presently limited to 2D (two-dimensional) imaging. Both Siemens AcuNav and the newer EP Medsystems ImageMate use phased array transducers, are steerable and deflectable, and have 2D, color Doppler, and spectral Doppler capabilities. The ImageMate system has two directions of steering (anterior and posterior) whereas the AcuNav system has four (anterior/posterior and right/left). All three systems utilize a single-use ICE imaging catheter and require 8–11 French venous access. Additional detailed information about available systems can be found in Chapter 3.

Benefits of ICE

The image quality of ICE is comparable to TEE but avoids the need for esophageal intubation, as well as for additional echocardiography support. Interventionalists and electrophysiologists can be trained to become competent solo operators. ICE guidance of radiofrequency ablation for atrial fibrillation and transcatheter atrial septal closure procedures has become the standard of care for these procedures in many centers.^{1,2,26,27,28,29,30,31,32,33,34,35,36,37,38}

Although both TEE and ICE can be used to guide interventional procedures, prolonged esophageal intubation in a supine patient usually requires general anesthesia. By avoiding endotracheal intubation and general anesthesia, ICE shortens the time required to complete the procedure.^{26, 27, 28,39,40} Compared to TEE guidance, ICE improves patient comfort, shortens procedural and fluoroscopic times, and is comparable in cost to TEE-guided interventions.^{26, 27, 28,37, 38, 39, 40} when the cost of anesthesia and TEE are included. ICE can also guide transseptal punctures, placement of left atrial ap...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• List of Contributors
• Preface
• Acknowledgements
• Dedication
• 1. Why intracardiac echocardiography?
• 2. Physics and instrumentation of ultrasound
• 3. Intracardiac echocardiography: currently available ICE systems
• 4. Radial intracardiac echocardiography: intracardiac anatomy, image acquisition, and role in interventional procedural guidance
• 5. Intracardiac echocardiography: principles of image acquisition and intracardiac anatomy with the phased array transducers
• 6. ICE-guided percutaneous non-coronary interventional procedures
• 7. Intracardiac echocardiography for percutaneous atrial septal defect closure
• 8. Use of intracardiac echocardiography during ablation for atrial fibrillation