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Intracardiac Echocardiography Evolving Use in Interventional Cardiology Jon C. George, MD, Vincent Varghese, DO, Allen Mogtader, MD

Article includes CME test

Received February 4, 2013, from the Division of Cardiovascular Medicine, Deborah Heart and Lung Center, Browns Mills, New Jersey USA. Revision requested February 25, 2013. Revised manuscript accepted for publication June 30, 2013. Address correspondence to Jon C. George, MD, Cardiac Catheterization Laboratory, Deborah Heart and Lung Center, 200 Trenton Rd, Browns Mills, NJ 08015 USA. E-mail: [email protected] Abbreviations

ASD, atrial septal defect; CS, coronary sinus; IAS, interatrial septum; ICE, intracardiac echocardiography; IVS, interventricular septum; LA, left atrium; LAA, left atrial appendage; MV, mitral valve; PFO, patent foramen ovale; PS, pericardial space; PV, pulmonic valve; RA, right atrium; RV, right ventricle; RVOT, right ventricular outflow tract; TAVI, transcatheter aortic valve implantation; TEE, transesophageal echocardiography; 3D, 3-dimensional; TV, tricuspid valve; VSD, ventricular septal defect doi:10.7863/ultra.33.3.387

Intracardiac echocardiography (ICE) uses a catheter-based steerable ultrasound probe that is passed into the right heart chambers to image intracardiac structures. The transducer can be variably positioned for optimal imaging: in the inferior vena cava to visualize the abdominal aorta; in the right atrium for the interatrial septum, aortic, mitral, and tricuspid valves, and pulmonary veins; or in the right ventricle for the left ventricular function, outflow tract, or pulmonary artery. Intracardiac echocardiography is primarily used for imaging during an invasive cardiac procedure using conscious sedation, when transthoracic image quality would likely be inadequate, and transesophageal imaging would require general anesthesia. Intracardiac echocardiography is generally well tolerated and provides adequate images and sufficient information for the procedure performed. In the cardiac catheterization laboratory, ICE is routinely used for patent foramen ovale, atrial septal defect, and ventricular septal defect closures, allowing adequate percutaneous placement of septal occluders. It is now being considered in the current era of transcatheter aortic valve implantation necessitating improved imaging approaches for accurate placement. It is also routinely used for trans-septal punctures during mitral valvuloplasty and, more recently, with the advent of left atrial appendage closure devices. This article provides a comprehensive review of the current technology for ICE and its growing applications in the realm of interventional cardiology. Key Words—interventional cardiology; intracardiac echocardiography; vascular ultrasound


ltrasound imaging with intracardiac echocardiography (ICE), during select interventional cardiovascular procedures (Table 1), has gained widespread acceptance and recognition. Most often used for atrial septal defect (ASD) or patent foramen ovale (PFO) closure, it is also used to guide trans-septal puncture, mitral or pulmonic balloon valvuloplasty, ventricular septal defect (VSD) closure, and, more recently, transcatheter aortic valve implantation (TAVI). Although transesophageal echocardiography (TEE) may provide adequate ultrasound imaging, the necessities of general anesthesia and tracheal intubation for airway protection as well as the risk of esophageal perforation limit its practical utility.1 In addition, ICE may provide clearer imaging, shorter procedure times, and a reduced radiation dose to the patient while maintaining a comparable financial cost as TEE.2–4 With continued advancements in image quality, diminishing probe sizes, and the development of 3-dimensional (3D) echocardiography, ICE will continue to complement the evolution of interventional cardiology.

©2014 by the American Institute of Ultrasound in Medicine | J Ultrasound Med 2014; 33:387–395 | 0278-4297 | www.aium.org

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History The introduction of ICE in clinical medicine began in the 1960s. Early models were limited by the mechanical and rotational imaging of a single piezoelectric crystal on the tip of a 6F or 10F catheter.5 The availability of only higher frequencies additionally limited imaging depth. By 1969, Bom et al6 had developed a 32-element phased array coil in Rotterdam. During the 1980s, the advent of intracoronary ultrasound led to its first clinical use in cardiology.7 The subsequent development of lower-frequency transducers, which allowed for greater imaging depth with visualization of cardiac chambers and soft tissue structures, led to some of the earliest investigations in intracardiac anatomy during the 1990s.8

Technology There are two types of ICE catheters currently available for use during interventional procedures. The first is a mechanical tipped ultrasound transducer, such as the Ultra ICE catheter (Boston Scientific, Natick, MA), which is a 9F 9-MHz catheter capable of producing a 360° radial image. The advantages of this catheter are a large field of view with 3D reconstruction capabilities; however, a guide wire is required, Doppler interrogation is not available, and imaging depth is limited to 5 cm.

Table 1. Intracardiac Echocardiographic Catheter Positioning for Diagnostic and Therapeutic Interventional Procedures Interventional Procedure ASD and PFO closure VSD closure Trans-septal puncture LAA occlusion AV interventions MV interventions

PV interventions TV interventions Pericardial procedures

Catheter Position RA (home view) RA (posterior rightward) RA (superior) RA RV (anterior) RA (posterior) RA (clockwise) RA (clockwise) RA (posterior) RV (anterior) CS RA (home view) RV RA (home view) RV (posterior) PS

AV indicates aortic valve; and LV, left ventricle.



The second type is a phased array transducer composed of multiple crystals, electronically directed to produce a 90° imaging sector, similar to transthoracic echocardiography or TEE.7 These transducers, such as the AcuNav catheter (Siemens Medical Solutions, Mountain View, CA), are steerable 8F or 10F catheters with Doppler capabilities. Frequencies range from 5.5 to 10 MHz, allowing an imaging depth of 12 cm with the 10F catheter and 16 cm with the 8F system. Furthermore, the device is positioned under fluoroscopic guidance without necessitating guide wire support.9 Due to the Doppler capabilities and superior imaging range, this system is the one that is primarily used in the clinical application of ICE.

Safety and Feasibility In two series conducted by Earing et al10 and Hijazi et al,11 there were no reported vascular complications in more than 100 ICE procedures. The most common complication was atrial tachycardia, in up to 4% of patients, during ICE catheter manipulation within the right atrium (RA).

Clinical Application Atrial Septal Defect and Patent Foramen Ovale Closure The use of echocardiography has become an integral component in the percutaneous treatment of structural heart disease. Historically, TEE has provided excellent imaging and assessment of the interatrial septum (IAS) to guide device closure; however, the necessity of general anesthesia and a separate echocardiographic operator have made it less favorable than ICE. Moreover, a series by Mullen et al12 found similar efficacy between TEE and ICE in assessing percutaneous closure of ASDs. In addition, a study by Alboliras and Hijazi13 demonstrated a minimal cost difference between ICE and TEE. In percutaneous ASD or PFO closure, the ICE catheter is advanced into the RA with the imaging plane directed toward the tricuspid valve (TV) to display the “home” view (Figure 1). In this view, the TV, right ventricular (RV) inflow and outflow, and long axis view of the pulmonic valve (PV) are visible. An accurate assessment of the TV and any substantial regurgitation are important in determining the suitability of percutaneous closure.14 The presence of severe tricuspid regurgitation may necessitate open surgical closure of the ASD/PFO with repair of the TV. Slight posterior rotation and rightward movement of the probe brings the IAS into view to assess the ASD or PFO (Figure 2). The coronary sinus (CS) and pulmonary veins can also be identified in this view. Advancing the

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Figure 1. Right ventricular inflow view displaying the RA as well as TV and PV.

Figure 3. Caval view of the interatrial septum with the RA, LA, and superior vena cava (SVC).

probe toward the superior vena cava, while facing the septum, visualizes the IAS in a superoinferior plane (Figure 3). By rotating the entire handle clockwise, a short-axis view of the IAS is seen (Figure 4). Specific maneuvers identifying the location and size of the defect, adequacy of surrounding rims, normal pulmonary vein insertion, and confirmation of interatrial shunting by Doppler imaging and agitated saline assist in the appropriate selection of patients and positioning of percutaneous device closure (Figure 5).

imembranous portion of the interventricular septum (IVS). Long-axis, short-axis, and 4-chamber views can be obtained by manipulation of the catheter within the RA (Figure 6). If the patient has an ASD or PFO, the ICE catheter can be advanced through the defect into the left atrium (LA), and VSD interrogation can be performed with images similar to those of TEE.15 Alternatively, the ICE catheter can be flexed and advanced across the TV into the RV and rotated anteriorly to image the IVS and VSD for measurements (Figure 7) and device deployment (Figure 8). One smaller study of 12 patients, comparing TEE and ICE, found that ICE provided similar anatomic views and measurements to safely guide membranous VSD closure.16

Ventricular Septal Defect Closure With the advent of percutaneous VSD closure, ICE imaging, similar to that in ASD closure, provides an ultrasound image to guide proper device deployment. Muscular VSDs can be difficult to delineate, and TEE may need to be used for complete assessment; however, membranous VSDs are readily visible with the ICE catheter positioned in the RA. The ICE catheter, positioned in the mid RA in a neutral position facing the TV, shows the RV inflow and the perFigure 2. Interatrial septal view showing the RA, LA, and a large secundum ASD.

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Trans-Septal Puncture Trans-septal puncture guided by ICE is used to access the LA and mitral valve (MV) for balloon valvuloplasty in the treatment of mitral stenosis, for radiofrequency ablation of left-sided foci of arrhythmias, and, more recently, Figure 4. Short-axis view of the interatrial septum with the RA, LA, and aortic valve (AO).


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for left atrial appendage (LAA) exclusion. Echocardiographic visualization of the atrial septum, particularly the fossa ovalis, during puncture lowers the risk of damaging surrounding structures such as the atrioventricular valves and the aorta.17 Trans-septal puncture is best performed with the ICE catheter in the mid RA and flexed posteriorly to show tenting of the IAS with advancement of the puncture needle (Figure 9). Transthoracic echocardiography or TEE may also be used for nonfluoroscopic imaging of the septum in trans-septal puncture; however, these techniques tend to be more cumbersome than ICE.

Left Atrial Appendage Occlusion The LAA can be readily imaged by rotating the ICE catheter clockwise from the mid RA at the level of the TV past the aorta until the LAA appears at the level of the mitral annulus (Figure 10). Left atrial appendage occlusion device implantation is on the horizon of reaching mainstream interventional cardiology practice. Used for the prevention of thrombus formation within the LAA, and subsequent stroke, in patients with atrial fibrillation, ICE will allow accurate assessment of the size and shape of the LAA as well as guide device placement. Complications of






Figure 5. Deployment of an ASD occluder using ICE imaging showing the baseline ASD (A), deployment of the left disk within the LA (B), apposition of the left disk against the LA septum (C), deployment of the right disk against the RA septum (D), and final result after deployment completion (E).


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LAA occlusion such as MV or pulmonic vein obstruction, pericardial effusion, and a suboptimal device position will also be expeditiously recognized using ICE guidance. Aortic Valvuloplasty and Valve Implantation The development of TAVI has revolutionized the world of valvular heart disease. As TAVI technology continues to expand, the use of echocardiographic imaging for implantation will remain essential for accurate assessment of preprocedural anatomy and postprocedural valve function and potential complications. Transesophageal echocardiography remains the echocardiographic modality of choice currently; however, ICE may offer advantages of avoiding general anesthesia and a separate echocardiographer while providing sufficient imaging data for evaluation of the valve (Figure 11) and performance of valvuloplasty and valve implantation as these procedures become more wide-

spread. A recent study randomizing 50 TAVI procedures to ICE or TEE for imaging guidance found ICE to be a suitable alternative, with adequate imaging and hemodynamics assessment along with continuous visualization without the need for probe repositioning during the procedure.18

Figure 8. Deployment steps of a VSD occluder using ICE imaging showing the baseline VSD (A), wire across the VSD (B), and deployment of the VSD occluder (C). A

Figure 6. Four-chamber view with Doppler color flow obtained by manipulation of the ICE catheter within the right atrium showing an intact IVS.


Figure 7. Right ventricular view of the IVS to allow measurements of the muscular VSD dimensions. C

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evaluating the suitability and efficacy of repair. Furthermore, intra-CS ICE has been used to delineate the mitral isthmus, atrioventricular groove vessels, intra-CS muscle bundles, and MV apparatus.14 While high-quality live imaging of the MV and surrounding structures is crucial for the success of percutaneous catheter-based MV repair techniques, protocols for ICE imaging continue to be developed to guide precise deployment of sutures into the A2–P2 scallops of the MV to confirm the final result before release of the clip.20 Figure 9. Right atrial view of a sheath (arrow) across the interatrial septum after trans-septal puncture.

Pulmonic Valvuloplasty and Valve Replacement Pulmonic valvuloplasty may also be aided by echocardiographic guidance in the home view as well as within the RV to image the right ventricular outflow tract (RVOT) and PV (Figure 14). Overall, ICE enables the assessment of valvular gradients and regurgitation both before and after valvuloplasty.16

Mitral Valvuloplasty and Valve Repair The performance of mitral balloon valvuloplasty for rheumatic mitral stenosis necessitates trans-septal puncture as detailed above. Clockwise rotation of the transducer with slight posterior flexion from the home view allows visualization of the MV (Figure 12). Positioning the catheter within the RV provides an additional view of the MV (Figure 13). Mitral regurgitation is a common disease process with considerable morbidity and mortality once severe. Percutaneous mitral valvuloplasty and mitral clip edge-to-edge repair are performed under fluoroscopic and TEE guidance; however, ICE can be performed to evaluate the MV during these procedures, with the transducer positioned within the RV as well as within the RA near the atrial septum.19 In addition, in dilated sinuses, intra-CS imaging may offer a unique view of the MV apparatus. Intracardiac echocardiography from within the CS provides exceptional views of the MV and LA. With the emergence of percutaneous MV repair, CS imaging may be a valuable tool in

Pericardiocentesis and Intrapericardial Procedures Pericardiocentesis is routinely performed via fluoroscopic guidance or transthoracic echocardiographic guidance. However, in rare circumstances when the patient is intubated and cannot be positioned in the upright position for a subxyphoid approach, the pericardial space (PS) can be accessed while supine using ICE imaging to assess the effusion and monitor drainage in the setting of cardiac tamponade (Figure 15). The recent rise in epicardial ablation procedures has consequently led to the expanded use of ICE to include intrapericardial imaging. Pericardial ICE provides views of the heart from the pericardial sinuses without the limitations of traditional ICE, including catheter instability, catheter-related interference, and restricted visibility due to catheter proximity to intracardiac structures.14

Figure 10. Mid RA view of an LAA.

Figure 11. Right atrial view of the ring of a bioprosthetic aortic valve (AV) to evaluate valve function and perivalvular structures.


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This innovative ultrasound approach may provide further accurate assessment of cardiac anatomy as interventional procedures via the PS evolve, including LAA ligation and epicardial stem cell delivery. Miscellaneous Interventional Procedures In addition to the above-mentioned interventions, ICE may also assist in patent ductus arteriosus closure, perivalvular leak closure for prosthetic valves, alcohol septal ablation for hypertrophic obstructive cardiomyopathy, and endomyocardial or cardiac mass biopsies.21–23

Future Directions Intracardiac echocardiography is the most commonly used nonfluoroscopic imaging tool in the interventional laboratory.19 The advancements of ICE will include enhanced image quality and resolution, as well as smaller, more flexible, and stable transducers, which may allow for radial access intracardiac imaging. Forward-looking ICE catheters, Figure 12. Right atrial view of the struts of a bioprosthetic MV (A) and evaluation of perivalvular regurgitation (B) at the site of dehiscence from the annulus. A

Figure 13. Right ventricular view of an MV.

primarily being developed in conjunction with radiofrequency ablative devices, will provide an alternative view of cardiac anatomy.14 The use of 3D TEE in structural heart disease has provided exceptional anatomic evaluations, particularly related to TAVI and MV repair. Real-time 3D ICE is currently being developed and has the potential to enhance image acquisition and interpretation during valvular interventions. Additionally, real-time 3D ICE would allow the measurement of ventricular volumes and peak flow velocities while avoiding the use of general anesthesia and tracheal intubation for complex valvular procedures.24,25

Summary Intracardiac echocardiography has proven essential in conducting safe and efficient interventional procedures in various diagnostic and therapeutic areas (Table 1). As structural heart disease interventions continue to evolve, ICE appears poised to complement these therapeutic procedures.


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Figure 14. Right ventricular view of an RVOT and PV.


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7. 8. 9.


11. A



14. B Figure 15. Right ventricular view of pericardial effusion (PE) before (A) and after (B) pericardiocentesis.



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Intracardiac echocardiography: evolving use in interventional cardiology.

Intracardiac echocardiography (ICE) uses a catheter-based steerable ultrasound probe that is passed into the right heart chambers to image intracardia...
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