Intracardiac echocardiography during transcatheter interventions for congenital heart disease

Although transesophageal echocardiography is often used for guidance during transcatheter interventions, few data exist regarding the use of the newer modality of intracardiac echocardiography. This brief report summarizes our single center experience using intracardiac echocardiographic guidance during transcatheter interventional procedures for congenital heart disease.     

Intracardiac echocardiography during catheter-based procedures: ultrasound system,examination technique,and image presentation

A detailed understanding of the anatomic structures of both atria is mandatory for successful catheter-based interventional techniques. Some of the drawbacks of transthoracic and transesophageal echocardiography can be overcome by intracardiac echocardiography (ICE). We present our ICE experience based on 70 out of 186 patients who were included in a multicenter registry of transcatheter interatrial communication closures. The ultrasound catheter was a 9-Fr, 9 MHZ monoplane probe (Ultra ICE catheter) compatible with the motor drive unit and imaging console of the Clear View Ultra. Four slice selections in the axial plane and only one in the sagittal plane were needed in order to obtain a comprehensive guide to ICE interrogation. Their intracardiac ultrasound imaging presentation is an essential and nontrivial step. The anatomic coordinate system was maintained identical to a tomographic imaging plane as follows: Left/right and anterior/posterior in the axial planes and superior/inferior and anterior/posterior in the sagittal plane. In order to identify the imaging coordinates, two specific anatomic landmarks were used. The first one was the crista terminalis (at 10 o'clock) and the second one was the right atrial auricle (at 12 o'clock). Once the ultrasound images were orientated, their interpretation and spatial reconstruction were straightforward. In conclusion, a standardized ICE examination allows for a comprehensive evaluation of the right atrial anatomy and may be helpful in guiding therapeutic catheter-based interventions. The major clinical advantages of ICE include optimal contrast between soft-tissue structures, limited fluoroscopic exposure time, and good patient acceptance, thus avoiding general anesthesia.     

Intracardiac echocardiography: current developments

Intracardiac echocardiography refers to the method of imaging cardiac structures from intracardiac locations with the use of ultrasound catheters. Advances in catheter-based interventional cardiologic procedures to treat cardiovascular lesions and the problems encountered during those procedures due to inadequate guidance provided by fluoroscopy have given the impetus to develop other guidance modalities. Experimental explorations with intracardiac ultrasound probes have indicated that detailed visualization of cardiac structures in real-time is possible by intracardiac ultrasound. Recent advances in catheter-based ultrasound technology make it feasible to safely pass small-sized catheters in humans into various intracardiac locations and acquire images of valvular structures and various chambers. Experience with 20 MHz ultrasound catheters indicates that high resolution images of normal and abnormal structures can be obtained if the catheter is manipulated close to the region of interest. The problem of the limited depth of field associated with 20 MHz catheters has led to the fabrication of catheters with lower frequency ultrasound elements. Experimental and clinical experience with 12.5 MHz ultrasound catheters points to the capability and potential of intracardiac echocardiography to not only display normal structures but also aid in the identification of valvular abnormalities, chamber dysfunction and pericardial effusions. In addition, aortic disorders such as acute dissection, coarctation and atherosclerotic disease could be delineated. Similarly, abnormalities involving the pulmonary arteries such as pulmonary embolism, organized thrombi, peripheral pulmonary arterial stenoses, and pulmonary hypertension-induced vascular changes could be recognized. Many modifications in the catheter design are being explored. With further work in the area of catheter technology and ultrasound image processing, intracardiac echocardiography is likely to become a clinical tool.     

Intracardiac echocardiography in electrophysiology

Intracardiac echocardiography (ICE) broadens the spectrum of echocardiographic techniques. Modern 10F sector echocardiographic catheters introduced into the right atrium allow high quality imaging of all cardiac structures, including pulse and continuous wave Doppler and/or color Doppler. The main indication for ICE appears to be monitoring of catheter ablation of complex arrhythmic substrates such atrial fibrillation, postincisional tachycardias and ventricular tachycardias. The other important role of ICE is the early diagnosis and prevention of complications during ablation procedures. These include those occurring during transseptal catheterization, damage to cardiac structures, left atrial thrombus formation, pulmonary venous stenosis, esophageal injury and pericardial effusion.     

The LightWire technology for catheter-based interventions.

BACKGROUND: The LightWire is a newly developed opto-acoustic coronary imaging guidewire that was designed to be used during angioplasty procedures and provide 'online' information on lumen and vessel wall dimensions. METHODS: We designed in vitro models and performed animal trials to confirm proper device sensing capabilities and performance in the coronary arteries. This report focuses on maneuverability, compatibility with other catheterization devices, and vessel measurements. RESULTS: Measurement ability was initially validated in vitro. Diameter measurements of coronary and peripheral arteries with and without stent based on ultrasound technology were then demonstrated in a pig model, whereas retaining easy navigation and maneuverability, as well as compatibility with other catheterization equipments. The LightWire device acquired proper and accurate multi-location measurements of coronary and femoral artery diameters. CONCLUSION: Using a miniaturized opto-acoustic technology can aid incoronary imaging, while maintaining standard guidewire performances. Thus, the LightWire device holds promise as a diagnostic and guidance tool during coronary and peripheral angioplasty procedures.     

Intracardiac devices for stroke prevention

Stroke is a significant cause of serious disability and death worldwide. A substantial proportion of strokes are related to an underlying cardiac embolic source, most commonly in association with atrial arrhythmias (fibrillation/flutter). Atrial fibrillation is considered a major risk factor for stroke. Although long-term prophylactic oral anticoagulation has been shown to be very effective in reducing stroke in patients with atrial fibrillation, it has a number of major limitations and is not feasible in all patients. In such cases, the use of percutaneously (transvenous) implanted left atrial appendage occlusive devices or surgical appendage obliteration is being explored. Similarly, the presence of a patent foramen ovale, especially in the presence of an atrial septal aneurysm, is now recognized as an important potential mediator of paradoxical cardiogenic embolism. Percutaneous patent foramen ovale closure is becoming increasingly established as a safe and effective means of preventing recurrent strokes in the presence of a patent foramen ovale. In this account, the authors discuss the intracardiac devices and techniques available and the relative merits of their use for stroke prevention.     

Intracardiac echocardiography: clinical utility and application

Intracardiac echocardiography (ICE) broadens the spectrum of available echocardiographic techniques and provides the operator direct visualization of cardiac structures in real time. ICE has clear advantages over fluoroscopy, transthoracic echocardiography, and transesophageal echocardiography as the imaging modality of choice in the cardiac catheterization and electrophysiological laboratories. With the development of steerable phased array catheters with low frequency and Doppler qualities, there is marked improvement in visualization of left-sided structures from the right heart. Appropriate utilization of ICE is likely to maximize safety and efficacy of complex interventional procedures and may improve patient outcomes. Future advances in ICE imaging will further improve the ease of device guidance and, in combination with new imaging modalities, could dramatically improve other applications of echocardiography which may result in improved patient outcomes. This review describes the technical evolution of ICE, the use of ICE in guiding percutaneous interventional procedures and possible future applications of ICE in the ever-growing field of interventional cardiology.     

Intracardiac echocardiography: current uses and future directions

Advances in transducer technology have enabled development of catheter-based ultrasound imaging devices that produce very high resolution images of vessels and cardiac structures. Although the majority of clinical use has been in the evaluation of the coronary and peripheral vasculature, a broad spectrum of cardiac applications continue to develop, including evaluations of the ventricles, valves, and great vessels, as well as the guidance of electrophysiological procedures. Specifically, introduction of the ultrasound catheter into the heart results in dynamic, real-time images for assessment and quantitation of ventricular systolic function, severity of valve stenosis, and extent of regurgitant orifices. The intracardiac applications have the potential to become the gold standard for quantitation of valve dynamics and a critical tool in the ICU for prolonged monitoring of cardiac physiology.     

Intracardiac echocardiography for the guidance of percutaneous procedures

Interventional cardiology has seen great advances in the past decade. A wide range of interventional procedures has been established as standard therapeutic modalities and more are yet to come. Multiple imaging modalities have been used to guide these procedures. Intracardiac echocardiography (ICE) provides an accurate imaging tool to guide the appropriate performance of many of these procedures. Early studies compared ICE as a new imaging modality to guide interventional closure of atrial communications with other more established imaging techniques, such as transesophageal echocardiography, with excellent accuracy. In this article, we discuss the value of using ICE in guiding some percutaneous interventional procedures. We also discuss the imaging protocol for using ICE to guide atrial level shunt device closure. Our experience in using ICE for guiding percutaneous valve placement is also discussed.     

Future horizons for catheter-based interventions in adult congenital and structural heart disease

In recent decades, there has been an exponential growth in both the number and range of catheter-based interventions for adult congenital and structural heart disease. In this article, we discuss the rationale for the ongoing development of minimally invasive multidisciplinary interventions; the required training elements necessary to achieve expertise in the field; the cardiac team needed to best perform these interventions; and the currently available and up and coming technologies for performing transcatheter valve therapies.     

Intracardiac echocardiography: computerized detection of left ventricular borders

A semi-automated method for two- and three-dimensional analysis of intracardiac echocardiography (ICE) images and image sequences is reported based on detection of epicardial and endocardial borders using graph searching. The border detection method was applied to 50 ICE images acquired in vivo in five dogs and to 108 images in 16 volumetric ICE image sequences from eight cadaveric pig hearts. The ICE images from the in vivo study showed good correlation between computer-detected and observer-defined left ventricular (LV) cavity areas and epicardial areas (r=0.99, y=0.98x+0.43[cm2]; r=0.99, y=0.98x+1.11[cm2]; respectively). In the cadaveric hearts, the LV volumes were determined with the volume measurement error of 7.6±7.7% and 11.3±11.2% for the aortic valve and mitral valve image sequences, respectively. Our method facilitates an accurate and computationally efficient approach for the quantitative assessment of ICE image data in 2D and 3D.     

Intracardiac echocardiography guidance for alcohol septal ablation in hypertrophic obstructive cardiomyopathy

Intracardiac echocardiography (ICE) was used in a 17-year-old female with refractory symptoms and hypertrophic obstructive cardiomyopathy (HOCM) to guide alcohol septal ablation. During the procedure ICE readily identified the hypertrophied interventricular septum, the dynamic intraventricular gradient, the systolic anterior motion of the mitral valve and the associated mitral regurgitation. Notably, a perfect match was demonstrated between transthoracic echocardiography and ICE findings regarding contrast location. Potential complications related to this technique and alternative therapeutic strategies are discussed. This report highlights the potential use of ICE to guide procedures of alcohol septal ablation in patients with HOCM.     

Intracardiac echocardiography in electrophysiology: a review of current applications in practice

Intracardiac echocardiography (ICE) has emerged as a widespread useful tool in the everyday practice of interventional electrophysiology. Advances in catheter-based ultrasound transducers and imaging technology have made this modality integral to guiding evaluation of anatomy and ablation therapy. Evolution of ablative procedures of the left heart for tachyarrhythmia has highlighted the importance of direct visualization of anatomic landmarks to guide transseptal catheterization and immediately identify complications. The ability to position mapping and ablation catheters according to anatomic landmarks (Fig. 1) has greatly enhanced the safety and efficacy of catheter ablation procedures. ICE has supplanted fluoroscopy as the gold standard for precise imaging of endocardial structures during complex procedures.