Clinical applications of intracardiac echocardiography in interventional procedures

Abstract

A ccurate knowledge of the anatomy of intracardiac structures is essential for the efficiency and safety of performing interventional procedures. Although fluoroscopy is an important aid while advancing catheters in the heart, it is not sufficient to supply accurate anatomical information on the position of veins, ridges, and septa in the heart. Furthermore radiation exposure forms a risk to both the patient and the operator.Intracardiac echocardiography (ICE) is a promising technique for imaging of intracardiac structures, and may serve as an alternative for the transoesophageal approach, 1 which is semiinvasive and requires anaesthesiology. The introduction of ICE catheters with low frequencies allows accurate visualisation of intracardiac anatomical structures with an ultrasound catheter placed exclusively in the right side of the heart. This report focuses on the use of ICE in guiding percutaneous interventional procedures. BASICS OF INTRACARDIAC ECHOCARDIOGRAPHY cHistory of two dimensional intracardiac ultrasound systems The first application of ICE was done using mechanical ultrasound systems, which were introduced in the 1980s. These systems provided high resolution imaging, but because of the high frequency of the transducers (20-40 MHz), tissue penetration was only limited and anatomic intracardiac overviews could not be obtained. The subsequent development of lower frequency transducers allowed imaging of intracardiac structures, but these systems were still limited by the low steerability and over-the-wire design of the catheters. 2 The clinical use was improved by the development of flexible lower frequency transducers (9 MHz), but depth control of these catheters still was not sufficient to allow visualisation of the whole heart from the right side of the heart. In the 1990s, systems modified after transoesophageal echocardiographic probes were introduced. In these systems depth was improved by the use of lower frequencies (5 MHz). However, the large size of these transducers limited the clinical use. In recent years the development of steerable phased array ultrasound catheter systems with low frequency and Doppler qualities has expanded the clinical use of ICE.

Multi-modality imaging to assess left atrial size, anatomy and function

“…Therefore, no standardised measurements of LA size or volume are available. During these interventional procedures, ICE can accurately visualise LA anatomy and related structures 29. Furthermore, it allows visualisation of intracardiac devices and catheters, and is helpful in monitoring potential complications during catheter ablation procedures 30.…”

“…The Doppler capacities and the ability to monitor the catheter position in relation to the pulmonary veins are great advantages of this technique 29. In addition, ICE is helpful in assessment of the transmural extent of the ablation lesions50 and ICE has been used to titrate ablation energy, thereby increasing the safety of the ablation procedure 30.…”

History of echocardiography and its future applications in medicine

“…High-frequency (9 MHz) ultrasound transducer-tipped catheters recently have been used for guiding percutaneous interventional procedures, such as transseptal puncture, placement of closure devices, and catheter-based electrophysiological interventions (44). With emergence of newer techniques for percutaneous valve repair, the application of this technology is likely to greatly increase.…”

Ultrasound compatible RF ablation electrode design for catheter based guidance of RF ablation — In vivo results with thermal strain imaging

“…Since intracardiac echo (ICE) imaging catheters for the guidance of interventional electrophysiology (EP) therapeutic procedures offer real time, direct observations and improved procedural guidance over that of fluoroscopy alone [1], their use is constantly increasing. Currently atrial fibrillation, the most common cardiac dysrhythmia, affects more than 2.2 million in the U.S. alone with at least 60,000 new cases each year [2].…”