Intracardiac echocardiography

This article describes currently available intracardiac ultrasound (ICE) technology contrasting it with intravascular ultrasound (IVUS), highlighting their differences. General and specific clinical applications, limitations and future developments of ICE are addressed. ICE is possible because lower frequency transducers (in contrast to higher frequency IVUS devices) have been miniaturized and mounted onto catheters capable of percutaneous insertion into the heart. Since the recent availability of a steerable, 5.5--10MHz phased-array catheter with full Doppler capability, these lower frequency transducers are not only capable of enhanced penetration, permitting high-resolution two-dimensional (2D) imaging but can also provide haemodynamic data. ICE facilitates electrophysiologic procedures by guiding trans-septal catheterization, enabling endocardial anatomy visualization, ensuring ablation electrode/tissue contact and promptly diagnosing procedural complications. Promising non-electrophysiologic applications include guidance of percutaneous closure of septal defects, percutaneous mitral balloon valvuloplasty and complex cardiac biopsy. Current limitations include monoplanar imaging and narrow field of view. Expanded diagnostic techniques such as tissue Doppler, multiplane, three dimensional (3D) and multimodality imaging represent future refinements. ICE is now a clinical tool. With the introduction of the newest phased-array transducer, with full Doppler capability, ICE has the potential to play an important role in diagnostic and therapeutic interventional procedures. Further refinement and miniaturization hold the key to primary operator controlled, integrated ultrasound-guided interventional devices.