Real‐Time Intracardiac Two‐Dimensional Echocardiography: An Experimental Study of In Vivo Feasibility, Imaging Planes, and Echocardiographic Anatomy

Abstract

The traditional transthoracic and transesophageal echocardiographic examination have proven to be useful imaging tools for studying cardiac morphology, pathology, and function. Recently, catheter-based ultrasound transducers have been available for intravascular ultrasonic imaging. We supposed that echocardiographic examination performed from within the heart itself can provide useful information about cardiac structure and function, especially in settings where transthoracic or transesophageal echocardiography may be technically difficult to perform or poorly tolerated by the patient. To explore this concept, we performed intracardiac echocardiography in vivo in 22 dogs using both 5-MHz and 20-MHz transducers. High-quality images were obtained in all animals. Using the higher frequency transducer, detailed images with only a limited depth of field were obtained. With the 5-MHz transducer, a comprehensive cardiac examination was feasible from within the right atrium and inferior vena cava. We were able to visualize the great vessels, all cardiac valves, and cardiac chambers in a multitude of imaging planes. Alterations in ventricular function were instantly recognized. Color Doppler capabilities allowed visualization of flow abnormalities as well. We conclude that intracardiac echocardiography is feasible and could be potentially useful in certain clinical situations. With further research and development, this technique may have an important clinical impact in cardiac therapy and diagnosis.

Invasive echocardiography: The use of catheter imaging by the interventional cardiologist

“…The initial clinical experience with ICE was reported in the early 1990s [33][34][35][36][37] for guidance during Brockenbrough transseptal puncture [38], for the assessment of left ventricular mass [39], and for the assessment of atrial septal defect anatomy [40,41]. More recently reported applications include guidance during balloon atrial septostomy in end-stage pulmonary hypertension [42] and transcatheter device closure of atrial septal communications [43].…”

Experimental Studies With a 9F Forward-Looking Intracardiac Imaging and Ablation Catheter

“…Catheter ablation is now performed for virtually every type of arrhythmia including Wolff-Parkinson-White syndrome (3,4), concealed accessory pathways (3,4), atrioventricular nodal reentrant tachycardia (7), atrial flutter (8), atrial fibrillation (9), incisional atrial reentrant tachycardia (10), and ventricular tachycardia (7). Catheter ablation is also performed in all chambers of the heart, and in patients with diverse structural cardiac abnormalities (11). …”

“…A common energy source for ablation is radiofrequency (RF) current. A special catheter, equipped with one or more RF electrodes and a temperature sensor at the tip, is placed in the area of interest and connected to an RF generator producing a signal at about 500 kHz (11). This energy applied to tip electrodes in contact with cardiac tissue can create heating of the distal electrode tip to 50–70°C, which is transmitted to the adjacent cardiac tissue resulting in irreversible cell death and heat necrosis of the underlying tissue (12).…”

Development of an Electrophysiology (EP)-Enabled Intracardiac Ultrasound Catheter Integrated With NavX 3-Dimensional Electrofield Mapping for Guiding Cardiac EP Interventions

“…13,14 Intracardiac echocardiography (ICE) has allowed imaging from the right side of the heart for imaging both right-and left-sided cardiac chambers and structures. [15][16][17][18][19][20][21][22][23] Although the earlier devices were lower-frequency versions of intracoronary intravascular ultrasound devices (often mechanically driven), later devices also provided color and spectral Doppler imaging.…”