Feasibility study: Transesophageal echocardiography with a 10F (3.2- mm), multifrequency (5.5- to 10-Mhz) ultrasound catheter in a small rabbit model

Transesophageal echocardiography (TEE) is useful in children with congenital heart defects. However, because of available probe size (≥7 mm diameter), its use is limited to patients weighing more than 3 kg. The aim of this study was to determine the feasibility of TEE in a small animal model by using a 10F (3.2-mm) intravascular ultrasound tipped catheter with a monoplane (longitudinal) 5.5- to 10-MHz phased vector array transducer. Ten New Zealand White rabbits (400 to 3400 g; mean 1580 g) underwent TEE. With animals under general sedation, the probe was blindly introduced into the esophagus. All intracardiac and extracardiac structures were examined, and the images were stored and independently reviewed. All pertinent intracardiac and extracardiac structures were identified except in the 3 smallest rabbits (400 to 600 g). Doppler hemodynamics and color Doppler were possible in each animal. Frequency agility (5.5 to 10 MHz) facilitated optimization of image resolution and penetration. Certain transgastric, 4-chamber, and short-axis views were limited because of the monoplane array. No overt adverse effects were associated with the procedure. Diagnostic TEE can be performed in a small animal model with a 10F, 5.5- to 10-MHz phased vector array ultrasound catheter. Our study suggests that this system has potential in performing diagnostic TEE safely in small, even premature, neonates.