Development of Transesophageal Echocardiography

Abstract

Technology using reflected sound waves to localize objects was initially developed for naval sonar but expanded in many directions. The use of ultrasound for imaging dynamic cardiac structures was first introduced in 1954 by Edler and Hertz [1] and has since revolutionized diagnostic approaches to cardiac disease. Ultrasound waves reflected from cardiac surfaces can be presented as dots or moving lines (M-mode echocardiography), but a more understandable representation of the heart is provided when the reflected ultrasound waves are oriented in two dimensions to produce an image resembling a cross section of the heart (2D echocardiography). Transmission of ultrasound into living tissue has proved to be safe, and comfortable for patients; thus since 1954 many refinements have taken place to explore its full potential in clinical and research use. A variety of hand-held transducers capable of emitting and receiving ultrasound have been used by cardiologists. The standard technique requires that the transducer is placed on the skin surface overlying the heart. Since ultrasound frequencies are not transmitted well through air, contact between the skin and the transducer is maintained by the use of a coupling gel applied liberally to the skin. The heart lies at a variable depth within the thorax and thus cardiac imaging is often facilitated by positioning the patient on his left side so that the heart falls against the left anterior chest wall. With all the various improvements in equipment, successful cardiac imaging still requires first of all that the heart lie within the field of view of the ultrasound transducer, and it is essentially this particular aspect of imaging that led to the development of esophageal transducers.