The term echocardiography refers to the evaluation of cardiac structure and function with images and recordings produced by ultrasound. In the past 30 years, it has become a fundamental component of the cardiac evaluation. Currently, echocardiography (echo) provides essential (and sometimes unexpected) clinical information and is the second most frequently performed diagnostic procedure.
A one-dimensional (1D) method performed from the precordial area to assess cardiac anatomy has evolved into a two-dimensional (2D) modality performed from either the thorax (TTE) or from within the esophagus (TEE), capable of also delineating flow and deriving hemodynamic data. Newly evolving technical developments have extended the capacity of ultrasound to routine three-dimensional (3D) visualization and the assessment, in conjunction with contrast agents, of myocardial perfusion.
The development of echocardiography is usually credited to Elder and Hertz in 1954. For nearly two additional decades, clinical echocardiography consisted primarily of 1D time-motion (M-mode) recordings, as popularized by Feigenbaum. In the mid-1970s, Bom and colleagues developed a multielement linear-array scanner that could produce anatomically correct images of the beating heart. 2D images of superior quality were soon achieved by mechanical sector scanners and ultimately by phased-array instruments developed by VonRamm and Thurstone9 as the present-day standard. Recently, 3D instruments capable of real-time volumetric imaging have been developed.10 Miniaturization of ultrasound transducers has also led to handheld echographs that can be carried in a lab coat and incorporation into gastroscopes and cardiac catheters to achieve transesophageal and intravascular.
Although efforts to use the Doppler principle to measure flow velocity by ultrasound were begun in the early 1970s by Baker,13 clinical application of this technique did not thrive until the work of Hatle in the early 1980s.14 Pulsed and continuous-wave Doppler recordings soon were expanded to full 2D color-flow imaging. Most recently, Doppler velocity recordings have been obtained from myocardium itself, enabling measurement of tissue velocities and the derivation of values for regional strain.