Transthoracic echocardiography (TTE) is the primary noninvasive imaging modality for quantitative and qualitative evaluation of cardiac anatomy and function [1,2]. Two-dimensional (2D) echocardiography provides tomographic or "thin slice" imaging. Comprehensive echocardiographic examination typically involves imaging the heart from multiple "viewing" orientations. A three-dimensional (3D) appreciation of cardiac anatomy is needed to integrate 2D (and M-mode) echocardiographic information.
Echocardiographs equipped with 3D capability have been developed to overcome the disadvantages of tomography [3-5]. These devices generally acquire a volumetric data set which can then be displayed in custom orientations. The specific clinical advantages of 3D echocardiography are being defined and gaining increasing clinical importance. (See "Three-dimensional echocardiography".)
The nomenclature, standard protocol, and normal views associated with TTE are reviewed here. The instrumentation and physics associated with echocardiography, along with discussions of various echocardiographic techniques, are presented separately. (See "Echocardiography essentials: Physics and instrumentation" and "Principles of Doppler echocardiography" and "Tissue Doppler echocardiography".)
Each tomographic view is defined by the transducer position (parasternal, apical, subcostal, suprasternal) and view (long axis, short axis, four-chamber, five-chamber). Transducer position is altered by placing the transducer at various locations on the thorax, while the view is manipulated by a combination of angulation and rotation. Due to limitations imposed by the thoracic skeleton and lungs, not all permutations of both variables result in clinically useful images.
Orientation — While acceptance is not universal, most labs follow the recommendations of the American Society of Echocardiography with respect to image display. With this convention, the transducer position is depicted at the top of the screen, with anatomy more distant from the transducer depicted at progressively lower regions of the display, the lateral/left structures to the right, and medial/right structures to the left. A linear calibration scale is provided for all two-dimensional (2D) and M-mode measurements.