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Principles of Echocardiography
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Since 1976, echocardiography (echo) has been used to evaluate cardiac structure and function. Echo uses sound in the high-frequency range (2–10 MHz). Frequency ranges between 2 and 5 MHz are typically used for imaging adults, while frequencies of 7.5 to 10 MHz are used for children and specialized adult applications. The transducer contains a piezoelectric crystal that converts electrical to sound energy, producing sound waves that are transmitted in the form of a beam. A complete transthoracic echocardiogram (TTE) consists of a group of interrelated applications including two-dimensional (2D) anatomic imaging, M-mode, and three Doppler techniques: pulsed-wave (PW), continuous-wave (CW), and color-flow (CF) imaging.1–7 In addition, the quantification of cardiac chamber dimensions, areas, and volumes is an important aspect of a complete examination. Using a combination of these ultrasound techniques, one can assess the anatomy and function of the cardiac valves, myocardium, and pericardium.
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Two-Dimensional Echocardiography
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Standard views are obtained along three orthogonal planes of the left ventricle (LV): long-axis, short-axis, and the four-chamber plane (Fig. 56-1A–C). The long axis is parallel to the long axis of the LV. The short axis cuts the LV cross-sectionally, similar to slices of bread in a loaf, and is orthogonal to the long axis. Four standard transducer locations are used to obtain complete visualization of the entire heart: parasternal, apical, subcostal, and suprasternal.
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M-Mode Echocardiography
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M-mode is a one-dimensional “ice pick” view of the heart (Fig. 56-1D) and is often used for measuring LV systolic and diastolic chamber dimensions and wall thickness.
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Doppler Echocardiography
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The Doppler effect is the phenomenon whereby the frequency of sound waves increases or decreases as the sound source moves toward or away from the observer. The resultant Doppler frequency shift can be detected and translated into blood-flow velocity. ...