![]() ![]() When these lines of ultrasound images were plotted concerning time, an M-mode (motion mode) was produced. Initially, echocardiographic images were obtained by sending ultrasound waves along a single line followed by the display of amplitude of the reflected signal as well as the depth of that signal on an oscilloscope, which was called A-mode echocardiography. An electrocardiogram is used as a timing marker for digital recording gating of echocardiographic images. The modified electrocardiogram (ECG) leads are placed, which allow identification of arrhythmias and timing of cardiac events during the echocardiographic examination. The subcostal and suprasternal views require the patient to be in the supine position. This position brings the heart into close contact with the chest wall. Patient Position and Electrocardiography Lead Placementįor the parasternal and apical tomographic views, the patient is required to lie in the left lateral decubitus position, with the left arm extended behind the head. ![]() The two-dimensional image is formed by displaying the intensities of the echos and the distances calculated. Distance from the probe to the tissue is calculated using the speed of sound in the tissue and the time of each echo's return. The tissues and the boundaries between them reflect the waves back to the probe. ![]() The ultrasound probe transmits sound waves to the body part which is being imaged. On receiving the reflected ultrasound waves, the transducer generates an electrical signal analyzed by the echo machine. On applying varying voltages, it vibrates and transmits ultrasound. Each echocardiographic machine probe has this piezoelectric crystal transducer. This phenomenon of inter-conversion of electrical and mechanical oscillations is called the piezoelectric effect. In contrast, the reflected mechanical waves are converted back to electrical signals. Ultrasound waves are produced due to the transformation of electrical oscillations into mechanical (sound) waves by the crystals in an echocardiographic probe. The normal velocity of sound in air is 330 m/s, while in the heart tissue, the velocity is around 1540 m/s. The velocity of these waves depends on the nature of the material in which the sound travels. (Figure 1)Įchocardiographic probes utilize ultrasound waves (sound waves) of frequencies ranging from 1.5 to 7.5 MHz. On echocardiographic parasternal long-axis views, the right ventricular free wall is the anterior-most structure while the left ventricular posterior (inferolateral) wall is the posterior-most structure. Īt other times, diseases of the lung or pleura or other mediastinal structures can displace the heart, making image acquisition and interpretation a challenging proposition. There are variations in this cardiac position related to the patient's body habitus, and minor changes may occur with respiration. The heart is normally positioned within the middle mediastinum with one-third of its mass located to the right side of the midline, and its own long axis is directed from the right shoulder (base of the heart) towards the left hypochondrium (apex of the heart). ![]() This chapter aims to review the basics of ultrasound physiology, important terms used in echocardiography, different echocardiographic techniques, and basic echocardiographic views. Even in the contemporary era of newer imaging modalities, an echocardiogram is recommended as the first choice for structural and functional assessment of the heart. In other circumstances, new technologies have been incorporated to enhance existing capabilities. In some aspects, new technologies have completely replaced old methods. With the advent of echocardiographic contrast media and transesophageal probes, the sensitivity of echocardiographic examination has improved significantly, and it has become an important part of cardiac surgical procedures involving valvular reconstruction. Although echocardiography started with B-mode, with the discovery of new technologies, including Doppler and 3-dimensional imaging, the echocardiographic examination has progressively become longer and more comprehensive. Since then, echocardiography has expanded tremendously and exponentially over the decades and has become an integral part of cardiac evaluation. The assessment of the mitral valve with the help of M-mode was the first clinical application of an echocardiogram. They used an industrial ultrasonic flaw detector and obtained time-varying echoes transcutaneously from the heart. Hertz and Edler reported the first use of ultrasound in the cardiac evaluation and continuous monitoring of heart movements in 1954. The basic concept of echocardiography was first demonstrated by Lazzaro Spallanzani in the 18 century when he described the reflected echoes of inaudible sound. ![]()
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