In some people the probe is almost flat against the

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left chest cavity where the heart lies. In some people, the probe is almost flat against the abdominal wall. Because the beam is transmitted over a 64 Diagnostic ultrasound Cardiac ultrasound
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fairly long distance (usually 7–10 cm), it is best to start with the screen at maximum depth so the longest distance is visualized on the screen. Once the heart is identified, the depth can be adjusted to enlarge the image as appropriate. The liver and then right ventricle are closest to the probe and so will be most superior on the ultrasound screen. The bright white pericardium is seen in Figure 3.5 ; it is flush up against the gray myocardium, indicating no effusion is present. Often stomach or intestinal gas interferes with the subxiphoid view. When this occurs the probe should be moved toward the patient’s right side to better use the liver as an acoustic window ( Figure 3.6 ) (A) (B) Figure 3.3 Probe positioning for subxiphoid view. ( A ) Begin with the probe several centimeters inferior to the xiphoid process and slide the probe cephalad (in direction of arrow) until ( B ) it “nestles” in the subxiphoid area. ( C ) Note the angle the transducer must make in order to visualize the heart. Probe marker (green dot) faces patient’s right side. Diagnostic ultrasound 65 Cardiac ultrasound
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The subxiphoid four-chamber view gives a good view of the right ventricle and is often used to look for a pericardial effusion. It is also the standard view for cardiac evaluation during the FAST exam. Figure 3.4 Orientation of probe and image for the subxiphoid four-chamber view (probe marker noted with a green dot). Right Ventricle Left Ventricle Right Atrium Left Atrium Mitral Valve Tricuspid Valve Figure 3.5 Cartoon of subxiphoid view with corresponding anatomy as visualized by ultrasound. Courtesy of Dr. Manuel Colon, Hospital of the University of Puerto Rico, Carolina, PR. 66 Diagnostic ultrasound Cardiac ultrasound
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Left parasternal long-axis view Assuming the long axis of the heart to be from the patient’s right shoulder to the left hip, the transducer probe should be placed in the third or fourth intercostal space, immediately left of the sternum ( Figure 3.7 ). The probe indica- tor should be pointing toward the 5 o’clock position or toward the patient’s left hip ( Figure 3.8 ). In this position, the depth on the machine does not need to be as great because the structures of interest should be fairly close to the probe. The angle of the probe should be adjusted to place the beam along the electrical vector of the heart. There are three points which define the plane of the parasternal long-axis view: ± Mitral valve ± Aortic valve ± Cardiac apex When these three structures are visualized simultaneously, the probe is oriented correctly along the long axis of the heart. This is not only Figure 3.6 Moving the probe toward the patient’s right side avoids bowel gas and optimizes the liver window in the subxiphoid view. Note significant interference from stomach gas obscuring view. This is decreased incrementally (clockwise from top left) as the probe is moved toward the patient’s right side, maximizing use of the liver as a window.
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