Transesophageal echocardiography: Anatomic considerations

Published on 07/02/2015 by admin

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Last modified 07/02/2015

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Transesophageal echocardiography: Anatomic considerations

Kent H. Rehfeldt, MD, FASE and Martin D. Abel, MD

Echocardiography typically uses ultrasound frequencies between 2 million and 10 million hertz (or 2-10 MHz), which is well above the audible range of humans (20-20,000 Hz). Sound waves are absorbed, reflected, and scattered to varying degrees by passage through human tissue. Reflected echoes are produced at boundaries between two inhomogeneous media (e.g., blood–soft tissue interface). More homogeneous tissues result in greater ultrasound scattering and less reflection.

Most transesophageal echocardiography (TEE) probes in use today have multiplane imaging capability. That is, the imaging plane of the transducer at the distal tip of the probe can be electronically rotated between 0 degrees (horizontal or transverse plane) and 180 degrees. The image obtained at 180 degrees represents a right-left mirror image of the view obtained at 0 degrees. Older probes and some pediatric probes are equipped with two transducers at their distal ends, one that generates transverse (or 0 degrees) imaging planes, with a second transducer producing longitudinal (or 90 degrees) imaging planes. The operator selects the desired imaging plane of these biplane probes by means of a button on the ultrasound machine itself.

Transesophageal echocardiography safety

Numerous complications have been attributed to TEE use, including vocal cord paresis, dysphagia or odynophagia, inadvertent manipulation of the tracheal tube, bronchospasm, arrhythmias, and vascular compression during flexion of the probe tip, particularly in infants. Minor trauma to the hypopharynx is not an uncommon finding following probe insertion. In one study, fiberoptic examination revealed hypopharyngeal hematoma or laceration in 24% of adult patients after typical blind insertion of the TEE probe, although no patients required treatment of these iatrogenic injuries. Probe insertion with direct visualization probably reduces the rate of hypopharyngeal injury. More serious complications, such as esophageal perforation, although fortunately rare, may occur more often than previously believed. In a recent study of more than 15,000 intraoperative TEE examinations, investigators reported 6 gastric or esophageal tears and 8 esophageal perforations, yielding an overall serious complication rate of about 1 in 1000 intraoperative examinations. Another study identified 7 esophageal perforations in more than 22,000 TEE examinations; 3 of those 7 patients died, giving an overall mortality rate of 0.014%.

Anatomic correlations

Irrespective of the reason for the TEE study, a comprehensive examination is recommended for every patient, preferably before focusing on a specific question or application of TEE. It is beyond the scope of this brief description to detail all the anatomic views obtainable with TEE, and the reader is referred to other reviews of the subject.

Intraoperative image orientation

Transducer location and the near field (vertex) of the image sector are at the top of the display and far field at the bottom. At a multiplane angle of 0 degrees (horizontal or transverse plane), with the imaging plane directed anteriorly from the esophagus through the heart, the patient’s right side appears in the left of the image display.

Basic probe movements

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