UNDERSTANDING ECHOCARDIOGRAPHIC ANATOMY
A transesophageal ultrasound probe used for echocardiography can flex forward and backward as well as side-to-side. Imagine the ultrasound beam as flat triangle emitted from the probe. This triangle can rotate 180° around its top point allowing the echocardiographer to view different images or slices of the heart at a particular depth in the esophagus or stomach. The degree of rotation is the “omniplane.” Zero degrees on the omniplane will provide cross-sectional axial images while 90° will provide sagittal images. The omniplane degree is indicated by a semicircle symbol located on the echocardiography image.
The heart lies in the mediastinum slightly rotated to the left so that the left atrium abuts the esophagus and the right atrium and ventricle are the most anterior. The key to deciphering cardiac echocardiography anatomy is to remember that in the esophagus the first hypoechoic structure is almost always the left atrium. From that starting point, other structures will be more easily identified. Also, note the relationship of the great vessels to each other. The aortic arch arches over the right pulmonary artery and almost overlies the main pulmonary artery. These great vessels lie perpendicular to each other meaning that when one is seen in axial cross-section, the other will be seen in its longitudinal axis. Finally, note the close relationship of the superior vena cava immediately adjacent to the ascending aortic arch.
BASIC TRANSESOPHAGEAL ECHOCARDIOGRAPHY VIEWS
For the basic 11 TEE views, the esophageal probe will be placed in the midesophagus (either at the level of the aortic valve or just below it) or into the stomach to obtain a transgastric view.
Midesophageal ascending aorta short-axis view—As the probe descends down the esophagus, the first structure visualized is the aortic arch. Advancement of the probe past the aortic arch and rotation toward the patient’s right enables visualization of the ascending aortic arch (Figure 51-1). The first hypoechoic structure is clearly not the left atrium. When two large vessels are seen with one in cross-section and the other in a longitudinal view, it is a safe bet that the vessels are the aorta and pulmonary artery. At 0° omniplane, the image must be showing an axial view of the anatomy. Unless the probe is at the aortic arch, an omniplane of 0° will always show the aorta in its short axis. The other large vessels are the right and main pulmonary artery. Note the superior vena cava immediately abutting the ascending aorta.
Midesophageal ascending aorta long-axis view—At the midesophageal ascending aorta short axis view, increasing the omniplane to 120° yields two hypoechoic structures (Figure 51-2). The first hypoechoic structure cannot be the left atrium due to the underlying soft tissue and its shape. The two vessels perpendicular to each other are the aorta and pulmonary artery (in this case the right pulmonary artery). ...