can be adjusted with buttons or a dial, and this varies with the specific probe and ultrasound machine. Movement The probes often have one or two degrees of freedom: Flexion or retroflexion can point the crystal superiorly or inferiorly, respectively Left and right flexion tilts the probe left and right These two degrees are typically adjusted using dials on the handle of the probe. A third degree is axial rotation of the probe (clockwise or counter-clockwise) and is present regardless of the other two degrees of freedom. A fourth degree is the translation of the probe long its axis to permit passing through the mouth, into the esophagus, and into the stomach. The combination of these four degrees of freedom permit 2-D, color, and Doppler echo of practically every structure in the heart. Positions Transthoracic echo is far more commonly used than TEE and transthoracic echo is limited to by the available windows through the chest wall to visualize the heart. TEE does not have such discrete locations and can visualize the heart anywhere along the esophagus to the stomach. With that said, there are commonly accepted positions along this path that are used when performing a standard TEE. Midesophageal The midesophageal view is positioned posterior from the left atrium and at 0° this provides for a long-axis four chamber view. At 0°, the long-axis four chamber view can be obtained with slight retroflexion of the probe. However, slight rotation and insertion may be needed to better visualize the right heart and tricuspid valve. At 45°, the short-axis view of the aortic valve can be obtained. At this angle, a short-axis view of the right ventricle can be seen to visualize the right atrium, tricuspid valve, right ventricle, and pulmonary valve in a single view. At 90°, the probe can be rotated clockwise to obtain the "bicaval view" in which the right atrial and both the inferior and superior vena cava can be viewed. At 135°, the long-axis view of the aortic valve can be obtained. The left atrial appendage, with proper probe positioning, can be visualized at all angles and often visualized at 0*, 45°, 90°, and 135° to adequately rule out a thrombus. Transgastric Pushing the TEE probe past the gastroesophageal junction into the stomach and flexing the probe (pointing it toward the superior) yields a short-axis view of the heart. At 0°, the short-axis of the left