**2. Visualization of aortic valve**

The aortic valve is most clearly visualized in midesophageal aortic valve long- and shortaxis view through the left atrium as an acoustic window (Fig. 1a,b). Aortic regurgitation is readily assessed in the former, and every cusp and the sinus of Valsalva are visualized in the latter. Because the direction of blood flow is nearly perpendicular to the ultrasound beam in both views, Doppler measurements as an assessment of the pressure gradient in aortic stenosis cases are done in transgastric long-axis view (Fig. 1c) with minimal incident angle.

Due to the bulbar shape of the cusps and the sinus of Valsalva, visualization is limited in two-dimensional imaging of the aortic valve. 3D TEE is useful for visualizing all three cusps in a single view as well as surrounding structures such as the coronary artery and the sinus of Valsalva (Fig. 1d).

Fig. 1. Basic imaging of aortic valve. a: midesophageal aortic valve (AV) long-axis view; b: midesophageal aortic valve short-axis view; c: transgastritic long-axis view, d: 3D TEE view from the aortic side. AAO: ascending aorta, LA: left atrium, LCC: left coronary cusp, LV: left ventricle, NCC: noncoronary cusp, RCC: right coronary cusp
