Schematic transthoracic echocardiography-based short-axis, base-of-the-heart anatomical landmarks and clock face for bicuspid aortic valve diagnosis and phenotyping. (Left panel) Schematic of the normal tricuspid aortic valve in the echocardiographic parasternal short-axis view, applicable to similar views obtained with cardiac computed tomography and cardiac magnetic resonance. The right coronary cusp (small R) is anterior and positioned between the TV and PV insertions. The left coronary cusp (small L) is posterior-lateral and related to the LA, whereas the non-coronary cusp (small N) is the most posterior and related to the IAS. Note the origin of the coronary arteries at the right and left cusps. These landmark anatomical relations of each cusp relative to adjacent structures are critical in determining which 2 cusps are fused. Modified from Michelena et al. [10] with permission from Elsevier. (Right panel) The annular circumference of the aortic valve can be visualized like the face of a clock. Fused bicuspid valves with right–left cusp fusion usually have commissures at 4 and 10 or 5 and 11 o’clock (see Figs 6 and 7), and the anatomy relative to adjacent structures suggests right–left cusp fusion. In right non-coronary cusp fusion, the commissures are usually at 1 and 7 or 12 and 6 o’clock (see Figs 6 and 7); the anatomy relative to adjacent structures suggests right non-cusp fusion. In left non-coronary cusp fusion, usually 2 and 8 or 9 and 3 o’clock (see Figs 6 and 7) and the anatomy relative to adjacent structures suggest left non-fusion. It is important to note that there can be overlap between the clock positions; thus, it is critical to know the landmark anatomical relations of each cusp. Identification of the raphe can be invaluable in determining the conjoined cusp. Identification of the origin of the left and right coronary arteries (left panel) may also be invaluable. IAS: interatrial septum; LA: left atrium; large L: left side of the patient; large R: right side of the patient; P: posterior aspect of the heart; PA: pulmonary artery; PV: pulmonary valve; RA: right atrium; RVOT: right ventricular outflow tract; TV: tricuspid valve. Modified from Michelena et al. [10] with permission from Elsevier.