Which technique best determines a trileaflet aortic valve from a bicuspid aortic valve?

The most reliable technique to distinguish a trileaflet aortic valve from a bicuspid valve is to visualize all three leaflets simultaneously during diastole when the valve is closed. During diastole, the aortic valve leaflets coapt, and the three cusps form a characteristic “Y-shaped” or “Mercedes-Benz” sign on short-axis echocardiographic views, clearly demonstrating the number of leaflets.

Visualization during systole is less reliable because the valve is open, and the leaflets are moving rapidly. Doppler techniques (pulsed or continuous wave) assess flow velocities but do not definitively determine leaflet number, only stenosis severity.

This approach is well documented in adult echocardiography textbooks and ASE valvular imaging guidelines, which emphasize the diastolic short-axis view for valve morphology assessment【16:Textbook of Clinical Echocardiography, 6e†p.190-195】【12:ASE Valve Imaging Guidelines†p.180-185】.