Vena Contracta: The narrowest point of a regurgitant color Doppler jet at the valve orifice; width ≥7 mm for MR or ≥6 mm for AR indicates severe valvular regurgitation.
The vena contracta is the narrowest cross-sectional diameter of a regurgitant jet as it passes through an incompetent valve orifice, measured on color Doppler echocardiography. It directly reflects the effective regurgitant orifice area (EROA). For mitral regurgitation, vena contracta ≥7 mm indicates severe MR. For aortic regurgitation, ≥6 mm indicates severe AR. It is less dependent on loading conditions than jet area.