The vena contracta is the narrowest portion of the regurgitant flow that occurs at or immediately after (downstream of) the regurgitant orifice (in the case of aortic regurgitation, the aortic valve).

which is manometrically measured as aortic pressure. This physical phenomenon is called "pressure recovery", which is generally, 5-10 mm Hg higher than pressure in "vena contracta." In other words ...