Q. Illustrate Mitral Valve Orifice Area?

The normal mitral valve orifice in an adult is 4-5cm² when the valve is completely open in diastole. When the mitral valve orifice area is 1.0 cm², then there will be a significant resting gradient across the valve and any requirement for increase cardiac output leads to an increase in LA and PCW pressure and results in Pulmonary edema. This therefore, represents "critical mitral valve orifice area".

The formula for calculating mitral valve orifice area is:

Where P = mean transmitral pressure gradient, and MVA = mitral valve area. Thus when the cardiac output is doubled, the transmitral gradient is quadrupled (if HR and DFP remain constant).