Obtain a PWD or a CWD of the mitral valve. The flow profile of the mitral valve will have a Vmax, typically the maximum velocity of the E wave. The time from the Vmax to the where the velocity is equal to zero is the deceleration time. Typically, the curve will have to be extrapolated to the zero velocity. The mitral valve area is equal to 759 divided by the deceleration time.