Calculation of mitral valve area from continuous wave Doppler

The mitral valve area can be obtained from the continuous wave Doppler by calculating the time required for the opening pressure to reach one half of its value (P 1/2); this is called P 1/2 time and is calculated as shown. By regression analysis, a critically stenotic valve measuring 1 cm² has a pressure half time of 220 ms; the valve area can be calculated as shown above.