The quantification of hemodynamics by Doppler echocardiography using transesophageal windows may be useful in providing rapid information useful in the acute management of some patients. Three main equations form the basis of hemodynamic calculations: the flow equation, the Bernoulli equation, and the continuity equation. According to the continuity equation, the blood flow entering a cardiac chamber in diastole is equal to the blood flow leaving that chamber in systole. If people apply this concept to regurgitant valves, they can measure the volume of the regurgitant blood during the cardiac cycle. The assessment of the severity of regurgitant valves is more complex. The vena contracta, the area of the regurgitant jet, and the proximal isovelocity surface area (PISA) method may be useful. The data obtained should always be interpreted with caution and in association with data obtained from other modalities.