Figure 33-14 Continuous-wave Doppler evaluation of mitral stenosis. Continuous-wave Doppler measurement of blood flow velocities through a stenotic mitral valve is shown. At the top of the figure is a still-frame image of the four-chamber cross section used to position the Doppler cursor. On the bottom two thirds of the figure is the display in white of the instantaneous blood flow velocities (vertical axis) versus time (horizontal axis) occurring anywhere along that cursor. The electrocardiogram is shown for timing purposes, and the red horizontal line running through the Doppler tracing is the baseline (zero flow) for the flow velocities. Velocities displayed above the baseline are positive and represent flow toward the transducer. These velocities are due to mitral regurgitation and are so high that they exceed the scale used in this example. Velocities displayed below the baseline are negative and represent flow away from the transducer. These velocities are due to severe mitral stenosis and average about 2 m/sec, which is indicative of a gradient across the mitral valve of 16 mm Hg. Also note how slowly the flow velocity decreases after the peak of the E wave (indicated in the figure by "Slope"). The pressure half-time can be calculated from this slope and is markedly increased in the presence of severe mitral stenosis. (From Cahalan MK: Intraoperative Transesophageal Echocardiography. An Interactive Text and Atlas. New York, Churchill Livingstone, 1997.)