Figure 33-13 Continuous-wave Doppler estimation of the aortic valve (AV) gradient. Continuous-wave Doppler measurement of blood flow velocities immediately above the AV during seven cardiac cycles is shown. At the top of the figure is a still-frame image of the two-dimensional cross section used to position the Doppler sample cursor (the diagonal white line). 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 provides timing, and the bold horizontal line is the baseline (zero flow) for the flow velocities. With this Doppler alignment, all flow velocities are negative (i.e., away from the transducer). The Doppler scale has been set to a maximum of -629 cm/sec, and this tracing documents significant aortic stenosis: a peak blood flow velocity of approximately 4 m/sec (each white dot on the vertical axis equals 100 cm/sec or 1 m/sec) corresponding to a peak gradient across the aortic valve of 64 mm Hg. (From Cahalan MK: Intraoperative Transesophageal Echocardiography. An Interactive Text and Atlas. New York, Churchill Livingstone, 1997.)