Figure 33-5 Continuous-wave Doppler measures high-velocity flow without aliasing. Continuous-wave Doppler measurement of blood flow velocities in a mitral valve orifice during four 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 all 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. Flow velocities above this line are positive (i.e., toward the transducer) to a maximum of 753 cm/sec. Flow velocities below this line are negative (i.e., away from the transducer) to a maximum of -316 cm/sec. This tracing documents significant mitral regurgitation (the positive systolic velocities) with a peak blood flow velocity of approximately 5 m/sec (each white dot on the vertical axis equals 100 cm/sec or 1 m/sec). LA, left atrium; LV, left ventricle. (From Cahalan MK: Intraoperative Transesophageal Echocardiography. An Interactive Text and Atlas. New York, Churchill Livingstone, 1997.)