Figure 3: Measurement of PA flow- short axis of aortic valve level. Pulmonary artery flow is measured by a pulse wave Doppler. At the aortic valve level in the short axis view, pulmonary artery flow velocities were recorded and maximum pulmonary artery velocity (Vmax), acceleration time (AT) and ejection time (ET) of pulmonary artery flow velocity tracing were measured, and the ratio of AT to ET (AT/ET) was calculated.