Figure 33-1 M-mode transesophageal echocardiogram of a normal aortic valve. For reference, a single frame (stop action) of the two-dimensional cross section is shown at the top right of the figure. The dotted vertical line through the two-dimensional echocardiogram depicts the single line of sampling provided by the M-mode echocardiogram over time (the horizontal axis for the lower two thirds of the figure). The electrocardiogram defines systole and diastole. Note in the middle of the M-mode image the three tilted rectangles connected by the slightly undulating line. These rectangles and lines are formed by the motion of the leaflets of the aortic valve as they open and close during the cardiac cycles shown. From top to bottom in this M-mode echocardiogram, the structures indicated by the white lines are the posterior wall of the left atrium (just under the electrocardiogram), the posterior wall of the aortic annulus, the aortic valve (as described above), the anterior wall of the aortic annulus, a pulmonary artery catheter, and the myocardium of the right ventricular outflow tract. (From Cahalan MK: Intraoperative Transesophageal Echocardiography. An Interactive Text and Atlas. New York, Churchill Livingstone, 1997.)