Valvular Dysfunction

TEE provides a highly reliable means for the assessment of valvular structure and function. Although a comprehensive review of this topic is beyond the scope of this chapter, a brief overview of the most commonly used techniques should prepare the reader to fulfill at least

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The degree of aortic stenosis is easily appreciated in the ME AV SAX cross section, where the extent of leaflet opening can be estimated visually or measured directly with planimetry.^[86] Severe stenosis is characterized by marked thickening of the leaflets and severely reduced leaflet motion (valve opening area <1 cm² ). In the deep TG LAX cross section, CW Doppler allows reliable estimation of the gradient across the AV ( Fig. 33-13 ).^[87] In severe stenosis, the peak instantaneous gradient will exceed 64 mm Hg (CW velocity exceeding 4 m/sec), provided that cardiac output has not been markedly compromised. Noteworthy is the fact that the echocardiographically derived AV gradient may be higher than the peak-to-peak gradient reported from a catheterization study because the latter does not measure the instantaneous gradient as Doppler echocardiography does. Additional information on the morphology of the AV, including the dimensions of the annulus, sinotubular junction, and ascending aorta, can be garnered from the ME AV LAX cross section. The degree of aortic regurgitation is appreciated best in this cross section. With color Doppler positioned over the leaflets and outflow track, aortic regurgitation is recognized as a color jet emanating from the valve during diastole. Even

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.)

The presence and severity of mitral stenosis are easily determined with TEE by using the ME four-chamber, two-chamber, commissural, and/or LAX cross section, as well as the basal TG SAX cross section. Two-dimensional imaging reveals thickened leaflets that dome toward the left ventricle and open poorly. Color Doppler reveals laminar flow acceleration into the stenotic orifice and a turbulent jet emerging into the ventricle ( Plate 33-3 ). PW and CW Doppler traces display a characteristic flow pattern with increased peak and mean velocities ( Fig. 33-14 ). Mathematical calculations from these traces, such as the pressure half-time, are the most precise methods to assess the severity of mitral stenosis, and formulas for these

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The presence and severity of mitral regurgitation are evaluated from the same cross sections used for evaluation of mitral stenosis and with the same grading strategy used for aortic regurgitation ( Table 33-7 ). Mild regurgitation is characterized by a narrow-based, systolic color jet (<2 mm at its origin in the valve) that occupies less than 25% of the left atrial cross-sectional area and extends less than half the distance to the posterior wall of the left atrium. Moderate regurgitation is a broader-based, systolic color jet (3 to 5 mm at its origin in the valve) occupying less than 50% of the left atrial cross-sectional area and extending 50% to 90% of the distance to the posterior wall of the left atrium. Severe regurgitation is a broad-based, systolic color jet (>5 mm) that occupies most of the left atrium and extends into the pulmonary veins and left atrial appendage ( Fig. 33-15 ). Eccentrically directed jets of mitral regurgitation that hug the wall of the atrium are generally associated with more severe valvular regurgitation than their cross-sectional area might suggest ( Plate 33-4 ). Moreover, eccentrically directed jets usually point away from the defective leaflet (i.e., laterally directed jets are generally associated with anterior leaflet defects and medially directed jets with posterior leaflet defects), provided that the mechanism of regurgitation is leaflet prolapse or flail.^[90] Severe mitral regurgitation is invariably associated with systolic reversal of pulmonary venous inflow.^[91] The general guidelines listed earlier are widely used, but many more criteria have been described for assessment of mitral regurgitation.^[92] Most importantly, the degree of regurgitation is exquisitely dependent on LV loading conditions. For practical purposes, quantitative measures of regurgitation, for example, the regurgitant orifice area based on the theory of proximal isovelocity surface area, are less often used in the operating room because of time restriction.^[49]

Pulmonary and tricuspid valve pathology is assessed in a fashion analogous to that described for the aortic and mitral valves.