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The intraoperative echo exam shows severe aortic stenosis from exstensive calcification. The mitral valve has mitral annular calcification and moderate mitral stenosis. The LVEF is normal. The AVG and Vmax indicated moderate aortic stenosis. The calculated AVA is 0.29 cm2 and the measured AVA by 2D is 0.488 cm2. The mitral valve area by 2D is 1.14 cm2. The MVA DT is 377 msec or 595 msec (depending on which slope you are measuring) for a calculated MVA of 2.01 cm2 and 1.27 cm2 respectively. The mean MVG was 3 mmHg.
The preoperative TTE shows a mAVG of 30 mmHg which is moderate aortic stenosis. Also, the AVA calculates to 0.89 cm2 which is severe aortic stenosis. AVG is flow related and since the patient has restricted flow from mitral stenosis the gradient would tend to be lower from a decreased cardiac output. The
Mitral stenosis can be diagnosed by 2D planimetry, Doppler derrived mean MVG and PHT, and mitral valve area from calculations involving PISA and the continuity equation. 2D has the advantage of no flow or confounding factor assumptions but the disadvantage of having a good orifice image to measure and the plane to the narrowest mitral valve opening must be caught in a non-foreshortened view. 3D echocardiography will improve the accuracy of the interrogation plane. MVA by PHT can be calculated using CWD. However, sometimes (as in this case) the deceleration limb of the E wave is bimodal where it is usually rapidly decelerating in early diastole and then a slower deceleration occurs in mid diastole. The recommendation is to use the mid-diastolic wave in the calculations of PHT. The deceleration phase of the E wave depends upon the MVA, diastolic function of the left ventricle, left atrial compliance, and left ventricular compliance. Aortic regurgitation decreases the PHT measurement whereas impaired LV diastolic function can cause a variable effect. Early LV diastolic dysfunction can prolong PHT but decreased LV compliance can decrease the PHT. Therefore, in severe aortic stenosis the PHT should not be used because it is unreliable.
Aortic stenosis calculations such as aortic valve gradient are depending upon the cardiac output which is impaired in mitral stenosis. Significant mitral stenosis can lower the cardiac output and, therefore, falsely lower the aortic valve gradient.
In this case, the mean MVG was 8 mmHg preop, 3 mmHg intraop, and 7 mmHg postop. The MVA was 2.47 cm2 preop, 1.14 cm2 intraop, and 2.47 cm2 postop. It appears the AVR had little effect on the MVA or MVG calcluations/measurements. Also, the intraop calculations indicated moderate mitral stenosis by MVA and no MS by MVG whereas the preop and postop TTE indicated the absence of MS by MVA, but moderate MS by gradients.
Since gradients are flow related, they were unreliable preoperatively and intraoperatively. Also, since PHT is unreliable in the presence of severe AS, the preop and intraop MVA by PHT (or DT) is also unreliable. It seems the most accurate measurement of the MVA was the 2D measurement intraoperatively. The TTE postoperatively should have had a reliable PHT and MVA calculation.
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