DK2985_C000 1..28 - AlSharqia Echo Club

420 Transesophageal Echocardiography(A)(B)LARALVRV(C) Max Vel: 218 cm/secMn Vel: 143 cm/secVTI: 101 cmMax PG: 19 mmHgMn PG: 8.9 mmHg(D)Figure 18.4 A 79-year-old woman was reoperated for bioprosthetic mitral valve stenosis and regurgitation. (A, B) A mid-esophagealfour-chamber view shows the mitral regurgitant jet and acceleration through the orifice. (C) A mean pressure gradient of 8.9 mmHg ismeasured with continuous-wave Doppler. (D) Intraoperative examination of the valve revealed severe stenosis (LA, left atrium; LV, leftventricle; Max, maximum; Mn, mean; PG, pressure gradient; RA, right atrium; RV, right ventricle; Vel, velocity; VTI, velocity–timeintegral). (Photo D courtesy of Dr. Michel Pellerin.)prostheses, it symmetrically curves around the ball while intilting disk prostheses, color flow is seen through the threeorifices. Two-dimensional and color flow imaging are usedto guide the CW Doppler cursor in order to ensure optimalalignment of the ultrasound beam with the direction of thejet. The peak gradient is determined from the maximalDoppler flow velocity with the simplified Bernouilliequation: P ¼ 4v 2 where P is the pressure in mmHg andv is the velocity in m/s. As for native mitral valves, themean transprosthetic gradient is obtained, by tracing the diastolicCW Doppler signal (Fig. 18.5) which calculates themean of the squared instantaneous velocities. Measurementof mean gradient is more important because it representsthe gradient between the left atrium (LA) and the left ventricular(LV) throughout diastole.The gradient evaluation must take into account theprosthetic valve type and size, as well as the heart rate(HR) and cardiac output (CO). In the adult population,the mitral transprosthetic gradient is, however, generallyless dependent on the sewing ring size than for aortic prostheses.At normal heart rates, the normal mean diastolicgradient of mechanical mitral valves is 4–6 mmHg andfor bioprostheses it is 3–5 mmHg. As with nativevalves, the gradient is increased with tachycardia. Pressurerecovery may also be associated with increased gradientwithout intrinsic dysfunction. This is more commonlyseen with AoV prostheses but can occasionally occurwith mitral mechanical prostheses (5,6).Max Vel: 138 cm/secMn Vel: 96.3 cm/secVTI: 30.8 cmMax PG: 7.62 mmHgMn PG: 4.18 mmHgFigure 18.5 Measurement of the diastolic transvalvular gradientwith continuous-wave Doppler in a functional bileaflet St. Judemechanical prosthesis (Max, maximum; Mn, mean; PG, pressuregradient; Vel, velocity; VTI, velocity–time integral).