DK2985_C000 1..28 - AlSharqia Echo Club

86 Transesophageal Echocardiographyestimation of valve area by the continuity equation. Again,transgastric views at 60–908 can be used to obtain thesevalues (Figs. 4.10 and 4.24). The pulmonic maximalgradient can also be measured from above the valve bycontinuous-wave Doppler interrogation through the upperesophageal position looking down the main pulmonarytrunk at 08 (Figs. 4.14 and 5.16) or 908 (Fig. 19.5).H. Left Ventricular Outflow TractSee Section I.B.1, Figs. 4.36 and 5.29[A].I. Pulmonary VeinThe right and left upper pulmonary veins usually presentthe best alignment for pulsed-wave Doppler interrogation,with the sample volume positioned approximately 1 cminside the vein from the ostium (Figs. 4.21–4.23).Normal pulmonary venous flow is multiphasic, with twopeaks in systole (S 1 and S 2 ), one peak in diastole (D)and one retrograde peak during atrial contraction, calledatrial reversal (AR). The S 1 is related to atrial relaxationand may be proportional to the magnitude of atrialsystole and therefore the AR wave. The S 2 velocity isinfluenced by the suction of blood from the pulmonaryveins with LA expansion secondary to the mitral valveannulus descent during ventricular systole and to RV contraction.The diastolic velocity (D) depends on the LApressure drop after the MV opening, and also on theLA–LV pressure gradient.With normal LV filling pressures, there is more pulmonaryvenous flow in systole than in diastole, with theS/D ratio .1. In the case of a young adult with excellentventricular relaxation, a S/D ratio ,1 may be observed.The AR wave duration may also exceed the duration ofthe mitral A wave, but never by .30 ms with normalleft-sided filling pressures. In the case of abnormallydecreased LV compliance or elevated LA or LV fillingpressures, such as in moderate-to-severe MR or significantLV systolic or diastolic dysfunction, there will be diastolicflow prominence (S/D , 1). Severe MR can even causesystolic flow reversal.Elevated LV end-diastolic pressures during atrial contractioncause preferential blood backflow in the pulmonaryveins rather than downstream through the mitral valve.This leads not only to increased AR velocity but also ARduration exceeding that of the mitral A wave by .30 ms(see Chapter 9).J. Hepatic VeinThe hepatic veins are the equivalent of the pulmonaryveins for the right heart (Fig. 4.25). Similarly, thehepatic venous Doppler flow is multiphasic, with systolic,diastolic, and atrial reversal waves. However, with operatingpressures on the right heart lower than on the left, thereis often some mild systolic flow reversal before diastolicflow. The S/D ratio is usually .1 with normal rightsidedfilling pressures (see Chapter 9).When the right-sided filling pressures are elevated,normal systolic flow prominence may be lost with,occasionally, even an absence of forward flow duringsystole. In such cases, the S/D ratio will be inverted(,1) (see Chapter 9). Tamponade physiology can alsobe accompanied by abnormal expiratory diastolic flowreversal (see Chapter 11).K. Ascending AortaAs stated earlier in the evaluation of AS, maximal aorticvelocity and pressure gradient should be sought from ahigh esophageal window looking down the distal ascendingaorta even if this is not always achievable because ofinterference from the air-filled trachea (Fig. 4.32).L. Descending Aorta-FlowReversal and AorticRegurgitationAlthough the descending thoracic aorta easily lends itselfto 2D examination because of its very close proximity tothe esophagus, the direction of aortic flow is howeveroften perpendicular to the direction of the ultrasoundbeam of the TEE probe. Therefore, precise measurementsof the descending thoracic aorta pressure gradient (forcoarctation evaluation, for instance) are usually precluded.Likewise, assessment of AR severity with measurement ofthe duration, velocity, and time–velocity integral of thediastolic flow reversal may be harder to achieve than byTTE (see Chapter 15).M. Coronary SinusCoronary sinus Doppler examination is best conductedfrom the lower esophageal sphincter position while withdrawingthe probe from the transgastric to the esophagealposition in the longitudinal plane at 908. As the coronarysinus in its short axis is centered over the display, theprobe shaft is then rotated rightward towards the orificeof the coronary sinus in the RA. Most often the coronarysinus will then be imaged in its long axis, with the coronarysinus flow going away from the probe (Fig. 4.26).Coronary sinus flow is similar to multiphasic right-sidedvenous flow.