[Diagnosis of aortic stenoses by Doppler sonography]

Doppler sonography permits to diagnose the gravity of valvular aortic stenosis if absolute conditions of reliability of the method are respected. The Doppler examination must be performed by a physician particularly familiar with this technique because it is a difficult examination. Systematic trial of the 5 possible approaches of the aortic orifice must be required: apical, left and right parasternal, substernal and sub-xyphoid approaches. Only velocity curves with a well defined contour must be retained and the concordance of the maximal velocities obtained by apical and parasternal approaches is in favor of a good alignment of the ultrasound beam on the aortic flow. It must be remembered that any sub-aortic obstacle or severe aortic insufficiency simulates an aortic stenosis on a continuous Doppler and that it is necessary to resort to the pulsated Doppler to rectify the diagnosis: acceleration of the flow occurs therefore in the flush chamber of the left ventricle and not at the level of the sigmoid orifice. We will remember that the Doppler does not provide the peak to peak gradient seen in hemodynamics but the maximal instant gradient which is always higher than the first one, and more especially as the aortic stenosis is more moderate. The best criteria of gravity of an aortic stenosis remain the mean gradient and the valvular area: the mean gradient is easily deduced from the quadratic transformation of the Doppler velocity curve and from a simple planimetry. The valvular area is obtained by applying the continuity equation which permits to get rid nicely of the cardiac output but still requires more validation before becoming part of the routine.