![]() However, the mean gradient is related not only to mitral valve area but also to other factors that influence transmitral flow rate, such as heart rate, cardiac output, and associated mitral regurgitation. ![]() Therefore, the mean gradient is the most relevant haemodynamic parameter in patients with mitral stenosis. The peak gradient derives from peak velocity, which is influenced by left atrial compliance, left ventricular diastolic function, and loading conditions. This estimation is reliable, as shown by the good correlation with invasive measurement. Which allows highly accurate and reproducible calculation of peak pressure gradient (from peak velocity) and mean pressure gradient (that represents the mean of multiple instantaneous pressure gradients). In clinical practice, the transmitral pressure gradient can be estimated non-invasively by measuring transmitral flow velocity with CW Doppler echocardiography and by applying the simplified Bernoulli equation: However, the mean pulmonary artery wedge pressure is an indirect measure of the left atrial pressure, thus the mean pulmonary artery wedge pressure/left ventricular pressure gradient frequently overestimates the true severity of mitral stenosis. For practical reasons, in most cardiac catheterisation laboratories, evaluation of the transmitral gradient is frequently made with simultaneous pulmonary artery wedge pressure and left ventricular pressure. The most accurate way of determining the mitral valve gradient is the simultaneous recording of left atrial pressure provided by the transseptal technique together with left ventricular pressure obtained by retrograde catheterisation of the left ventricle. In pure mitral stenosis, the blood flow from the left atrium into the left ventricle is impaired, resulting in a pressure gradient between the two chambers during diastole. The assessment of mitral stenosis relies on measurement of the pressure gradient and on calculation of the valve area. Haemodynamic assessment of mitral stenosis The distance that this flow disturbance propagates downstream is related to stenosis severity. Distal flow disturbanceĭistal to the stenotic region, the flow becomes disorganised with multiple blood flow velocities and directions. As a rule, the narrowest cross-sectional area of flow (physiologic orifice area) is smaller than the anatomic orifice area. The flow profile in cross-section at the origin of the jet is relatively flat and remains flat as the jet reaches the vena contracta which is the narrowest cross-sectional area slightly downstream from the anatomic orifice. Stenotic areaĪt the level of the narrowed stenotic orifice, the fluid dynamics are characterised by the formation of a laminar high-velocity jet. Thus the proximal velocity profile of an atrioventricular valve is hemi-elliptical. This produces a curved three-dimensional flow profile. In patients with mitral stenosis, the left atrium to left ventricle pressure gradient drives flow passively from the large inlet chamber (the left atrium) abruptly across the stenotic orifice. The spatial flow velocity profile proximal to a stenotic valve depends on valve anatomy, inlet geometry, and the degree of flow acceleration. The mitral stenosis jet is long, with the post-jet disturbance occurring adjacent and distal to the laminar jet. The stream lines of flow accelerate as they approach the stenotic orifice, with several curved proximal isovelocity surface areas. MITRAL STENOSIS Fluid dynamics of mitral stenosis (Figure 1)įigure 1.
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