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Figure 19-16. Pressure recovery. Schematic representation of velocity and pressure changes from the LVO tract to the ascending aorta (AA) in the presence of a stented bioprosthesis and a bileaflet mechanical valve illustrating the phenomenon of pressure recovery. Because of pressure recovery, velocities are lower and systolic arterial pressure (SAP) is higher at the distal aorta than at the level of the vena contracta (VC). This is further exaggerated in the case of a bileaflet valve, in which the velocity is higher in the central orifice (CO) and thus pressure drop is higher at that level. Doppler gradients are estimated from maximal velocity at the level of the vena contracta and represent the maximal pressure drop, whereas invasive estimation of gradients usually reflect net pressure difference (&Dgr;P) between LV systolic pressure (LVSP) and ascending aorta. LO, Lateral orifice; SV, stroke volume in LVO. (From Zoghbi WA, Chambers JB, Dumesnil JG, et al. Recommendations for Evaluation of Prosthetic Valves With Echocardiography and Doppler Ultrasound: A Report From the American Society of Echocardiography’s Guidelines and Standards Committee and the Task Force on Prosthetic Valves. J Am Soc Echocardiogr. 2009;22(9):975-1014; quiz 1082-1084.) |