Aortic valve area can be measured by cardiac catheterization, Doppler echocardiography, or imaging planimetry to assess aortic stenosis severity. These diagnostic techniques provide the Gorlin area, the effective orifice area (EOA) and the geometric orifice area (GOA), respectively. The differences between these three parameters depend mainly on the valve inflow shape and cross-sectional area of the ascending aorta. Because the values obtained may differ noticeably in the same patient, they may lead to different estimations of stenosis severity depending on the measurement method used. It is therefore essential to be aware of the underlying fundamentals on which these parameters are based. The aim of this state-of-the-art report was to clarify these hemodynamic concepts and to underline their clinical

implications. Because planimetry only provides GOA and does not characterize the flow property, this method should preferably not be used to assess stenosis severity. The most appropriate parameters for this purpose are the Gorlin area and the energy loss coefficient (ELCo), which corresponds to the EOA adjusted for aortic cross-sectional area. From a hemodynamic viewpoint, Doppler ELCo and Gorlin area both reflect the fluid energy loss induced by aortic stenosis, and describe better the increased overload imposed on the left ventricle. Although the Gorlin area and Doppler ELCo are equivalent, the latter parameter has the advantage of being measurable non-invasively using Doppler echocardiography.

The Journal of Heart Valve Disease 2006;15:601-608