A study of orifice shape effects in the determination of mitral valve area by two-dimensional echocardiography.

Real-time two-dimensional echocardiographic studies of the mitral valve in short-axis view were obtained from 10 normal subjects. Stop-action frames of the video-taped echocardiograms were then photographed to obtain diastolic cross-sectional images of the valve at maximal opening. Tracings from the interior of the leaflet echoes were then digitized to provide the perimeter and area of the mitral orifice. From the perimetric data, boundary integration was used to numerically calculate the orifice area corresponding to an elliptical boundary, for aspect ratios ranging from 0.5 to 1.0 (circle). It was found that the mean orifice areas determined echocardiographically and numerically are equal for an aspect ratio of 0.42. For aspect ratios greater than this value, the elliptical areas are larger, while for smaller aspect ratios, the elliptical areas are smaller.