Reliability and reproducibility of two dimensional echocardiograph measurement of the stenotic mitral valve orifice area.

Abstract A wide angle phased array sector scanner was used to find the optimal method, the reliability and the reproducibility of measuring the mitral valve area with two dimensional echocardiography in patients with rheumatic mitral stenosis. Initial experience with 18 patients revealed that tracing the early diastolic actual black-white interface of the perceived orifice was the most reliable method for drawing the mitral valve orifice area. Good interobserver correlation was obtained when two observers used either method to calculate the mitral valve area ( r = 0.93). Similarly good intrastudy reliability was obtained when any one observer applied one measurement method to different diastolic cycles within the same study ( r = 0.89). The phased array two dimensional echocardiogram properly differentiated patients with critical mitral stenosis from those with non-critical mitral stenosis, but the correlation between the echocardiographically and the hemodynamically derived mitral valve areas was less good than previously reported ( r = 0.83). Imaging a test object with varied known orifice sizes and excised stenotic mitral valves of known orifice size with a phased array and mechanical sector scanner failed to reveal superiority of either instrument. Further testing with a phased array instrument revealed that the perceived orifice was critically dependent on receiver gains settings for any transmitted power level. Receiver gain settings too low led to image dropout, indicating a falsely large orifice. Receiver gain settings too high led to image saturation, indicating a falsely narrowed orifice. Six additional patients with predominant mitral stenosis later underwent imaging with strict attention paid to individual receiver gain settings. Combining the data from these 6 patients with those from the initial 18 patients gave a better correlation between the echocardiographic and hemodynamic calculated mitral valve areas ( r = 0.92). Accurate noninvasive measurement of the mitral valve area with two dimensional echocardiography in patients with mitral stenosis appears to depend on use of the proper echocardiographic technique to localize the true commissural edge of the valve in early diastole, the correct instrument settings and the appropriate method for drawing the perceived orifice. The noninvasive measurement of the mitral valve orifice with two dimensional echocardiography in mitral stenosis provides clinically useful data that are reliable and reproducible if these factors are taken into account.