Simplified echocardiographic measurement of the mitral anulus.

Postmortem, clinical, and experimental observations suggest an approximate elliptical shape for the mitral valve anulus, limiting the accuracy of single-diameter measurements in estimating annular area and circumference. A detailed method has been reported which uses six apical echocardiographic views at 30-degree rotational intervals to measure the mitral anulus, providing results comparable with pathologic and experimental reports. Annular data from nine normal subjects and 18 patients with dilated cardiomyopathy were analyzed to test a simplified measurement procedure. Assuming an elliptical shape, mitral annular area (MAA) and mitral annular circumference (MAC) were calculated by means of major (usually corresponding to the four-chamber view) and minor diameters from two orthogonal apical planes. Assuming a circular shape, MAA and MAC were also estimated by means of single annular diameters obtained from both an apical four-chamber and a parasternal long-axis view. Systolic and diastolic points were analyzed together, providing an n = 54 in the linear regressions. The two-plane results in MAA and MAC were nearly identical to those from the six-plane method, with very close correlation (r = 0.982 to 0.990). The single-plane results systematically overestimated MAA and MAC, with less correlation (apical, r = 0.943 to 0.963; parasternal, r = 0.852). Thus, while single-diameter measurements may correlate with global changes in annular size, the two-plane method represents a simplified but accurate method for estimating MAA and MAC in humans.