Size and motion of the mitral valve annulus in man. I. A two-dimensional echocardiographic method and findings in normal subjects.

Using wide-angle, phased-array, two-dimensional echocardiography, mitral leaflets and their annular attachments were recorded from a view close to the standard apical four-chamber view. The transducer was rotated and recordings were made at 30 degrees rotational intervals around the circumference of the mitral valve annulus. To reconstruct the annulus, the diameters (chords) from each rotational interval were arranged around a reference point. This was done for 12 times during the cardiac cycle. Annular areas were planimetered and circumferences measured. Correlation was good for areas reconstructed and measured by the same observer on separate occasions (r = 0.963) and by two different observers (r = 0.987). In 11 normal subjects the annular area index (area divided by body surface area) increased during diastole to a maximum of 3.8 +/- 0.7 cm2/m2 (mean +/- SD) in late diastole. There was presystolic followed by systolic narrowing to a minimum in midsystole. The mean reduction in area was 26 +/- 3%. The maximal annular circumference was 9.3 +/- 0.9 cm and the mean reduction in circumference was 13 +/- 3%. The overall motion pattern was similar to that reported in experimental studies in the dog. Mitral annular reconstruction may provide new information about normal and abnormal function of the mitral valve apparatus.