Real-time sector scan study of the mitral valve prolapse syndrome.

Real-time two-dimensional sector sanning was used to analyse mitral valve motion in 4 normal subjects and 6 patients with previously diagnosed mitral valve prolapse syndromes. The normal mitral valve leaflets remain apposed for the duration of systole, and open abruptly with the onset of diastole. During diastole the leaflets are parallel to each other and only the distal ends tend to 'float' closed. Atrial contraction bows the anterior leaflet anteriorly which thus encroaches on the left ventricular outflow tract. The leaflet tips again 'float' closed, but the major portion of the leaflets are not closed until onset of the succeeding left ventricular isovolumic contraction. The abnormal redundant tissue of the ballooning mitral valve is seen as a prominent structure immediately behind the posterior leaflet at the beginning of systole. In one patient with the time-motion pattern of pansystolic prolapse this redundant tissue moved posteriorly in systole and appeared to merge with the left atrial wall. Of the remaninng 5 patients, 4 with late systolic prolapse had characteristic movements of this abnormal tissue. With the beginning of systole the redundant tissue moved superiorly and slightly anteriorly into the left atrium. In mid-systole at the time of the diagnostic changes in the standard time-motion study, the abnormal mitral valve tissue moved posteriorly and inferiorly to a position adjacent to the left atrial wall, and then at end-systole moved anteriorly to a mid-atrial position. During diastole the redundant tissue again moved posteriorly, and then again anteriorly to assume its mid-atrial position at the start of the next cardiac cycle. Hence, in at least some patients, the primary abnormality in the mitral valve prolapse syndrome is the mitral valve and not the left ventricle. There is definite prolapse of mitral valve tissue into the left atrium in this syndrome, and the prolapse appears to persist throughout systole regardless ofthe diagnostic pattern recorded with standard time-motion echocardiography. Furthermore, the redundant mitral valve tissue is the source of several distinct echoes which all follow the outlined course, thus accounting for the multiple parallel systolic echoes often observed in patients with the mitral valve prolapse syndrome.