[The systolic slipping mechanism of the anterior mitral leaflet in patients with the straight back syndrome].

The systolic slipping mechanism of the anterior mitral leaflet in patients with the straight back syndrome (SBS) was evaluated by two-dimensional echocardiography in 16 SBS patients and 11 normal subjects. Doppler echocardiography was performed in all subjects to detect mitral regurgitation. The site of the mitral slipping was identified in a centromedial region of the anterior mitral leaflet in these patients. The ellipsoidal index (long axis/short axis) of the left ventricle was greater in SBS patients than in normal subjects. The left ventricular wall had a characteristic motion in SBS. The lateral wall contracted well, while the posterior septum and inferoposterior wall were hypokinetic. Moreover, the anterolateral papillary muscle moved horizontally during systole, while the posteromedial papillary muscle moved anteriorly. There was a significant correlation between the distance of slipping of the anterior mitral leaflet and the PL/PM ratio (r = -0.39, p less than 0.001), where PL is the distance from the gravity point of the left ventricle to the midpoint of the anterolateral papillary muscle, and PM is that from the gravity point of the left ventricle to the posteromedial papillary muscle. Mild mitral regurgitation was identified in four cases with SBS by Doppler echocardiography, and this regurgitant jet was directed from the posterior mitral leaflet to the posterior wall of the left atrium. These results suggest that the systolic slipping of the anterior mitral leaflet in SBS might be caused by asynchronous papillary muscle motion. This might be based on the ellipsoidal left ventricle due to the short internal dimension of the thorax.(ABSTRACT TRUNCATED AT 250 WORDS)