Study on the characteristics of mitral annular displacement in middle and late pregnancy fetuses based on speckle tracking imaging

Objective To assess the longitudinal mitral annular plane systolic excursion (MAPSE) of different directions in normal fetuses during mid-late pregnancy based on two-dimensional speckle tracking imaging (STI). Methods Seventy-six normal fetuses during middle and late pregnancy were selected at 26-32 weeks of gestation. The peak MAPSE was measured by free angle M-mode echocardiography (FAM) perpendicular to the lateral annulus in the mitral annular plane. The time-displacement curves of interventricular septal mitral annulus in three different directions including points A, B and C through transverse level of apex were recorded by STI. The peak MAPSE of interventricular septal mitral annulus (SEPT-MAPSE-A, SEPT-MAPSE-B, SEPT-MAPSE-C) in three different directions including points A, B and C and the time to peak (TTP: SEPT-TTP-A, SEPT-TTP-B, SEPT-TTP-C) were recorded respectively. The time-displacement curves of lateral mitral annulus in three different directions including points A, B and C through transverse level of apex were recorded by STI. The peak MAPSE of lateral mitral annulus (LAT-MAPSE-A, LAT-MAPSE-B, LAT-MAPSE-C) in three different directions including points A, B and C, the time to peak(LAT-TTP-A, LAT-TTP-B, LAT-TTP-C) were recorded respectively. Finally, the data were analyzed statistically. Results The peak MAPSE of the lateral mitral annulus in 3 different directions including points A, B and C[LAT-MAPSE-A (3.62±1.01)mm, LAT-MAPSE-B (3.95±1.04)mm, LAT-MAPSE-C (4.45±1.05)mm] were greater than those of the interventricular septum mitral annulus[SEPT-MAPSE-A (3.41±0.63)mm, SEPT-MAPSE-B (3.07±0.50)mm, SEPT-MAPSE-C (2.82±0.51)mm]. LAT-MAPSE-C and SEPT-MAPSE-A were the largest longitudinal excursions of mitral annulus. The differences were statistically significant in points B and C (P 0.05). LAT-MAPSE-C was less than FAM-MAPSE[(6.06±1.35)mm]. There was a significant difference between them(P 0.05). There were no significant differences in time to peak of lateral mitral annulus[LAT-TTP-A(0.210±0.008)s, LAT-TTP-B(0.213±0.006)s, LAT-TTP-C(0.210±0.007)s] in directions inclucling points A, B, C(P>0.05). Conclusions Longitudinal systolic motion of fetal left ventricular wall during mid-late pregnancy has good synchronization. Longitudinal motion of fetal mitral annulus is a comprehensive movement of multiple directions and different degrees of displacement, with the movement perpendicular to the annulus as the maximum displacement direction. The displacement parameters of mitral annulus measured by STI can reflect the left ventricular longitudinal systolic function and have clinical application value in evaluating the left ventricular longitudinal systolic function of fetuses. Key words: Speckle tracking imaging; Fetus; Mid-late pregnancy; Mitral annular plane systolic excursion; Free angle M-mode echocardiography