Regional differences in MPI in the normal fetal heart – a Tissue Doppler echocardiography (TDI) study

Objective: An explorative study on regional differences in MPI in the normal fetal heart in the second trimester of pregnancy.

Materials and methods: In 20 fetuses without abnormalities in the second trimester screening between 19th and 24th week of gestation longitudinal four chamber view colour TDI cineloops of 3 cardiac cycles were recorded. Sample areas were in the subvalvulare plane, the middle segment and the apex of the myocardium of free walls of both ventricles and the interventriculare septum. Thus allowing the simultaneous measurement of myocardial velocities in different regions in the same heart cycle, thereby ICT, ejection phase and IRT could be measured to calculate MPI (MPI=(ICT+IRT)/ET).

Results: Highest values for MPI were measured in the apical segments (right ventricle 0.62; left ventricle 0.68), indicating lower myocardial performance compared to other regions in the fetal myocardium. MPI in the basal right ventricular free wall (0.48) was lower than in the left (0.55) (p=0.004) and the interventricular septum (0.52) (p=0.016), according to the right ventriculare dominance in the fetal heart. The same interventriculare gradient was found in the middle segments. MPI was lowest (0.44) in the middle segment of the right ventricular free wall, compared to 0.52 in the middle segment of the septum and 0.63 in the left ventricle, indicating highest myocardial performance compared to other regions.

Conclusion: There are regional differences in the MPI in the fetal myocardium whitch need to be considered searching for reference values to allow clinical use of this parameter.