Feasibility of automated measurement of fetal right ventricular modified myocardial performance index with development of reference values and clinical application

To establish normal reference ranges for fetal right ventricular modified myocardial performance index (RV Mod-MPI) using automatic synchronization of the RV inflow and outflow images (MPI^+TM). Additionally, we aimed to clinically apply RV Mod-MPI to investigate its changes in fetal right congenital diaphragmatic hernia (CDH) compared to normal fetuses. This prospective study included uncomplicated singleton pregnancies between 16 and 38 weeks of gestational age. Cases with any maternal or fetal complications that developed during the enrollment period were excluded. Two experienced operators measured the RV Mod-MPI using the automated and manual methods. The intraclass correlation coefficients (ICC) were calculated for intra- and inter-operator reproducibility. The mean differences between the manual and automated measurements were also compared. The RV Mod-MPI was then compared between the right CDH fetuses and normal fetuses. Seventy normal fetuses were analyzed for the feasibility of an automated system, and 364 examinations from 272 fetuses were analyzed for developing the normal references. The automated system showed significantly higher intra- and inter-operator reproducibility of Mod-MPI than those of manual measurements (ICC = 0.962 vs. 0.913 and 0.961 vs. 0.889, respectively). The mean difference in Mod-MPI between the manual and automated method was 0.0002 ± 0.0586 with a 95% confidence interval of -0.0095-0.0099. The Mod-MPI and isovolumetric relaxation time increased throughout the gestational weeks. The isovolumetric contraction time increased until 24 weeks of gestation and then slightly decreased afterwards, and the ejection time also increased until 31 weeks of gestation and then decreased. There was no significant difference in the Mod-MPI between right CDH and normal fetuses. The automated system showed high inter- and intra-operator reproducibility. Furthermore, the normal reference values of Mod-MPI for each gestational age were established. Our results suggest that the automated system might be clinically feasible for evaluating fetal cardiac function.