Prospective longitudinal assessment of the fetal left modified Myocardial Performance Index

Introduction: The fetal left modified Myocardial Performance Index (Mod-myocardial performance index (MPI)) is a measure of systolic versus diastolic time intervals obtained from a single cardiac cycle with ultrasound. It is a measure of global ventricular function and has been investigated for potential utility in fetal conditions associated with cardiac dysfunction.Objectives: The objective of this study is to compare values from a precisely replicated fetal left Mod-MPI technique to published reference ranges.Methods: Three hundred and sixty-five nulliparae prospectively underwent fetal left Mod-MPI measurement at 27+0–29+0 and 35+0–37+0 weeks’ gestation. Measurements from pregnancies complicated by gestational diabetes mellitus, preeclampsia, or a small-for-gestational-age (<10th centile) infant were excluded. Mod-MPI values were compared with three published references created using similar measurement techniques.Results: Compared with one selected reference, at 29+0 and 35+0–37+0 weeks’ gestation, 90–100% of our values fell within the 5th–95th percentile range as expected. Thus, this reference range was validated for our population in late pregnancy. However, the expected level of concordance was not seen at 27+0–28+6 weeks’. The other two references to which we compared our Mod-MPI values demonstrated poor concordance, especially at 27+0–29+0 weeks’. Pearson interobserver correlation was also improved at 35+0–37+0 weeks’ at 0.434, compared with 0.083 at 27+0–29+0 weeks’ gestation.Conclusions: Concordance and interobserver variability between our cohort and similar populations were both improved at 35+0–37+0 weeks’ compared with 27+0–29+0 weeks’ gestation. Overall, variable Mod-MPI reproducibility across gestations limits clinical application, especially earlier in pregnancy. Manual Mod-MPI measurement should be considered most reliable in late pregnancy until automated MPI measurement is possible.