The clinical prognostic significance of myocardial performance index (MPI) in stable placental-mediated disease.

AIM: To determine whether a single elevated myocardial performance index (MPI) value in the third trimester of pregnancy is a marker for later adverse obstetric outcomes in stable placental-mediated disease, defined as well-controlled pre-eclampsia (PE) on a single agent and/or uncompensated intra-uterine growth restriction (IUGR).
METHODS: Fifty-five foetuses whose mothers had stable placental-mediated disease, either mild pre-eclampsia controlled on a single agent, and/or uncompensated IUGR in the third trimester, attending the Foetal Unit at Inkosi Albert Luthuli Hospital, Durban, South Africa were prospectively recruited with 55 matched controls. Recorded data for the subjects included demographic data of maternal age and parity, sonographic data of estimated foetal weight (EFW) and amniotic fluid index (AFI), myocardial performance index (MPI), and foetal Doppler data of the umbilical artery (UA), middle cerebral artery (MCA) and ductus venosus (DV).
RESULTS: The mean gestational age in the controls, the IUGR and any PE cases was 31.4, 31.8 and 31.0 weeks, respectively. The distribution of MPI values was significantly lower in the controls compared to all other groups. The highest standardised MPI values were observed in the PE-IUGR group, where a median of 5.62 was observed. The only significant differences observed between the PE and IUGR groups was the UA resistance index (p = 0.01), where the IUGR cases tended to have higher UA values compared to the combined PE group. Borderline statistical significance was observed for the MCA resistance index values ( p = 0.05) between these groups. The overall adverse event rate in the cases was 49%. The highest rate was observed in the PE + IUGR group, where eight out of 12 (67%) experienced adverse events. MPI z-scores served as a good marker of adverse events, as evidenced by the total area under the curve (AUC) of 0.90 on the ROC curve. A cut-off value of 4.5 on the MPI z-score conferred a sensitivity of 89% and specificity of 68% for an adverse event later in pregnancy. In univariate logistic regression, MPI z-score, AFI, EFW, UA Doppler, CPR category, DV Doppler and MCA Doppler were assessed separately as potential predictors of adverse outcome. The only significant predictor of adverse outcome was MPI z-score.
CONCLUSIONS: A single elevated value of the MPI ( z-score > 4.5) in the third trimester in stable placental-mediated disease was a strong indicator of adverse obstetric outcomes later in pregnancy. This has the potential to be incorporated in conjunction with standard monitoring models in stable placental-mediated disease to predict an adverse event later in pregnancy and thus to reduce perinatal morbidity and mortality.