Fetal left ventricular myocardial performance index: Defining normal values for Indian population and a review of literature

Objective : The aim of this study was to determine normal values for fetal left ventricular (LV)-myocardial performance index (MPI) in Indian population and to assess its relation to advancing gestation and fetal heart rate (FHR). Materials and Methods : Two hundred pregnant women without any pregnancy-related complications and whose fetuses were shown to have structurally normal hearts were enrolled in this study. Doppler waveform involving simultaneous display of mitral inflow and LV outflow was obtained in all. Various intervals including isovolumetric contraction time (IVCT), isovolumetric relaxation time (IVRT), and ejection time (ET) were measured and then the MPI was calculated using the formula IVCT + IVRT/ET. Also the correlation between MPI and gestation age and FHR was assessed. We also reviewed the literature on the use of MPI for the assessment of fetal LV function. Results : The normal MPI in second and third trimester fetuses of Indian population was 0.42 +/- 0.03. The mean IVCT was 33 +/- 4 milliseconds (ms), mean IVRT was 39 +/- 5 ms, and mean ET was 169 +/- 9 ms. The mean heart rate was 148 +/- 8 bpm and the mean PR interval was 111 +/- 10 ms. There was no significant association of LV-MPI with either FHR or advancing gestation. Conclusion : MPI is a useful parameter for the assessment global cardiac function. MPI has the advantage of not being affected by FHR, ventricular size, and geometry or image quality. The review of literature shows its significant importance in monitoring complicated pregnancies.