Myocardial performance index (Tei index) in term and preterm neonates during the neonatal period

Background: The myocardial performance index (MPI) is a noninvasive method to measure global systolic and diastolic myocardial function. In both term and premature neonates, changes in the systolic and diastolic function of the left ventricle (LV) and right ventricle (RV) reflect the degree of neonatal myocardial immaturity and the co-existence of foetal circulation. Aim: To assess MPI (or Tei indices) of both ventricles in term and preterm newborns, and to observe MPI trends throughout the neonatal period. Methods: Heart ultrasound imaging was performed on the first day of life (DOL), after patent ductus arteriosus (PDA) closure, and on the 28th DOL, in 29 term and 29 preterm newborns. RVMPI and LVMPI were measured within the preterm group at 40 weeks of post-conception age (PCA). Results: A statistically significant reduction in RVMPI was observed in both term and preterm newborns. In term newborns, the RVMPI value on the first DOL was 0.42 +/- 14, dropping to 0.29 +/- 0.09 after PDA closure, and finally reaching 0.22 +/- 0.09 on the 28th DOL. The respective RVMPI values for the preterm newborns were 0.44 +/- 0.15, 0.30 +/- 0.12, and 0.21 +/- 0.08. Little variability in the mean values of LVMPI was observed in both groups throughout the neonatal period. The LVMPI for term neonates in successive measurements was 0.37 +/- 0.10, 0.39 +/- 0.07, and 0.37 +/- 0.11, respectively, and for the preterm neonates it was 0.37 +/- 0.10, 0.35 +/- 0.09, and 0.36 +/- 0.10, respectively. The MPI values from preterm newborns taken at 40 weeks PCA (RVMPI = 0.28 +/- 0.09; LVMPI = 0.37 +/- 0.05) were comparable to those measured in term newborns after PDA closure. Conclusions: Observed postnatal changes in RVMPI correspond to changes in ventricular function, reflecting the haemodynamic changes of the transitional circulation. The relatively small postnatal changes in LVMPI in term and preterm newborns may reflect an immature myocardium. The RVMPI and LVMPI values at 40 weeks PCA in preterm newborns correlate best with MPI values in term newborns just after PDA closure.