Doppler-derived parameters of diastolic left ventricular function in preterm infants with a birth weight <1500 g: reference values and differences to term infants.

Transmitral flow parameters in preterm and term infants were compared in order to study differences in signal expression and temporal dynamics of left ventricular diastolic function. In 63 preterm infants between 26 and 33 weeks of gestation and 102 term infants, a Doppler survey was performed during 6 months after birth. Early and atrial filling-time velocity integrals and peak velocities were significantly lower in the preterm neonates. Atrial filling parameters reached the level observed in term infants by 2 months of age. Peak early filling velocity was still lower for 2-month-old preterms and attained the term infants' level by 3 months of age. Preterm infants continued having high atrial filling fraction (AFF) (0.51+/-0.07) during 2 months after birth, while in term infants the fraction decreased continuously from 0.41+/-0.06 to 0.37+/-0.05. Isovolumic relaxation time (IVRT) was the only parameter without differences between preterm and term infants, and it decreased from 54+/-7 ms in neonates to 41+/-4 ms over 3 months. Stroke volume passing the mitral valve doubled in preterm (4+/-1 to 7.9+/-1.5 ml/cm2), but increased by only 37% (6.9+/-1.6 to 9.5+/-2.2 ml/cm2) in term infants. Our observations show that the maturational period of diastolic function appears prolonged in preterm infants. As preterm infants have to cope with a higher physiologic preload augmentation during growth, part of the delay in parameter changes might be caused by preload stress rather than by persistence of functional impairment. Although doing well under physiological conditions, preterm neonates may be at higher risk for diastolic dysfunction than term infants when an additional preload challenge is encountered.