Maturational Changes in Diastolic Longitudinal Myocardial Velocity in Preterm Infants

Abstract

Background: Doppler tissue imaging (DTI) has been used to evaluate myocardial velocity during ventricular filling, a means of characterizing diastolic function. Previous studies in older children have shown age-related increases in early diastolic tissue velocities, but there are limited data in preterm infants. The aim of this study was to prospectively determine maturational changes in diastolic tissue velocities at two points in time: (1) 7 days of age and (2) 36 weeks' postmenstrual age (PMA). It was further determined whether DTI measures were altered in infants who developed bronchopulmonary dysplasia with or without pulmonary hypertension.

Methods: A total of 277 preterm infants born at <34 weeks' PMA, with birth weights between 500 and 1,250 g, were prospectively enrolled. Echocardiograms were obtained at 7 days of age and repeated at 36 weeks' PMA. Measurements included DTI assessment of early (E') and late (A') annular velocities of the left ventricular free wall, septum and the right ventricular free wall. Statistical analysis included the Wilcoxon rank sum test, simple linear regression, and the χ(2) test.

Results: At 7 days of age, there was a statistically significant increase in the E'/A' ratio as a function of gestational age at birth. At 36 weeks' PMA, E'/A' ratio was increased, but there was no association with gestational age. DTI measures were not different between infants who did or did not develop bronchopulmonary dysplasia or pulmonary hypertension at either time point.

Conclusions: A gestational age-related increase was found in the early diastolic tissue velocities of preterm infants. At a gestational age equivalent to near term, no difference was observed in diastolic tissue velocities, regardless of gestational age at birth. These findings suggest that maturational changes in diastolic function occur relatively independently of the timing of birth.

Keywords: Diastolic function; Preterm; Tissue Doppler.