Longitudinal echocardiographic parameters for evaluation of pulmonary hypertension in preterm infants with very low birth weight.

Background: Echocardiography is essential for the evaluation of pulmonary hypertension. We determined the feasible quantitative parameter for screening and monitoring pulmonary hypertension in preterm infants.

Methods: This secondary analysis of a prospective cohort single-centre study was conducted between August 2019 and September 2020. Serial echocardiography was performed 7 and 28 days after birth and at 36 weeks postmenstrual age. The data of infants who developed pulmonary hypertension at 36 weeks postmenstrual age were compared with those without pulmonary hypertension. We also modelled the parameters' trend and performed an interaction test using multi-level Gaussian regression.

Results: Out of 30 infants enrolled in the study, 79 echocardiograms were analysed. Left ventricular eccentric index was obtainable in all infants, while tricuspid jet velocity was measurable in 44.1%. Left ventricular eccentric index correlated well with tricuspid regurgitation jet velocity (r = 0.77, P < 0.001). Six infants were diagnosed with newly developed or persistent pulmonary hypertension at 36 weeks postmenstrual age. Serial left ventricular eccentric index showed a significantly different increasing trend in the pulmonary hypertension group (change per day: +0.004; P = 0.090) from the decreasing trend among a non-pulmonary hypertension group (change per day: -0.001; P = 0.041) (P for interaction = 0.007). Right ventricular systolic function and right ventricular isovolumic systolic velocity revealed a reducing trend in the pulmonary hypertension group, which was different from the improving trend in non-pulmonary hypertension infants. Infants with low current weight, low postmenstrual age, and requiring high-flow oxygen therapy at day 28 of life trended to increase the risk of late pulmonary hypertension.

Conclusion: Left ventricular eccentric index and right ventricular isovolumic systolic velocity were feasible for assessing pulmonary hypertension and should be incorporated into pulmonary hypertension evaluation. Serial left ventricular eccentric index and right ventricular isovolumic systolic velocity may help predict late pulmonary hypertension and early detection of right ventricular dysfunction.