Key result
Gestational-age-specific GAMLSS z-scores cut preterm elevated PVRi overdiagnosis by ~9 percentage points vs conventional cutoffs.
Why the study?
In extremely preterm infants, hemodynamic stability remains a clinical judgment rather than a measured quantity because no reference values exist for right-sided and pulmonary vascular parameters, published norms are confined to left-sided structures, and few extend below 24 weeks.
Observational (n=104)
No
This study establishes gestational-age- and birth-weight-specific biventricular echocardiographic reference values and GAMLSS z-scores for extremely preterm infants (22–29 weeks) during the first week of life, preventing bidirectional misclassification caused by fixed conventional cutoffs such as PVRi <0.25.
Answers are grounded in this paper and cite their sources.
Conventional PVRi <0.25 cutoff overflags elevated resistance in stable preterm infants; leaves open prospective validation of GAMLSS norms before adoption.
Extremely preterm infants are most at risk during the “golden hour”—delivery-room resuscitation, stabilization and transfer to the neonatal intensive care unit—whose aim is to deliver a stable infant. Yet stability remains a clinical judgment rather than a measured quantity: no reference values exist for the right-sided and pulmonary vascular parameters that define it, published norms are confined to left-sided structures, and few extend below 24 weeks. In this retrospective single-center study we established biventricular reference values and GAMLSS z-score equations from 22 + 0 weeks of gestation in 104 preterm infants who emerged from the golden hour stable and were examined on days 3–7 of life. Equations were derived for 11 of 38 echocardiographic parameters, using birth weight as the covariate for the two structural parameters and gestational age for the remaining nine; reproducibility was assessed by intraclass correlation, and sensitivity analyses were stratified by respiratory support and ductal status. Diastolic immaturity was near-universal yet gestational-age-dependent: E/A was below 1 in 94%–96% of infants born at 24 +0 –29 +6 weeks and Ar-A exceeded 0 in 100%, whereas E/A was independent of gestational age and IVRT lengthened with it ( ρ = 0.644, P < 0.001). The pulmonary vascular resistance index (PVRi; pulmonary artery acceleration time divided by right ventricular ejection time) declined with gestational age below 28 weeks ( n = 69; ρ = −0.472, P < 0.001), and applying the conventional cutoff of <0.25 would have classified 10.7% of these stable infants as having elevated pulmonary vascular resistance—26.3% of those born at 26 +0 –27 +6 weeks—whereas gestational-age-specific values flagged 1.9% overall, and infants flagged by the reference were missed by the cutoff. Only 5.8% fell below the 4.8 mm TAPSE threshold linked to death or severe morbidity, and inter-operator agreement was high for 10 of the 11 parameters; after adjustment for gestational age, neither respiratory support nor ductal status was associated with any parameter (all P > 0.08). Because conventional cutoffs misclassify in both directions, these gestational-age-specific values define what hemodynamic stability looks like in the first week, and provide a baseline for prospective validation.
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Zhou et al. (2026) conducted an observational in Hemodynamically stable extremely and very preterm infants (n=104). Gestational age and birth weight maturational assessment via GAMLSS echocardiography vs. Conventional fixed echocardiographic cutoffs (e.g., PVRi <0.25) was evaluated on Classification of elevated pulmonary vascular resistance (PVRi) using gestational-age-specific GAMLSS z-scores vs conventional cutoff (<0.25) (p=<0.001). Gestational-age-specific GAMLSS echocardiographic reference values flagged elevated PVRi in 1.9% of stable preterm infants compared to 10.7% misclassified by the conventional <0.25 cutoff.
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