Severe lung disease doesn’t predict worse PH in preterm infants: Study
No notable differences in blood flow found for babies with worse BPD
Having more severe bronchopulmonary dysplasia (BPD) — a chronic lung disease that occurs when a baby’s lungs aren’t fully developed — does not predict worse pulmonary hypertension (PH) in infants born preterm, according to a new study that used data from a patient registry.
The researchers found that BPD is not associated with notable differences in pulmonary blood flow — the circulation of blood from the heart to the lungs and back for oxygenation — in babies born before 37 weeks of pregnancy; a full term pregnancy is 40 weeks.
After examining data from more than 300 infants with all three grades of BPD severity, the team determined that “neither hemodynamic [blood flow dynamic] metrics nor survival were statistically different” among these patients.
“Our findings are important,” the scientists wrote, noting that the data came from “a real-world PH-focused cohort of participants from a large multicenter registry from 14 major … pediatric PH centers in North America.” Their study, the team noted, involves the “largest series of BPD-PH patients” who underwent the main diagnostic test for PH.
Titled “Pulmonary Hemodynamics and Long-Term Outcomes in Children with Pulmonary Hypertension-Associated Bronchopulmonary Dysplasia,” the study was published in The Journal of Pediatrics.
BPD primarily affects preterm infants. It can lead to related pulmonary hypertension (BPD-PH) as a result of less lung blood vessel growth and changes in the pulmonary arteries that boost pressure. The pulmonary arteries are the arteries that carry blood from the heart to the lungs.
Gold standard test for diagnosing PH considered risky for infants
Studies in this patient population typically lack detailed metrics, however. That’s because cardiac catheterization, the gold standard diagnostic test for PH, is invasive and may be risky for infants. As such, a diagnosis of PH in infants with BPD is usually made via other methods.
A recent initiative has proposed a classification of BPD severity ranging from 1 to 3 for premature infants, depending on the type of respiratory support that’s required by these babies. However, PH was not incorporated as a potential factor.
Now, to determine whether the severity of PH is associated with BPD severity, a team led by researchers in the U.S. analyzed clinical data from individuals with BPD-PH enrolled in the Pediatric Pulmonary Hypertension Network (PPHNet) registry between 2014 and 2024. The PPHNet is a multicenter study conducted at specialized pediatric PH centers across North America.
From the 1,457 children in the PPHNet registry, data from 320 were used in the analysis. The children’s average gestational age — calculated by starting from the first day of the mother’s last menstrual period — was 25.8 weeks, which falls in the extremely preterm range. The mean weight at birth of these children was 721 g (about 1.6 lbs).
Most of the children (92%) were classified as PH group 3. Although PH was usually diagnosed in infancy — at a median age of 5 months — 18% of the children were diagnosed after age 1.
Blood flow data found not to vary by BPD severity
BPD severity could be determined for 278 infants: 27% were grade 1, 44% were grade 2, and 29% were grade 3. Demographic factors and prenatal history were similar across severity groups, though the gastrointestinal issue necrotizing enterocolitis was significantly more common in infants with grade 3 BPD. Necrotizing enterocolitis is a serious condition, marked by inflammation, that mostly affects premature babies.
Regarding treatment, slightly more than half of the children received no PH-specific medications within a month of diagnosis. A total of 35% received one medication and 11% received two or more.
Nearly half of the group (144 children) underwent at least one cardiac catheterization during follow-up; 69 had catheterization within one month of PH diagnosis. This group showed evidence of precapillary PH, or high blood pressure in the blood vessels that supply the lungs. This was evidenced by high pulmonary artery pressure and increased pulmonary vascular resistance, which is a measure of the resistance that must be overcome for blood to flow through the lungs.
Twenty-five children (8%) died during the study period. Among the 22 with known BPD grade, mortality was highest in grade 3 BPD (59%). Causes of death included acute respiratory failure and progressive right heart failure.
Five-year transplant-free survival was 94% in grades 1 and 2, and 87% in grade 3, a difference that was not statistically significant, the data showed. Similarly, time to stopping PH medications or to death/lung transplant did not significantly differ by grade.
Blood flow data at diagnosis also did not vary significantly by BPD grade, though lower oxygen levels in the blood tended to occur more often in more severe BPD. Among the subgroup who underwent catheterization within one month of diagnosis, blood flow changes over time were not associated with mortality.
“In conclusion, … we found a similar distribution of grade 1, grade 2, and grade 3 BPD-PH, with a high proportion with freedom from death or lung transplant,” the scientists concluded. “Reduced survival among those with grade 3 BPD and PH may be driven by factors independent of pulmonary [blood flow] parameters.”
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