Dextro-transposition of great arteries (dTGA) accounts for 5-7% of all congenital heart disease. For neonates born with dTGA and an intact ventricular septum (dTGA/IVS), hypoxia and hemodynamic compromise present serious risks at birth. But prenatally identifying which patients will develop hypoxia and need urgent treatment with balloon atrial septostomy (BAS) remains a challenge.
Christopher Lindblade, MD, medical director of the Phoenix Children’s Fetal Cardiology Program was one of 30 co-authors on a paper from the Fetal Heart Society Research Collaborative to examine whether fetal echocardiogram findings could detect any anatomic or physiologic factors that may predict neonatal hypoxia in this patient group. While their research didn’t reveal any new markers, it does offer guidance for delivery planning.
“This study did not identify any sensitive prenatal predictors of neonatal hypoxia with prenatal diagnosis of transposition of the great arteries with intact ventricular septum,” he said. “Therefore, high-risk delivery planning for the possibility of neonatal hypoxia and urgent balloon atrial septostomy is warranted for all infants with dTGA.”
The Diagnostic and Treatment Problem
Children born with dTGA/IVS face a life-threatening cycle of improperly circulated oxygenated and deoxygenated blood. Timely treatment with BAS shortly after birth is necessary to correct that systemic oxygenation, reduce mortality and mechanical ventilation, and help bridge these newborns to arterial switch surgery.
Identifying – before birth – whether a neonate will need BAS may improve their outcomes. To date, existing research has examined whether various prenatal predictors, such as hypermobility of the atrial septum and diastolic flow reversal in the ductus arteriosus or the size of foramen ovale to total septal length ratio, could reveal which babies will need treatment. None have been reliable.
A 2024 research study led by Christopher Lindblade, MD spotlighted that putting a BAS intervention team at the delivery bedside can accelerate how quickly babies receive BAS after birth. Those results, based on data collection that began in 2018, spurred Dr. Lindblade’s team to explore whether fetal echocardiography could provide more answers.
Examining Prenatal Factors for Clues
To identify any predictive factors, Dr. Lindblade and his colleagues designed a prospective, observational multicenter study. To date, it’s the largest of its kind to search for any anatomic predictors of neonatal hypoxia.
Between 2019 and 2022, the team enrolled 132 mother-infant pairs with a dTGA/IVS diagnosis from 23 North American institutions. By examining third trimester fetal echocardiograms, called acute maternal hyperoxygenation (MHO) testing, they gathered multiple fetal cardiac measurements, including:
- Foramen ovale to total septal length ratio (primary indicator due to previous sensitivity)
- Septum primum angle
- Atrial septal excursion ratio
- Hypermobility of the atrial septum
Based on these measurements, they defined two outcomes. First, they determined the lowest arterial partial pressure of oxygen (PaO2) (or pulse oximetry — SpO2) before BAS or cardiac surgery after the first five minutes of life. They defined neonatal hypoxia as PaO2 less than 30 mmHg or SpO2 less than 75%. Secondary outcomes focused on whether a pediatric interventional cardiologist performed BAS, the urgency of the procedure and any perinatal mortality.
According to their analysis, 38% of infants developed neonatal hypoxia. Roughly 61% of them underwent BAS with nearly 88% of the procedures considered urgent. However, 51% of babies without hypoxia also had BAS with 88% considered urgent. As a result, Dr. Lindblade said, this evaluation of measurements offered no new insights into predictors of neonatal preoperative hypoxia.
“Importantly, no fetal echocardiographic finding could reliably identify which infants would remain stable after birth,” he said. “Fetal echocardiographic findings both missed and overcalled the need for atrial septostomy and urgent care at delivery.”
A Case for Better Delivery Planning
While the study results didn’t reveal any new predictive factors, they do point to the need for better high-risk delivery planning for all babies diagnosed with dTGA/IVS before birth, Dr. Lindblade said. Providers should make extra preparations even if they suspect a lower risk of neonatal hypoxia.
“The major clinical message is that every infant with prenatally diagnosed dTGA/IVS should have delivery planning that anticipates the possibility of significant hypoxemia and the need for urgent BAS,” he said. “This is true even when the fetal echocardiogram appears reassuring.”
Knowing the importance of this additional level of planning can potentially improve neonatal outcomes. For example, hospitals without 24-hour access to pediatric cardiologists or BAS resources can plan ahead to have that coverage available during delivery. Prior to delivery, other, more remote locations may also choose to transfer the pregnant patient to a tertiary care center where neonatal cardiac interventional and surgical services are readily available.
Validation of the Phoenix Children’s Model
Dr. Lindblade said the results of this study also reinforce the effectiveness of the model of care Phoenix Children’s launched in 2018 for babies with dTGA/IVS. This approach, detailed in Dr. Mattia’s above-mentioned 2024 study published in Pediatric Cardiology, places an interventional cardiology team and a sonographer at the bedside during every delivery of a neonate with dTGA.
This study compared time-to-procedure outcomes for 112 patients with dTGA across three different patient groups: postnatal diagnosis, prenatal diagnosis with rapid transport and prenatal diagnosis with a bedside interventional team performing BAS at delivery. According to data analysis, having an interventional group on hand substantially reduced the time between birth and BAS.
The time-to-treatment for the interventional group was 1.1 hours compared to 9.3 hours for postnatal diagnosis patients and 4.5 hours for the rapid transport group. Although the shorter timeframe didn’t reduce the hospital stay for the interventional group, these patients did experience lower peak lactate levels and less severe acidemia.
“These results are fantastic and should provide reassurance to our families in Arizona that they’re receiving the highest level of coordinated care when their child with a prenatal diagnosis of dTGA delivers in Phoenix,” Dr. Lindblade said.
This Phoenix Children’s model, formalized in 2025, can serve as an example to other facilities committed to multidisciplinary collaborations that can improve care for this vulnerable patient population.
Refer a Patient or Request a Consult
The Fetal Cardiology Program at Phoenix Children’s delivers comprehensive diagnostic and management care for patients with complex fetal cardiovascular disorders. To refer a patient or request a consultation, call 602-933-KIDS (5437) or submit a referral online.
About the Author
Christopher Lindblade, MD
Medical Director, Fetal Cardiology Program at Phoenix Children’s
Dr. Lindblade completed his pediatric internship and residency training at the University of Texas McGovern Medical School in Houston. He also completed a pediatric cardiology fellowship at Indiana University School of Medicine. He is board certified in general pediatrics and pediatric cardiology and is committed to advancing the field of pediatric cardiovascular research.
Source
Johnson Joyce T, Schidlow David, Shuplock Jacqueline, et al. Fetal Anatomic and Physiologic Predictors of Neonatal Hypoxia in D-Transposition of the Great Arteries: A Prospective Multicenter Study by the Fetal Heart Society Research Collaborative. Journal of the American Society of Echocardiography 2026 July. doi: 10.1016/j.echo.2026.07.010 https://onlinejase.com/article/S0894-7317(26)00366-4/abstract.
Mattia Donald, Christopher Lindblade, Coronado Claire, Garn Byron, et al. Prenatal Detection of D-TGA and Novel Interventional Program Decrease Time to Balloon Septostomy. Pediatric Cardiology 2024 May. doi: 10.1007/s00246-024-03679-3. https://pubmed.ncbi.nlm.nih.gov/39384586/.
