SAN DIEGO — Brain development at birth is significantly delayed in full-term neonates with complex congenital heart defects, both on magnetic resonance imaging and by mean head circumference, results from a single-center study suggest.
These observations “should stimulate discussion on the optimal timing of labor induction for those infants with prenatally diagnosed heart defects,” Dr. Daniel J. Licht said at the annual meeting of the American Association for Thoracic Surgery.
“Historically, the timing of delivery for neonates with prenatally diagnosed congenital heart disease was determined by lung maturity and surgical logistics. The current study suggests that neonates with complex CHD should be delivered as close to term as possible.”
Dr. Licht, a child neurologist at Children's Hospital of Philadelphia, noted that previous studies have shown that at birth, term infants with complex congenital heart defects have smaller head circumferences and, on MRI, have been shown to have structural simplicity of the brain as seen by open operculum. Dr. Licht and his associates hypothesized that term infants with complex forms of congenital heart defects have structurally delayed brain development as measured by smaller head circumferences and a lower total maturation score (TMS), a validated MRI metric for assessing full brain maturity.
A 3-Tesla MRI was used to evaluate 29 full-term infants with hypoplastic left heart syndrome (HLHS) and 13 with transposition of the great arteries (TGA) just prior to heart surgery. Infants with evidence of perinatal distress, shock, or intrauterine growth retardation were excluded from the study “as these were felt to be independent risks for brain injury,” said Dr. Licht, who had no conflicts of interest to disclose.
Clinical studies were reviewed by a single neuroradiologist who was blinded to the clinical data and TMS were rated by two MRI readers who also were blinded to the data. The findings were compared with published normative data of similar gestational age.
The mean gestational age of the 42 infants studied was 39 weeks and 64% were boys. Their average birth weight was 3.4 kg.
The average head circumference for infants in the study was 34.5 cm, which is a full standard deviation below the expected normal of 35.5 cm. In addition, open operculum was seen on MRI in 36 of the infants (86%), and would be expected in less than 5%-10% of normal full-term infants.
The average TMS for infants in the study was just over 10, which is significantly lower than reported normative TMS of 11.1 in noncardiac infants with a gestational age of 36–37 weeks.
“This average TMS … places our term infants with congenital heart defects at 35 weeks of gestational age, a time where white matter remains vulnerable and myelination is just beginning,” Dr. Licht said. “This group of otherwise healthy term babies with congenital heart defects has immature brains as evidenced by the high prevalence of small head circumferences and open opercula and corroborated with the finding of reduced TMS scores, suggesting a delay in brain maturity of a full month.”
The study was funded by the National Institute of Neurological Disorders and Stroke and by the Dana Foundation.
Open operculum, indicating structural simplicity of the brain, was seen in 86% of neonates with congenital heart defects. Courtesy Dr. Daniel J. Licht