Natural History of Atrial Septal Defects Diagnosed in Term Neonates

Introduction: A commonly found congenital heart disease in newborns through echocardiography is atrial septal defect (ASD) where the wall between upper chambers of the heart (atria) has a hole. The most common type of ASD is called secundum ASD based on location and etiology. ASDs can cause multiple health issues if untreated, and, as such, knowledge about their natural history is important for timely monitoring and intervention. Furthermore, with increasing use of echo in the neonatal intensive care unit, an understanding of the natural history will facilitate more appropriate triaging for pediatric cardiology follow-ups. One study of infants suggested that secundum ASDs <3mm spontaneously close whereas those ≥3mm may not. With this knowledge, all newborns with ASDs ≥3mm receive cardiology follow-up, which may lead to unnecessary resource use if they are likely to close or not require intervention. We hypothesized that the majority of secundum ASDs ≥3mm identified at <1 month age undergo spontaneous closure or significant size reduction (≤3mm, not warranting monitoring) in the first 2 years of life. Methods: To assess our hypothesis, we performed a retrospective cohort study of all term newborns (≥35 gestational age) who underwent echocardiography, were diagnosed with an ASD ≥3mm within the Royal Alexandra Hospital from 2010-2018 and had at least one repeat echo. In total, we assessed 124 patients. Results: Among all assessed patients, 58 had an ASD 3-5mm in size, 57 had an ASD 5.1-8.0mm in size, and 9 had an ASD >8mm in size on the neonatal echo. The percentage of ASDs that closed spontaneously or reduced to a size of ≤3mm within a mean period of 15 months were 93%, 89%, and 67% in each group, respectively. Out of 13 patients with persisting ASDs ≥3mm in size, 3 required ASD closure intervention, 2 of whom had an initial ASD measure >8mm. In other words, less than 2.5% of all patients with ASDs ≥3mm required ASD closure. Conclusion: Our findings confirm that the majority of neonates with ASDs experience spontaneous closure/significant size reduction and indicate that we can stop monitoring asymptomatic newborns with ASDs <8mm in size. Considering the mean follow-up period of 15 months in this study, we also recommend extending the follow-up period to 2 years for patients being monitored so that the true closure capacity of ASDs can be observed.