Outcomes of Fetuses with Mild Aortic Stenosis: A Multicenter Study.

Background: Severe fetal aortic stenosis (AS) has been studied extensively; however, outcomes of fetuses with mild AS are unknown. With improvements in fetal imaging, more of these patients will be identified. This is the first retrospective cohort study evaluating outcomes in mild AS on initial fetal echocardiogram.

Methods: Patients with an initial fetal echocardiogram at four centers between January 2009 to January 2019 with mild AS (peak aortic valve velocity > 1 m/sec, antegrade aortic arch flow, and mild or no left ventricular [LV] systolic dysfunction) were included. Fetuses with worse than mild LV hypoplasia or other heart defects were excluded. Data were collected from the initial and final fetal echocardiogram, initial postnatal echocardiogram, and the echocardiogram prior to either the first aortic valve intervention or at one year of life. The primary outcome was aortic valve intervention at one year. Investigators compared echocardiographic measures for those who did and did not undergo intervention using the Wilcoxon rank-sum test.

Results: At the 4 participating centers over 10 years, there were 22 patients, with a median gestational age of 24.7 weeks (22.9, 27.3). Eight patients (36.4%) underwent a postnatal aortic valve intervention within the first year of life. Among these, 4 (50%) were considered to have critical (ductal-dependent) AS. There was a significant difference in aortic valve peak gradient (PG) between those who did and did not require an intervention on the initial fetal echocardiogram (p 0.0017) and the final fetal echocardiogram (p 0.0016). All patients with an aortic valve PG > 12.5 mmHg on the initial fetal echocardiogram underwent intervention during the first year of life. Patients who underwent intervention also had a lower sphericity index on the initial fetal echocardiogram than those who did not (p 0.045).

Conclusion: Mild fetal AS is uncommon and has variable outcomes. Approximately one third of our cohort underwent aortic valve intervention by one year of life. Aortic valve PG and LV sphericity index, a relatively novel marker, appear useful in identifying fetal patients that may require intervention during infancy.