Abstract Body (Do not enter title and authors here): Deferral of the Stage 1 Norwood Palliation (S1P) for infants with hypoplastic left heart syndrome and other high-risk features is sometimes accomplished using a hybrid approach involving external pulmonary artery (PA) banding. Recently, percutaneous restriction of pulmonary blood flow has been accomplished with off-label modification of microvascular plugs (Medtronic) to delay surgical intervention.

This single-center, retrospective case series examines outcomes associated with PA flow restrictors in patients at both high and standard-risk for S1P. High-risk criteria included prematurity, birth weight less than 2.5 kg, moderate or greater atrioventricular valve regurgitation, highly restrictive atrial septum, and genetic comorbidities. Primary outcomes included death, need for extracorporeal membrane oxygenation (ECMO), PA re-intervention, and variation from expected pathway post bidirectional Glenn (BDG), which includes prolonged intubation (>24 hours), persistent hypoxia (saturation <75%), or prolonged hospital length of stay (>14 days).

From September 2023 to May 2024, bilateral PA flow restrictors were placed in 9 S1P-eligible neonates (Table 1). Two patients died with flow restrictors before S1P. One patient developed progressive heart failure and underwent a successful heart transplant after having PA flow restrictors in place for 200 days. The remaining 6 patients had a S1P operation with removal of flow restrictors and PA plasty at a median of 21 days post insertion and 25 days of life. Three patients required PA stents between S1P and BDG. Four patients have progressed to Glenn, all of whom had courses that significantly varied from the expected pathway, including 2 who required early PA stenting, 4 who had prolonged hospital stays, and 1 patient who died of multiorgan failure due to failed BDG circulation.

Flow restrictors can delay surgical S1P in high-risk patients, allowing for evaluation of additional comorbidities. They are a useful adjunct to the management of high-risk patients prior to S1P. However, their use appears to be associated with an important rate of PA complications, resulting in significant variation from the expected clinical course and may impact later quality of BDG circulation.