We hypothesized that mean pulmonary artery pressure (PAP) detected on a pulmonary flow study may predict medium-term survival and right ventricular systolic pressure (RVSP) in patients with pulmonary atresia (PA), ventricular septal defect (VSD), and major aortopulmonary collateral arteries (MAPCAs).Fifty patients with PA/VSD/MAPCAs underwent unifocalization between 2000 and 2013, and 40 of these patients had a pulmonary flow study since 2003. Predictability of the mean PAP on VSD status, medium-term survival, reintervention, and RVSP were analyzed.Forty-seven of the 50 patients (94%) had complete unifocalization at a median age of 11 months (range, 1-194 months), and 37 patients (74%) achieved VSD closure. Among the 40 patients who underwent a pulmonary flow study, the VSD was closed in 34 (85%), with salvage VSD fenestration in 4 (10%), and was intentionally left open in 6 (15%). Survival was 85.5% at 1 year and 78.5% at 5 years. A mean PAP ≥25 mm Hg was associated with worse survival (P = .011). Cox regression analysis identified a mean PAP ≥25 mm Hg as the sole predictor for death (P = .037). Patients with an open VSD had an increased risk of reoperation (P = .001) and pulmonary artery reintervention (P = .010), and had a trend toward increased risk of death (P = .059), compared with those with a closed VSD.PAP obtained from the intraoperative pulmonary flow study is associated with medium-term survival and late RVSP in patients with PA/VSD/MAPCAs. VSD closure for patients with a mean PAP ≥25 mm Hg on a flow study is considered high risk, and sensible judgment and a low threshold for VSD fenestration are required.