OBJECTIVES: The main goal of palliative procedures for congenital heart defects is adequate pulmonary blood flow (PBF), but precise intraoperative PBF evaluation is sometimes difficult. The purpose of this preliminary study was to investigate the usefulness of velocity time integral of the pulmonary vein (PV-VTI) measured by transoesophageal echocardiography (TOE) at the time of palliative procedure as a parameter for PBF. METHODS: Case histories of 63 patients who underwent palliative procedures (bilateral pulmonary artery banding in 18 patients, main pulmonary artery banding in 22 patients and systemic-to-pulmonary artery shunt in 23 patients) and whose intraoperative PV-VTI was measured by TOE from 2011 to 2017 at our centre were retrospectively reviewed. Low-body-weight infants, cases in which cardiopulmonary bypass was used and cases that were anatomically difficult to measure were excluded. RESULTS: PV-VTIs measured at 4 orifices of the pulmonary veins were all significantly decreased in both the bilateral pulmonary artery banding and main pulmonary artery banding groups and increased in the systemic-to-pulmonary artery shunt group immediately after the procedure. There were significant correlations between the velocity time integrals of both right and left pulmonary veins and arterial oxygen saturation (r = 0.564 and 0.703). Nine patients (6 bilateral pulmonary artery banding and 3 systemic-to-pulmonary artery shunt) required unplanned early reoperation due to inadequate PBF; their PV-VTIs were significantly different from those of patients not requiring reoperation. No major complications related to TOE occurred postoperatively. CONCLUSIONS: The PV-VTI measured by TOE during palliative procedures reflected the change of PBF and could help identify patients at higher risk of early reoperation due to inadequate PBF. This parameter may be a useful additional tool for evaluating intraoperative PBF.