Real-Time Assessment of Pulmonary Blood Flow in Pulmonary Vein Stenosis Using the Fluoroscopic Flow Calculator.

Background: Restenosis in pediatric pulmonary vein stenosis (PVS) is common and requires careful monitoring. Lung perfusion scintigraphy (LPS) is often used but involves excess radiation, is resource-intensive, and can cause patient discomfort, with no real-time data available. This study evaluated the fluoroscopic flow calculator (FFC) as a real-time tool for estimating pulmonary blood flow (Qp) using angiograms during catheterization, with the potential to replace or complement LPS. Methods: A retrospective cross-sectional study was conducted on patients with PVS who underwent cardiac catheterization between April 1, 2023, and March 31, 2024 at the Children's Hospital of Philadelphia. The study included patients who had a right ventricular angiogram and available LPS data. The FFC tool was used to analyze angiograms and estimate Qp distribution. Accuracy was assessed by comparing FFC predictions to LPS measurements using median absolute error and Bland-Altman analysis. Results: The study included 21 procedures involving 18 patients, with a median age of 17 months. The FFC tool provided accurate predictions of Qp distribution, with a median absolute error of 3%. In 76% of cases, the predicted flow split was within 5% of the LPS measurement, and all cases were within 7%. Bland-Altman analysis revealed a minimal bias of +0.3%, with no systematic bias at the extremes of the flow-split distribution. Conclusions: The FFC tool shows promise in estimating Qp distribution during cardiac catheterization in PVS patients. Further research is needed to refine the FFC method, particularly incorporating segmental lung information, and to evaluate its real-time use during catheterization.