Improvement in pulmonary vascular resistance after relief of fontan circuit obstruction

Objectives. Patients with single-ventricle congenital heart disease undergo staged surgical palliations leading to a final Fontan procedure. After Fontan, cardiac index (CI) is primarily determined by pulmonary vascular resistance (PVR). Lower Fontan pressure has been achieved after relieving obstruction within the Fontan circuit, but to date the effect on PVR has not been quantified. We hypothesized that there would be significant reduction in PVR after relief of obstruction within the Fontan circuit; the purpose of this study is therefore to describe the change in PVR after relief of Fontan obstruction. Methods. Retrospective, single-center review of post-Fontan patients who underwent cardiac catheterization with hemodynamics, pulmonary vasodilator testing, and stenting of Fontan circuit obstructions from October 2016 to August 2019. Baseline hemodynamics were obtained on 21% fraction of inspired oxygen (FiO2), followed by administration of 80 ppm inspired nitric oxide (iNO) with repeat hemodynamics. After stenting of Fontan obstructions, hemodynamics were repeated on 21% FiO2. Patient demographics, hemodynamics, CI, and PVR were compared. Results. Twelve patients underwent stenting of Fontan circuit obstructions. There was complete relief of gradient and angiographic obstruction after stent placement in all patients. There was larger decrease in PVR after stent placement compared with iNO administration (32.1% vs 19.3%, respectively; P=.03). Conclusions. This case series provides novel data quantifying the decrease in PVR after relief of Fontan circuit obstruction, suggesting a mechanism for symptomatic improvement after intervention. These data are a compelling addition to the longterm management of this complex patient population.