Can a volume challenge pinpoint the limiting factor in a Fontan circulation?

Abstract

Objective It is diffi cult to indicate whether the limitation in a failing Fontan circulation lies within the pulmonary vasculature or the heart. Such diff erentiation is crucial to direct adequate therapy. This study was set out to determine if a volume challenge could identify the limiting factor.Methods and study population Thirty-two catheterizations in 28 patients with a Fontan circulation were included. Pressures and oxygen saturations were measured before and after volume challenge (NaCl 0.9%; 15 cc/Kg). The changes in data were grouped based on the location of the major pressure increase. Ventricular function was measured in the resting state.Results The majority of the patients showed an increase in aortic oxygen saturation, mixed venous oxygen saturation, systolic, pulmonary and systemic venous pressures. The arterio-venous oxygen gradient decreased, suggesting an increase in cardiac output. Diff erent patterns in pressure changes were observed. Most (n = 17) showed a similar increase of ventricular end-diastolic pressure and mean venous pressure (MVP); some (n = 7) showed a lower increase of MVP, suggesting pulmonary reserve and recruitment; others (n = 8) showed a signifi cant higher increase in MVP, suggesting increased pulmonary vascular resistance. All volume challenge was well tolerated.Conclusion Most patients were preload-responsive. The pressure changes following volume load showed patterns with a potential of diff erentiating between patients with a major pulmonary or cardiac limiting factor.