Changes in venous return parameters associated with univentricular Fontan circulations

Abstract

To clarify the physiology of venous return (Qvr) in Fontan circulations, venous return conductance ( Gvr) and mean circulatory filling pressure (Pmcf) were determined in pentobarbital sodium-anesthetized pigs. Relationships between Qvrand right (biventricular, n = 8) or left (Fontan, n = 8) filling pressures are described by straight lines with significant correlation coefficients. Estimated Pmcfvalues were correlated with observed Pmcfvalues in either circulations ( P ≤ 0.02). Gvrwas smaller in Fontan than in biventricular circulations (4.51 ± 0.36 vs. 7.83 ± 0.69 ml · min−1· kg−1· mmHg−1, P = 0.002) and inversely correlated with pulmonary vascular resistances in Fontan circulations ( P = 0.01). Estimated Pmcf(20.5 ± 1.4 vs. 11.1 ± 0.9 mmHg, P = 0.001) and observed Pmcf(21.8 ± 1.3 vs. 10.6 ± 0.8 mmHg, P < 0.001) were higher in Fontan versus biventricular circulations, respectively. Pulmonary artery pressure in Fontan circulations was correlated with either Pmcf( P ≤ 0.04). We conclude that in Fontan circulations 1) pulmonary vascular resistances induce a proportional decrease in Gvr; and 2) volume loading, while increasing Pmcf(similar to pulmonary artery pressure), allows the gradient for Qvrto increase and maintains systemic blood flow at a biventricular level.