Subdiaphragmatic venous hemodynamics in the Fontan circulation

Objective: We investigated the subdiaphragmatic venous physiology in patients subjected to the Fontan operation to understand some of the early and late problems of this circulation. Methods: Flows were evaluated by Doppler ultrasonography in the subhepatic inferior vena cava, hepatic vein, and portal vein during respiratory monitoring and with a tilt table. Twenty control subjects (group A) and 56 patients who had the Fontan operation, 27 in functional class I (group B) and 29 in class III or IV (group C), were studied. Inspiratory/expiratory flow ratio was calculated to reflect respiratory effects, and upright/supine flow ratio was calculated to assess gravity effects. Inferior vena caval, hepatic venous, and wedged hepatic venous pressures were measured during catheterization in 21 control subjects and 25 Fontan patients. The difference between wedged and hepatic venous pressures represents the transhepatic venous pressure gradient. Results: Fontan hepatic venous flow depended more on inspiration than control, but without difference between groups B and C (inspiratory/expiratory flow ratios: 1.7, 2.9, and 2.9, respectively; P