Pathophysiology of chronic venous insufficiency in adults with a Fontan circulation (a pre-defined substudy of the CALF investigation)

Objectives To investigate the pathophysiology of chronic venous insufficiency in adults with a Fontan circulation. Background Chronic venous insufficiency (CVI) is prevalent in adults with a Fontan circulation, however the underlying pathophysiology has not been identified. We defined the prevalence of venous reflux and obstruction in a Fontan population, identified associated factors, and assessed the hypothesis that venous reflux correlates with clinical CVI in adults with a Fontan circulation. Methods Fifty-one adult Fontan subjects from the Congenital Heart Disease in Adults: Lower Extremity Systemic Venous Health in Fontan Patients (CALF) study, ten control subjects without cardiac disease, and ten comparator subjects with repaired tetralogy of Fallot underwent lower extremity Doppler venous ultrasound. We investigated 10 venous segments in each subject for venous obstruction and reflux. Results The prevalence of venous reflux was significantly greater in the Fontan population compared to healthy controls (51% vs. 10%, p=0.03). Venous flow patterns demonstrated a range of pulsatility and biphasic flow in many subjects. There was no evidence of venous obstruction in any subject. Venous reflux did not correlate with clinical venous insufficiency; 49% of Fontan subjects with observed venous reflux demonstrated no clinical signs of venous disease. Predictors of venous reflux in multivariate analysis were single right ventricle (p=0.03), use of anti-arrhythmic medications (p=0.04), and family history of venous disease (p=0.003). Conclusions Venous reflux is highly prevalent and venous obstruction is absent in adults with a Fontan circulation. Clinical CVI underestimates pathophysiologic venous insufficiency in adults with a Fontan circulation.