Evaluation of Fontan-associated Hepatic Stiffness and the Efficacy of Udenafil in Reducing Liver Stiffness

This is open-label, long-term prospective study in a cohort of Fontan subjects taking drug daily for one year. The study will determine the scope of hepatic stiffness in the cohort by ultrasound and magnetic resonance imaging elastography and evaluate MZ101 pharmacotherapy as a potentially efficacious treatment to reduce liver stiffness.