Transcatheter Fontan Stenting: Impact on Hepatic Stiffness and Exercise Capacity

Inclusion Criteria: * Functionally single-ventricle Fontan-palliated patients undergoing clinically indicated cardiac catheterization * Anticipated Fontan stent placement for extracardiac Fontan conduit stenosis at the discretion of the primary operator * Weight ≥ 50 kg * 12-21 years of age Exclusion Criteria: * Interrupted IVC * Greater than mild atrioventricular valve regurgitation on most recent echocardiogram or MRI (RF \> 20%). * Greater than mild systemic ventricular dysfunction on most recent echo or MRI (EF \< 40%). * Non-sinus rhythm * Pacemaker * Inability to perform exercise test due to developmental or physical disability