The purpose of this study is to evaluate causes and risk factors for liver disease in those whom have 1) undergone the Fontan procedure or 2) whom have dilated cardiomyopathy.

Participants in this study will have a blood sample collected, undergo cardiac magnetic resonance imaging (CMR), a liver magnetic resonance imaging (MRI), shear wave ultrasound elastography (SWE), echocardiography, liver Doppler ultrasound, and an exercise stress test. Participants medical records will be reviewed to collect information on previous medical procedures. Participation is complete once all imaging studies and blood sample have been collected.

This is not a treatment study; if one chooses not to participate, s/he will continue to undergo regularly scheduled clinical procedures.

The goals of this study are to understand the mechanisms behind the development of heart failure in children born with complicated heart defects consisting of a functional single pumping chamber, improve the ability to objectively measure cardiac function in these patients and determine the relationship of these pathophysiologic mechanisms to outcomes.