Cardiac Magnetic Resonance Stress-perfusion Study in Patinets with Fontan Circulation

"Included patients will be examined at the Karolinska University Hospital in a 1.5T Siemens Sola magnetic resonance camera at rest and during adenosine stress with specific CMR sequences (adenosine stress-perfusion, myocardial velocities, and tissue characterization) for non-invasive determination of macro- and microvascular dysfunction, global myocardial function, pulmonary artery pressure and scarring of the myocardium.~Adenosine or Regadenoson will be used as stress medication which is according to clinical routine. Adenosine will be infused over approximately 5 minutes (110-140 μg / kg/min), Regadenoson (5 ml) will be a 10-second injection (400 μg single dosage). Intravenous gadolinium-based contrast agents will be administered, Gadovist (1 mmol/ml, gadobuterol), 0.15 mmol/kg during stress and rest."