Univentricular heart (UVH) is a severe congenital heart disease. Accurate advanced non-invasive diagnostic methods is limited. Cardiovascular magnetic resonance (CMR) imaging has evolved as a particularly useful tool for the study of patients with adult congenital heart disease (ACHD) considering its ability to determine detailed anatomy and detect early cardiac dysfunction without the need for radiation exposure. Most of contemporary treatment recommendations are based on consensus opinions/documents and small studies from local, or national registries. Improved knowledge is needed in all these areas to facilitate clinical decisions regarding treatment, monitoring and follow-up. This study seeks to answer if early detection of deterioration in cardiac function, venous pressure and microvascular dysfunction can identify patients before the symptoms progress and thus help to initiate early treatment. The hypothesis is that quantitative myocardial stress-perfusion maps improves the pathophysiological insight in patients with UVH. The overall goal with this research proposal is to implement combined advanced CMR imaging for a comprehensive non-invasive mapping of functional cardiovascular behavior in patients with complex UVH disease. The outcome of this research may benefit this young adult patient population due to early detection of cardiac disease, less hospitalizations because of heart failure, and eventually decrease morbidity and mortality.