The goal of this observational study is to compare patients with pulmonary atresia with intact ventricular septum (PA-IVS) with univentricular circulation to patients with the same heart defect but that has a biventricular circulation in regards to mortality, quality of life, comorbidity, cardiac function, and work capacity. The main questions the study aims to answer are: • Do mortality, quality of life, comorbidity, cardiac function, and work capacity differ between patients with PA-IVS who have univentricular and biventricular circulation? Participants will be asked to answer a Quality of Life questionnaire. The investigators will also inquire with a sample size of the research subjects (based on place of residence) about their participation in a series of examinations (ergo-spirometry to assess work capacity, transthoracic echocardiogram, magnetic resonance of the heart and blood sampling to assess cardiac function and cardiac health).