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).

Inclusion Criteria:

• Individuals born with pulmonary atresia with intact ventricular septum (PA-IVS) who are 15 years or older at the start of the study.
• Regarding the mortality variable, research subjects who have died after the age of 15 years old will be included.

Exclusion Criteria:

Individuals born with pulmonary atresia with intact ventricular septum who are younger than 15 years old at the start of the study.

The study population consists of all individuals with PA-IVS who have been registered in Swedcon (a national register for patients with congenital heart defects) or in the National Patient Register and Cause of Death Register since 1980 and meet other inclusion criteria, including age.