Groundbreaking cardiac surgery has significantly improved survival rates for patients with single-chamber hearts. However, despite these life-saving interventions, the long-term prognosis remains concerning, with an increased risk of heart failure, sudden cardiac death, and reduced quality of life. The absence of a chamber that pumps blood to the lungs means individuals must rely on their leg muscles to passively return blood and oxygenate the lungs. Unfortunately, studies indicate reduced muscle mass and function in these patients.

The aim is to clarify the complex interplay between single-chamber circulation and muscle function, paving the way for targeted interventions such as muscle strengthening training for this unique patient group. Our hypothesis is that muscle mass and function correlate with circulatory limitations, and that muscle strengthening training could, over time, improve both muscle and circulatory function simultaneously.

The first part of the project includes tests for maximal oxygen uptake, heart and circulatory function, muscle strength, muscle mass/body composition, and quality of life in adult patients (aged 16 and over) with single-chamber hearts.

The study may ultimately lead to improved interventions and exercise recommendations that promote an active lifestyle and enhance health, circulation, and physical function in patients with single-chamber hearts.

Inclusion Criteria:

• Diagnosis of a Fontan circulation: individuals who have undergone the Fontan procedure with only one functioning systemic ventricle, confirmed by medical records or attending physician.
• Stable clinical status: patients should be clinically stable without significant cardiovascular or renal dysfunction as determined by clinical examinations.
• Age range: 16-50 years.
• Ability to exercise: Participants must be physically able to participate in the exercise protocol according to a preliminary medical examination.

Controls: Age and sex-matched. Healthy (no chronic diseases, assessed by health questionnaire and interview).

Exclusion Criteria:

• Recent surgery or hospitalization: individuals who have undergone cardiovascular surgery or hospitalization within six months prior to inclusion.
• Severe functional limitations: Patients with clear functional limitations unrelated to Fontan physiology, such as musculoskeletal disorders.
• Significant comorbidities: Serious non-cardiac comorbidities that may independently affect work capacity, such as advanced pulmonary disease.
• Contraindications for exercise testing: Conditions that contraindicate physical testing, such as uncontrolled cardiac arrhythmias or severe heart failure (New York Heart Association III-IV).

Patients linked to the Region Stockholm outpatient clinic

The select population in the Stockholm area is too small for this. There is a clear risk that individual patients are identified.