Muscle Function in Patients With Single-chamber Heart (Muscle in TCPC)

Importance of Muscle Function for Patients With Single-chamber Heart

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.

Study Overview

• Status: Not yet recruiting
• Conditions: Fontan Circulation

• Study Type: Observational
• Enrollment (Estimated): 40

Contacts and Locations

• Study Contact: Name: Andrea Tryfonos, PhD; Email: andrea.tryfonos@ki.se
• Study Contact Backup: Name: Tommy Lundberg, PhD; Phone Number: +46738352974; Email: tommy.lundberg@ki.se

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Patients linked to the Region Stockholm outpatient clinic

Description

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).

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort
Controls
Patients

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Relationship between anterior thigh muscle volume and peak maximal oxygen uptake in patients vs. controls	Muscle volume is measured in litres using magnetic resonance imaging. VO2peak is measured in L/min and ml/kg/min using cardiopulmonary exercise testing with breath-by-breath gas analyzers.	Baseline visit (single time-point)
Relationship between knee extension muscle strength and peak maximal oxygen uptake in patients vs. controls	Muscle strength (isometric peak torque) is measured in Nm using Biodex. VO2peak is measured in L/min and ml/kg/min using cardiopulmonary exercise testing with breath-by-breath gas analyzers.	Baseline visit (single time-point)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Anterior thigh muscle fat infiltration in patients vs. controls	Measured in % using magnetic resonance imaging.	Baseline visit (single time-point).
Whole body muscle composition in patients vs. controls	Measured in L and/or per kg body mass using magnetic resonance imaging	Baseline visit (single time-point)
Quality of life in patients vs. controls and its relationship to muscle function	Quality of life aspects are measured using surveys (SF-36).	Baseline visit (single time-point visit)
Cardiac function in patients vs. controls	Ventricular end-diastolic volume, Ventricular end-systolic volume, and Stroke volume measured in ml/m²	Baseline visit (single time-point)
Whole body fat composition in patients vs. controls	Measured in L and/or per kg body mass using magnetic resonance imaging	Baseline visit (single time-point)

Collaborators and Investigators

• Sponsor: Karolinska Institutet

Study record dates

Study Major Dates

• Study Start (Estimated): February 18, 2026
• Primary Completion (Estimated): May 31, 2026
• Study Completion (Estimated): May 31, 2026

Study Registration Dates

• First Submitted: January 28, 2026
• First Submitted That Met QC Criteria: February 11, 2026
• First Posted (Actual): February 19, 2026

Study Record Updates

• Last Update Posted (Actual): February 19, 2026
• Last Update Submitted That Met QC Criteria: February 11, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Skeletal muscle; Congenital heart disease; muscle function; Fontan patients
• Additional Relevant MeSH Terms: Cardiovascular Diseases; Heart Diseases; Congenital Abnormalities; Cardiovascular Abnormalities; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Heart Defects, Congenital
• Other Study ID Numbers: 2024-07444-01

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: The select population in the Stockholm area is too small for this. There is a clear risk that individual patients are identified.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No