Venous Compression in Fontan

Not Applicable

Not yet recruiting

• Conditions: Single-ventricle; Fontan Circulation

• Registration Number: NCT07220226
• Lead Sponsor: University of Texas Southwestern Medical Center

Brief Summary

The aim of this study is to investigate whether venous compression garments increase exercise stroke volume in patients with Fontan circulation. To address this aim, we will test the following hypotheses:

1. Acute and chronic external venous compression will increase exercise stroke volume in patients with Fontan circulation.

2. Patients with significant venous varicosities will have a greater response to venous compression.

Participants will:

* Undergo submaximal exercise testing in MRI to measure venous return and exercise stroke volume with and without the wearing of compression garments

* Undergo submaximal exercise testing on a seated upright exercise ergometer with concurrent measurement of stroke volume with and without the wearing of compression garments

* A subset of participants will repeat both testing visits after wearing compression garments for 2-weeks during waking hours.

Participants will:

* Undergo submaximal exercise testing in MRI to measure venous return and exercise stroke volume with and without the wearing of compression garments

* Undergo submaximal exercise testing on a seated upright exercise ergometer with concurrent measurement of stroke volume with and without the wearing of compression garments

* A subset of participants will repeat both testing visits after wearing compression garments for 2-weeks during waking hours.

Detailed Description

Study Day 1 - Consent, Screening and Garment Measurements:

Following assessment of participant eligibility, all participants will undergo leg venous ultrasound assessment and abdominal-foot measurements for the custom making of compression garments.

Study Day 2 - MRI:

Study participants will undergo comprehensive cardiovascular MRI using a 3T MRI scanner with and without compression garments and exercise.

Study Day 3 - Cardiovascular \& Exercise Testing Day:

All participants will undergo comprehensive cardiovascular structure and function assessments at rest and during exercise with and without the wearing of compression garments. Baseline testing will include dual x-ray absorptiometry (DEXA), pulmonary function testing, comprensive vascular assessments and echocardiography. During exercise at two submaximal workloads, the study team will measure blood pressure, oxygen uptake and cardiac output.

Study Timeline

• Study First Submitted: 2025-09-25
• Status Verified: 2025-10
• Study First Submitted QC: 2025-10-20
• Last Update Submitted: 2025-10-20
• Study First Posted: 2025-10-23
• Last Update Posted: 2025-10-23
• Study Start: 2025-12-01
• Primary Completion: 2027-11-01
• Study Completion: 2027-11-01

Recruitment & Eligibility

• Status: NOT_YET_RECRUITING
• Sex: All
• Target Recruitment: 20

Inclusion Criteria

Not provided

Exclusion Criteria

• NYHA Class 4
• Severe AV valve regurgitation
• Severe ventricular dysfunction
• Large ascites
• Significant varicosities
• Atrio-pulmonary (AP) Fontan
• Known Fontan thrombus
• Poorly controlled arrythmia
• Unplanned cardiac admission in the last 6 months
• Cyanosis (resting O2 saturation <85%)
• Pregnant
• Common femoral vein obstruction >50% to be performed following completion of informed consent.

Healthy Controls:

Healthy control participants will be recruited on the basis of having no known chronic diseases and not currently taking any cardiovascular medications.

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: SEQUENTIAL

Primary Outcome Measures

Name	Time	Method
Change in Stroke Volume with Exercise	Rest (20 mins), Exercise (10 mins) at 2-weeks follow-up testing	The change in single ventricular stroke volume from rest to moderate intensity exercise following 2 weeks of wearing compression garments.
The Acute Effect of Compression Garments on Stroke Volume during Exercise	Rest (20 mins) and Exercise (10 mins) repeated during baseline testing	The difference in the change in single ventricular stroke volume during moderate intensity exercise between baseline testing with (outcome #1) and without (outcome #2) garments
The Chronic Effect of Compression Garments on Stroke Volume during exercise	Rest (20 mins) and Exercise (10 mins) completed during baseline and during follow-up testing	The difference in the change in single ventricular stroke volume during moderate intensity exercise between baseline testing without garments (outcome #2) and following 2 weeks of wearing compression garments (outcome #3) in patients with Fontan Circulation.

Secondary Outcome Measures

Name	Time	Method
Change in Venous Return with Exercise	Rest (10 mins) and Exercise (5 mins)	The change in inferior vena cava flow from rest to moderate intensity exercise following 2 weeks of wearing compression garments using MRI
The Acute Effect of Compression Garments on Changes in Venous Return with Exercise	Rest (10 mins) and Exercise (5 mins) repeated during baseline testing	The difference in the change in inferior vena cava flow during moderate intensity exercise between baseline testing with (outcome #6) and without (outcome #7) garments
The Chronic Effect of Compression Garments on Changes in Venous Return with Exercise	Rest (10 mins) and Exercise (5 mins) completed during baseline and during follow-up testing	The difference in the change in inferior vena cava flow during moderate intensity exercise between baseline testing without garments (outcome #7) and following 2 weeks of wearing compression garments (outcome #8) in patients with Fontan Circulation.