The Cardiovascular Effects of Patent Foramen Ovale in Hypoxia

NCT07742540 | Not Yet Recruiting

• 2 other identifiers: STU-2026-1373Herbert N. Hultgren Grant
• Study Type: observational
• Target: 50
• Locations: 0 countries
• Sites: N/A

Brief Summary

Before birth, the foramen ovale is a normal opening in the heart that allows blood to flow from the mother to the baby. After birth, this opening usually closes. However, in up to 38% of the population it does not fully close and is then called a patent foramen ovale (PFO). Having a PFO allows venous (blue) blood to mix with arterial (red) blood in the heart, which can lower blood oxygen levels. The mixing of blood has been suggested to be greater during exercise and with exposure to high-altitude. Also, people with a PFO may be a greater risk for severe altitude sickness, specifically involving the collection of fluid in the lungs which makes breathing very difficult - this is called high-altitude pulmonary edema (HAPE). No study has directly measured the pressure difference across the heart which is required for the mixing of blood during exercise or at high-altitude. The present study will directly measure the pressure difference across the heart, as well as blood flow through the PFO during rest and exercise in simulated high altitude in adults with and without a PFO and a previous history of severe altitude sickness. The study will test the hypothesis that elevations in pulmonary artery pressure during exposure to hypoxia will not elicit a pressure gradient, and thus blood flow, across the PFO neither at rest nor during exercise.

Conditions

Patent Foramen Ovale (PFO); High Altitude Pulmonary Edema

Keywords

hypoxia; altitude; heart; high altitude pulmonary edema; patent foramen ovale; exercise; pulmonary artery pressure; intracardiac pressures; right-to-left shunt

Outcome Measures

Primary Outcomes (3)

• Transmural pressure

  Absolute difference between pulmonary capillary wedge pressure and right atrial pressure

  During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.

• Arterial oxygen saturation

  During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.

• Pulse oxygen saturation

  During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.

Secondary Outcomes (6)

• Gas exchange

  During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.

• Arterio-venous oxygen different

  During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.

• Cardiac output

  During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.

• Right ventricular diameter

  During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.

• Tricuspid regurgitant jet velocity

  During 5 minutes of rest in normoxia, after 15 minutes of exercise in normoxia, after 90 minutes of rest in hypoxia, after 15 minutes of exercise in hypoxia.

Study Arms (2)

HAPE+PFO

Adults with documented history of high-altitude pulmonary edema and a patent foramen ovale

HAPE

Adults with documented history of high-altitude pulmonary edema

Eligibility Criteria

• Age: 18 Years - 60 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)
• Sampling Method: Non-Probability Sample

Study Population

Individuals with documented history of high-altitude pulmonary edema and with or without a patent foramen ovale

You may qualify if:

• Males and females age \> 18 but \< 60 years of age at the time of signing the informed consent.
• Medically documented episode of noncardiogenic pulmonary edema occurring after exposure to hypoxia at high altitude.
• No other associated congenital cardiac or vascular abnormalities.
• Physically active, and able to perform endurance exercise.

You may not qualify if:

• Cardiac- or pulmonary-related medications.
• Known history of anemia, iron deficiency, iron supplementation (oral or intravenous) in the preceding 60 days.
• Systemic anticoagulation or aspirin use that cannot be temporarily held for the study.
• Non-cardiopulmonary disorders that adversely influence exercise ability (e.g. arthritis or peripheral vascular disease).
• Engaging in vigorous physical activity \[≥1 hour at ≥6 mets\] at ≥8,000 ft for \>2 days per week over the preceding 4 weeks, and residing at ≥8,000 ft for 3 or more consecutive nights in the preceding 30 days.
• History of any recent illnesses (e.g. viral respiratory infections) within 4 weeks of testing.
• Women who are pregnant (urine pregnancy test given to all women of childbearing age at the time of testing).
• Other conditions that would limit the patient's ability to complete the study procedures.

Sponsors & Collaborators

• University of Texas Southwestern Medical Center: lead

MeSH Terms

Conditions

Foramen Ovale, Patent; Altitude Sickness; Hypoxia; Motor Activity

Condition Hierarchy (Ancestors)

Heart Septal Defects, Atrial; Heart Septal Defects; Heart Defects, Congenital; Cardiovascular Abnormalities; Cardiovascular Diseases; Heart Diseases; Congenital Abnormalities; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Respiration Disorders; Respiratory Tract Diseases; Signs and Symptoms, Respiratory; Signs and Symptoms; Pathological Conditions, Signs and Symptoms; Behavior

Study Officials

• Benjamin D. Levine, M.D.

  The University of Texas Southwestern Medical Center Dallas

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Giorgio Manferdelli, Ph.D.

CONTACT

214-345-7134; giorgio.manferdelli@utsouthwestern.edu

Mary Childers

CONTACT

214-345-6459; marychilders@texashealth.org

Study Design

• Study Type: observational
• Observational Model: CASE CONTROL
• Time Perspective: PROSPECTIVE
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Professor of Medicine

Study Record Dates

• First Submitted: July 20, 2026
• First Posted: August 3, 2026
• Study Start (Estimated): September 15, 2026
• Primary Completion (Estimated): December 31, 2027
• Study Completion (Estimated): September 15, 2028
• Last Updated: August 3, 2026

Record last verified: 2026-07

Data Sharing

• IPD Sharing: Will not share