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Splanchnic Venous Capacitance in Postural Tachycardia Syndrome

Mechanism of Glucose-dependent Insulinotropic Polypeptide (GIP) on Splanchnic Venous Capacitance in Postural Tachycardia Syndrome

Who can join

Ages 18 to 50 · All sexes · Healthy volunteers welcome

Inclusion Criteria:

* Between 18 and 50years of age
* Cases: Diagnosis of POTS with presyncope symptoms after meals Or

Controls:

* With no significant past medical history, non-smokers and not on chronic medications.
* Body mass index (BMI) between 18.5 to 29.9 kg/m2
* If pre-menopausal women: must have regular menstrual cycle.

Exclusion Criteria:

* BMI above ≥30 kg/m2
* Irregular menstrual cycle
* Intolerance to CPAP.
* Chronic use of acetaminophen
* Heart problems: myocardial infarction, angina, heart failure, stroke
* Undergone any heart related procedures or stents or on pacemaker.
* Uncontrolled hypertension.
* Type 1 or type 2 diabetes mellitus
* Pregnant or breast-feeding women.
* Impaired liver function
* Impaired Kidney function test.
* Anemia (Hematocrit\<34%).
* Ongoing substance abuse.
* Subjects with abnormal EKG
* History of seizures.
* Diagnosed with neuropathy due to any reason
* History of neck surgery.
* Smoker,
* On statin therapy for high cholesterol
* Rheumatoid arthritis.
* On oral corticosteroids,
* Current infections
* Documented of moderate decrease in blood volume

About the study

Postural tachycardia syndrome (POTS) affects ≈3 million young people, characterized by chronic presyncopal symptoms characterized by dizziness, lightheadedness, and orthostatic tachycardia that occur while standing. Across-sectional survey found that 25% of these patients complains that meals rich in carbohydrates are among the factors that further exacerbate POTS's symptoms and cause a myriad of gastrointestinal symptoms.

The splanchnic circulation is the largest blood volume reservoir of the human body, storing ≈25% of the total blood volume and contributing to sudden, and large, fluctuations in the stroke volume (SV). The orthostatic changes in systemic hemodynamics are particularly magnified after meals, due to increased blood volume sequestration triggered by the release of gastrointestinal peptides with vasodilatory properties. The purpose of this study is to determine if the worsening orthostatic tachycardia and symptoms after glucose ingestion in POTS patients are due to a greater increase in splanchnic venous capacitance and excessive blood pooling on standing as compare to Healthy controls.

The study will also determine if glucose-induced GIP secretion increases splanchnic venous capacitance, orthostatic tachycardia and worsening POTS postprandial symptoms. For this purpose subjects will be further randomized to either saline versus GIP(3-30)NH2 acute infusion, to measure the changes their splanchnic venous capacitance and superior mesenteric arterial flow before and after a 75-g oral glucose challenge during supine and 45-degree head-up tilt positions (orthostatic challenge) for up to 3 hours.

What is being tested

• Measurement of Splanchnic venous capacitance(SVC)done at Baseline and after 90 min of 75 g glucose in Healthy Controls POTS patients (diagnostic test)
• Measurement of Splanchnic venous capacitance(SVC)done at Baseline and after 90 min of 75 g glucose in Healthy Controls (diagnostic test)
• Compare change is SVC and SMA flow due to GIP antagonist GIP(3-30)NH2 (drug)
• Compare change is SVC and SMA flow due to saline (drug)

Sponsor: Vanderbilt University Medical Center · Participants: 50 · Started: Feb 25, 2023

Contact the study team

• Pedro J Ortiz, MD · Phone: 689-233-2623
• Meena Golchha, MD · Phone: 615-322-3447

Official record on ClinicalTrials.gov — NCT05375968

Locations in the U.S.

Conditions

• Postural Orthostatic Tachycardia Syndrome

From ClinicalTrials.gov, data retrieved Sep 29, 2026. Each study sets its own eligibility; the study team decides who can join.