Splanchnic Venous Capacitance in Postural Tachycardia Syndrome

Conditions

• Postural Tachycardia Syndrome (POTS)

Eligibility Criteria

Sex

ALL

Age

18 Years - 50 Years

Healthy Volunteers

Accepted

Interventions

• Measurement of Splanchnic venous capacitance(SVC)done at Baseline and after 90 min of 75 g glucose in Healthy Controls POTS patients — DIAGNOSTIC_TEST
  While segmental bioimpedance is monitored, continuous positive airway pressure (CPAP) will be applied sequentially at 0, 4, 8, 12, and 16 cm H2O for about 30 seconds each. This positive airway pressure will increase the intrathoracic pressure, which is transmitted to the venous circulation. Pressure (CPAP pressure, X axis) - volume (splanchnic vascular volume measured by segmental impedance and expressed as % change from baseline, Y axis) relationships are then constructed to assess for splanchnic venous capacitance
• Measurement of Splanchnic venous capacitance(SVC)done at Baseline and after 90 min of 75 g glucose in Healthy Controls — DIAGNOSTIC_TEST
  While segmental bioimpedance is monitored, continuous positive airway pressure (CPAP) will be applied sequentially at 0, 4, 8, 12, and 16 cm H2O for about 30 seconds each. This positive airway pressure will increase the intrathoracic pressure, which is transmitted to the venous circulation. Pressure (CPAP pressure, X axis) - volume (splanchnic vascular volume measured by segmental impedance and expressed as % change from baseline, Y axis) relationships are then constructed to assess for splanchnic venous capacitance
• Compare change is SVC and SMA flow due to GIP antagonist GIP(3-30)NH2 — DRUG
  Participants with POTS will be randomize to either saline versus GIP(3-30)NH2 acute infusion. We will measure changes in 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 hr. Notably, we will assess changes in venous capacitance using segmental impedance to measure the effect of graded positive airway pressure (CPAP) on splanchnic blood volume.
• Compare change is SVC and SMA flow due to saline — DRUG
  Participants with POTS will be randomize to either saline versus GIP(3-30)NH2 acute infusion. We will measure changes in 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 hr. Notably, we will assess changes in venous capacitance using segmental impedance to measure the effect of graded positive airway pressure (CPAP) on splanchnic blood volume.

Study Details

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.

Key Dates

Start date

Feb 25, 2023

Status verified

Sep 2025

Primary completion

May 31, 2027

Completion

Jun 1, 2028

Study Design

Enrollment

50 participants (estimated)

Allocation

RANDOMIZED

Intervention model

CROSSOVER

Primary purpose

DIAGNOSTIC

Arms

• Active Comparator: Changes in Splanchnic venous capacitance(SVC) before and after a 75-g oral glucose challenge
  To compare and measure changes in 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 hr. between participants with POTS (Postural Tachycardia Syndrome) and Healthy Control group Various GIP hormones especially GLP-1, GLP-2, glucagon, and other GI hormones before and after a 75-gram oral glucose at different timepoints through out 3 hours of the study visit
• Placebo Comparator: Effect of GIP antagonist GIP(3-30)NH2 Vs Saline on splanchnic venous capacitance on POTS patients
  POTS patients who participated in Aim 1, will be and randomized to either saline versus GIP antagonist (GIP(3-30)NH2) in Visit 2. The changes in their splanchnic venous capacitance and superior mesenteric arterial flow will be measured, before and after a 75-g oral glucose challenge during supine and 45-degree head-up tilt positions (orthostatic challenge) for up to 3 hr. Notably, changes in venous capacitance will be assessed using segmental impedance to measure the effect of graded positive airway pressure (CPAP) on splanchnic blood volume.

Primary Outcome Measure

Change in splanchnic venous capacitance in Postural Orthostatic Tachycardia Syndrome [ Time Frame: Baseline up to 180 minutes post glucose challenge ]

Central Contacts

• Pedro J Ortiz, MD
  689-233-2623
  [email protected]
• Meena Golchha, MD
  615-322-3447
  [email protected]

Locations (1)

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