Postural Orthostatic Tachycardia Syndrome Clinical Trial
Official title:
Mechanism of Chemoreflex and Baroreflex Alterations Causing Postural Tachycardia Syndrome in POTS Patients With Orthostatic Hyperpnea and Hypocapnia
Postural tachycardia syndrome (POTS) is the most common chronic cause of postural lightheadedness, and upright confusion afflicting many Americans, mostly young women. Many POTS patients hyperventilate by increasing their depth of breathing that produces tachycardia, alters blood flow and blood pooling in the body and importantly reduces brain blood flow causing "brain fog". In this proposal the investigators will demonstrate in young women that abnormal repeated brief impairment of blood pressure and brain flow just after standing sensitizes the body's oxygen sensor in POTS to respond as if it were in a low oxygen environment causing hyperventilation and its consequences. In this project the investigators will use various drugs that will help to understand the mechanisms that cause POTS in this unique subset of POTS patients who hyperventilate.
Status | Recruiting |
Enrollment | 30 |
Est. completion date | August 31, 2024 |
Est. primary completion date | August 31, 2023 |
Accepts healthy volunteers | Accepts Healthy Volunteers |
Gender | Female |
Age group | 15 Years to 39 Years |
Eligibility | Inclusion Criteria: - The investigators will recruit female POTS cases (N=80) and healthy female control subjects (N=40) aged 15-39 years, matched for BMI. POTS is a disease in which 80-90% are females. Therefore, the investigators will only recruit female POTS patients and controls. Exclusion Criteria: - Any subjects with systemic disease or who cannot stop taking prescribed medications for at least 2 weeks prior to study. |
Country | Name | City | State |
---|---|---|---|
United States | NewYork Medical College | Hawthorne | New York |
Lead Sponsor | Collaborator |
---|---|
New York Medical College |
United States,
Type | Measure | Description | Time frame | Safety issue |
---|---|---|---|---|
Primary | Orthostatic tachycardia | Heart rate (beats per minute) delimit the orthostatic response. Two separate orthostatic tests are used: a standing test and a 70 degree upright tilt test. The standing test will delineate the carotid blood flow signal that sensitizes the carotid body chemoreflex. The tilt test will delineate the effects of sustained tachyardia (and hyperpnea) on systemic hemodynamics and breathing. | Baseline in all subjects | |
Primary | Orthostatic Blood Pressure Changes | Blood pressure (mmHg) delimit the orthostatic response. Two separate orthostatic tests are used: a standing test and a 70 degree upright tilt test. The standing test will delineate the carotid blood flow signal that sensitizes the carotid body chemoreflex. The tilt test will delineate the effects of sustained tachyardia (and hyperpnea) on systemic hemodynamics and breathing. | Baseline in all subjects | |
Primary | Orthostatic Changes in Systemic Vascular Resistance | Systemic vascular resistance (mmHg·min·mL-1) delimit the orthostatic response. Two separate orthostatic tests are used: a standing test and a 70 degree upright tilt test. The standing test will delineate the carotid blood flow signal that sensitizes the carotid body chemoreflex. The tilt test will delineate the effects of sustained tachyardia (and hyperpnea) on systemic hemodynamics and breathing. | Baseline in all subjects | |
Primary | Orthostatic Blood Volume Changes | Central Blood Volume in liters (L) delimit the orthostatic response. Two separate orthostatic tests are used: a standing test and a 70 degree upright tilt test. The standing test will delineate the carotid blood flow signal that sensitizes the carotid body chemoreflex. The tilt test will delineate the effects of sustained tachyardia (and hyperpnea) on systemic hemodynamics and breathing. | Baseline in all subjects | |
Primary | Orthostatic Changes in Segmental Blood Flow | Segmental Blood Flows (ml•min-1•100 ml tissue-1) delimit the orthostatic response. Two separate orthostatic tests are used: a standing test and a 70 degree upright tilt test. The standing test will delineate the carotid blood flow signal that sensitizes the carotid body chemoreflex. The tilt test will delineate the effects of sustained tachyardia (and hyperpnea) on systemic hemodynamics and breathing. | Baseline in all subjects | |
Primary | Orthostatic Changes in Cerebral Blood Flow | Cerebral Blood Flow (cm/s) delimit the orthostatic response. Two separate orthostatic tests are used: a standing test and a 70 degree upright tilt test. The standing test will delineate the carotid blood flow signal that sensitizes the carotid body chemoreflex. The tilt test will delineate the effects of sustained tachyardia (and hyperpnea) on systemic hemodynamics and breathing. | Baseline in all subjects | |
Primary | Orthostasis Induced Rate of Breathing | Changes in the rate of breathing (breaths per minute) will be determined in all subjects before and after being tilted upright on a tilt table. | Baseline in all subjects | |
Primary | Orthostasis Induced Depth of Breathing | Changes in the depth of breathing (L of inhaled air per minute) will be determined in all subjects before and after being tilted upright on a tilt table. | Baseline in all subjects | |
Primary | Measurement of chemoreflex sensitivity carotid body chemoreflex and central chemoreflex | Paired hypoxia and isocapnic hyperoxia determine the carotid body chemoreflex sensitivity; measurements of ventilation and sympathetic activation using Muscle Sympathetic Nerve Activity (MSNA - mean burst frequency and normalized mean burst area and expressed as arbitrary units (AU) per minute) define the responses. Similarly, measurement of during isocapnic hyperoxia and hypercapnic hyperoxia determine central chemoreflex stressors - measure sympathetic activity as responses. | Baseline in all subjects | |
Primary | Effects of chemoreflex activation on baroreflexfunction and the effects of baroreflex on chemoreflex sensitivity | Supine chemoreflex activation using controlled gas conditions which are: isocapnic hypoxia and isocapnic hyperoxia to measure carotid body reflex; hyperoxic isocapnia and hyperoxic hypercapnia to measure central chemoreflexes. Hyperoxia silences peripheral chemoreceptors and will normalize baroreflex and tilt responses) should alter baroreflex function measured as the change in RR Interval (reciprocal of heart rate) in milliseconds per millimeter of mercury change in systolic blood pressure). This will be performed both supine and during 45 degree tilting which will activate the baroreflexes and reduce chemoreflex responses. | Baseline in all subjects | |
Secondary | Systemic changes in leg blood volumes during orthostatic testing. | The investigators will measure changes in leg blood volume using impedance plethysmography methods which measures changes in electrical resistance (in Ohms) of the legs before and after tilt table testing which is expressed as ml•min-1•100 ml tissue-1. | Baseline in all subjects | |
Secondary | Systemic changes in abdominal blood volumes during orthostatic testing. | The investigators will measure changes in abdominal blood volume using impedance plethysmography methods which measures changes in electrical resistance (in Ohms) of the abdomin before and after tilt table testing which is expressed as ml•min-1•100 ml tissue-1. | Baseline in all subjects |
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