Hemodynamic Effects of Compression in POTS

Study Overview
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Brief Summary
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When an individual with Postural Tachycardia Syndrome (POTS) stands up, their heart rate increases significantly (>30BPM) and they may experience symptoms such as lightheadedness, dizziness, shortness of breath, nausea and mental confusion. One commonly prescribed treatment for POTS is compression garments. Compression garments squeeze veins to help return blood back to the heart, which may decrease heart rate and symptoms on standing. However, there is little research about the effectiveness of compression in adults with POTS. In this study, the investigators will use the Lifewrap garment, which compresses the abdomen, pelvis and lower extremities, to evaluate the effectiveness of compression in POTS. The investigators will use a head up tilt (HUT) which will simulate standing. The study participant will participate in 4x 10 minute HUTs wearing 4 different compression configurations: full abdomen and lower extremity compression abdominal only compression leg only compression No compression The investigators hypothesize that with full compression, the participant's heart rate increase from lying down to upright will be lower than when they are not wearing any compression. The investigators will also ask the participant about their symptoms when they are upright. The results of this study could demonstrate the potential benefits of compression and what configuration is most effective. These findings could rapidly translate to the clinical setting, providing improved care.

Detailed Description
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Postural Tachycardia Syndrome (POTS) is a chronic form of orthostatic intolerance marked by a significant and sustained increase in heart rate (HR) upon positional change from supine to standing (>30 beats/min [bpm]) in the absence of orthostatic hypotension (<20/10 mmHg decrease). Symptoms must be present for >6 months and other causes of orthostatic tachycardia must be ruled out. Individuals with POTS report orthostatic symptoms including palpitations, lightheadedness, and mental clouding, which improve on recumbence. The vast majority of individuals diagnosed with POTS are women age 13-50 years. Upon standing, approximately 500 mL of blood immediately redistributes from the thorax down to the abdomen, buttocks and legs. This leads to sympathetic activation as the baroreceptors sense less pressure. In a healthy individual, HR initially increases 10-20 bpm, and the systolic blood pressure (BP) decreases by approximately 5 mmHg. However, in an individual with POTS, this compensatory mechanism is impaired and HR will increase by >30 bpm and remain at this elevated rate for the duration of standing. In some individuals with POTS, upon standing cerebral blood flow velocity decreases. In other individuals, oscillation of cerebral blood flow due to failure of cerebral autoregulatory mechanisms is observed. Current treatment of POTS involves pharmacological and non-pharmacological intervention including salt and fluid loading, exercise, and physical countermanuevers. There are no approved medications for use in POTS and all use is off label. Compression garments are also often prescribed. Abdominal/lower extremity compression garments provide pressure to the blood vessels in the legs, thighs and abdomen which can minimize blood pooling and lead to improved blood return to the heart. One such garment is the Lifewrap Non-pneumatic AntiShock garment (NASG), indicated in post-partum hypovolemia. A pediatric study (n=20) found that orthostatic tachycardia and symptoms were decreased during head up tilt (HUT), with the use of a different NASG compression garment vs. no compression. However, there is no data to validate the efficacy of compression in adults POTS, and also no data to determine which type of compression is most beneficial (e.g. lower leg only, abdomen only, combination). The investigators hypothesize that the use of the Lifewrap NASG compression garment in a fully applied configuration will decrease orthostatic tachycardia and orthostatic symptoms during a 10 minute HUT vs. no compression garment. The investigators will complete a 4-way randomized crossover study of HUTs with compression applied by the LifeWrap NSAG in at attempt to demonstrate decreased orthostatic tachycardia and increased orthostatic tolerance in individuals with POTS. If successful, this study could provide needed evidence that compression in POTS is a successful non-pharmacological treatment modality, and as well, what type of compression is the most beneficial to patients with this syndrome. These findings could rapidly translate to the clinical setting and improve patient care. The study participant will complete 4x 10min HUTs during a single study day. There will be 4 compression conditions based on strap configuration of the Lifewrap garment: (1) full abdominal and lower extremity compression, (2) abdominal only compression, (3) lower extremity only compression and (4) no compression. A pressure sensor will used to measure the magnitude of compression pressure applied. The study will be conducted on a tilt table in a human physiology research and procedure room. Each intervention phase in the protocol will involve a supine baseline assessment period of 10 minutes followed by a 10 min HUT (80 degrees). There will be a 20 min recovery periods between each HUT. The study will take approximately 4 hours. The study participant will be instrumented in a fasting state and on an empty bladder. The investigators will apply skin electrodes to continuously monitor heart rate and record an ECG. BP will be monitored continuously using a finger volume clamp method (Nexfin, Edwards Lifesciences) and calibrated with intermittent brachial cuff measurements (Vital-Guard 450C Patient Care Monitor, IVY Medical). From the continuous BP waveform, the investigators can obtain an estimate of stroke volume, cardiac output, and systemic vascular resistance (Modelflow). Middle cerebral blood flow velocity will be assessed using transcranial doppler.

Official Title
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Body Compression in Postural Tachycardia Syndrome (POTS): Effects on Orthostatic Tolerance

Conditions
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Postural Tachycardia Syndrome

Intervention / Treatment
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* Device: LifeWrap Compression Garment


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Physician diagnosis of Postural Tachycardia Syndrome (POTS) Age 18-60 years (we are an adult group and we do not see pediatric patients clinically and do not have appropriate pediatric expertise) Male and Female Able and willing to provide informed consent Ability to travel to Libin Cardiovascular Institute of Alberta Autonomic Testing Lab at the University of Calgary, Calgary, AB. Exclusion Criteria: Overt cause for postural tachycardia, i.e., acute dehydration Participants with somatization or severe anxiety symptoms will be excluded (as they may not tolerated study procedures) Pregnant women Inability to tolerate compression garment for the duration of the study Other factors which in the investigator's opinion would prevent the participant from completing the protocol, including poor compliance during previous studies

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 60 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: There will be 4 compression conditions based on strap configuration of the Lifewrap garment: full abdominal and lower extremity compression, abdominal only compression, lower extremity only compression and no compression. The order of these interventions will be randomized.
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Full Compression<br>The LifeWrap compression garment will be fully secured with all straps. | Device: LifeWrap Compression Garment<br>* Non-Pneumatic Anti-Shock (NASG) compression garment comprised of neoprene with velcro closures.<br>|
| Experimental: Abdominal and Pelvic Compression<br>The Lifewrap compression garment abdominal, pelvic and upper thigh straps only will be secured. | Device: LifeWrap Compression Garment<br>* Non-Pneumatic Anti-Shock (NASG) compression garment comprised of neoprene with velcro closures.<br>|
| Experimental: Lower Limb Compression<br>The Lifewrap compression garment calf and ankle straps only will be secured. | Device: LifeWrap Compression Garment<br>* Non-Pneumatic Anti-Shock (NASG) compression garment comprised of neoprene with velcro closures.<br>|
| No Intervention: No Compression<br>None of the LifeWrap compression garment straps will be secured. | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Orthostatic Heart Rate (HR) Change | The primary outcome measure will be the magnitude of HR change from supine to HUT (max HR between 5-10 min of HUT) for each study arm. | Maximum HR between 5-10min HUT MINUS the baseline (pre-tilt) HR | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Maximum Upright Heart Rate | The maximum heart rate during minutes 5-10 of each HUT. The maximum heart rate during each of the study arms will be compared. | During minutes 5-10 of the HUT | 
| Differences in Vanderbilt Orthostatic Symptom Score (VOSS) Symptom Rating | Subjective symptom scoring as reported by participant during each study arm. The VOSS evaluates 9 symptoms on a 0 to 10 scale with 0 being no symptom to 10 being worst ever symptom. The total score ranges from 0-90, with a higher score being more severe symptoms. The 9 symptoms are mental clouding, blurred vision, shortness of breath, rapid heartbeat, tremulousness, chest discomfort, headache, lightheadedness, and nausea. The participant's VOSS score will be compared across the 4 arms of this study. The VOSS score has been previously used in multiple publications | After t=10 of the 10min HUT (or sooner if HUT has to be terminated early due to symptoms) | 
| Change in Systolic Blood Pressure (SBP) | Change in continuous systolic blood pressure between supine and HUT during each study arm. | During the baseline before the HUT and the SBP correlating with the maximum HR during 5-10 min HUT, recorded at 1 min intervals. | 
| Changes in Stroke Volume | Change in Stroke Volume from supine to HUT in each of the study arms. | During the baseline before the HUT and the SV correlating with the maximum HR during 5-10 min HUT, recorded at 1 min intervals. | 
| Change in Cardiac Output (CO) | Change in Cardiac Output from supine to HUT in each of the study arms. | During the baseline before the HUT and the CO correlating with the maximum HR during 5-10 min HUT, recorded at 1 min intervals. | 
| Change in Systemic Vascular Resistance (SVR) | Change in Systemic Vascular Resistance from supine to HUT in each of the study arms. | During the baseline before the HUT and the SVRcorrelating with the maximum HR during 5-10 min HUT, recorded at 1min intervals. | 
| Change in Cerebral Blood Flow Velocity (CBFV) | Change in cerebral blood flow from supine to HUT in each of the study arms. | During the baseline before the HUT and the CBFV correlating with the maximum HR during 5-10 min HUT, recorded at 1 min intervals. | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Tilt Table, Compression, Dysautonomia, POTS