Hemodynamic Effects of Compression in POTS
Condition: Postural Tachycardia Syndrome
MeSH terms: Postural Orthostatic Tachycardia Syndrome; Tachycardia; Syndrome
Study type: Interventional

Summary: 
      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:

        1. full abdomen and lower extremity compression

        2. abdominal only compression

        3. leg only compression

        4. 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: 
      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.
    

Intervention name(s): LifeWrap Compression Garment
Intervention type(s): Device
Intervention description(s): Non-Pneumatic Anti-Shock (NASG) compression garment comprised of neoprene with velcro closures.
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention 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)
Primary purpose: Treatment
Keywords: Tilt Table; Compression; Dysautonomia; POTS