Compression Garments are a commonly prescribed treatment in Postural Orthostatic Tachycardia Syndrome (POTS). The effectiveness of a proof-of-concept compression garment has been demonstrated in an acute laboratory setting. It is not known if commercially available compression garments that participants wear in their every day lives are effective at improving heart rate and reducing symptoms in POTS. This trial will evaluate the use of commercially available waist-high and abdominal compression garments in adults diagnosed with POTS in a community setting.

Current treatment of Postural Orthostatic Tachycardia Syndrome (POTS) involves pharmacological and non-pharmacological intervention including salt and fluid loading, exercise, physical countermanuevers, and compression garments. Lower extremity compression garments provide mechanical external pressure to the blood vessels in the legs, thighs and abdomen, shifting blood back to the central circulation to increase preload and stroke volume. With increased stroke volume, cardiac output is maintained without excessive tachycardia. Compression garments are commonly prescribed as a non-pharmacological treatment in POTS, but previously little evidence validated their use. A recent proof-of-concept compression garment study performed by our research lab demonstrated significant HR and symptom reductions with compression, with adult POTS patients in an acute laboratory setting. The effectiveness of commercially available compression garments in a community setting in POTS patients is not known.

In this study, the researchers will use commercially or medically (by prescription) available waist-high compression garments (WHC) that POTS patients use in their daily life, to evaluate compression as a viable long-term treatment option. Additionally, the researchers will perform an optional sub-study of abdominal compression garments (AC), evaluating their effectiveness. Results from this study will be used to inform the practicality and effectiveness of compression garments in the community setting. These findings could rapidly translate to the clinical setting and improve patient care.

Primary Hypothesis: Body compression with commercially available WHC will acutely reduce orthostatic tachycardia, when compared to no compression, in a community setting.

Sub-Study Hypothesis: Body compression with commercially available AC will acutely reduce orthostatic tachycardia, when compared to no compression, in a community setting.

The participant will complete the study in a community setting. The participant will be provided with the study supplies including a Holter monitor to wear during the study. The duration of the study will be up to 4 days in total. The "With Medications" phase is 2 days and the "Without Medications" phase is 2 days. The first randomization is whether to do the WHC studies first after medications have been held for at least 24h or without holding the medications. If the participant will be in the AC Sub-Studies, then they will do those studies during the same window of holding medications (or not) as the WHC study. The second randomization would determine the order of WHC-AC vs. AC-WHC during each window

For each study day, there will be a total of 4 standing tests. Participants will first put on the Holter monitor at the beginning of the study day. The first standing test (OVS #1) will be performed 30 minutes after the participant takes their medications but before putting on the compression garment. The participant will then put on the compression garment. The second (OVS #2) standing test will be performed 30 minutes after putting on the compression garment. The third (OVS #3) standing test will be performed a minimum of 3 hours after putting on the compression garment. After a minimum of 3hours, the participant will then remove the compression garment. The fourth standing test (OVS #4) will be performed 30 minutes after removing the garment. Participants will record their symptoms after each standing test, as well as medications taken each day in the provided study booklet.

Inclusion Criteria:

• Physician diagnosis of Postural Tachycardia Syndrome (POTS)
• Resident of Canada
• Owns waist-high compression garment: medical grade or commercially available tights with a pressure rating provided (e.g. 15-18 mmHg, 20-30 mmHg, 30-40 mmHg)
• Optional Sub-Study: owns an abdominal compression garment (e.g. abdominal shapewear, waist high shorts)
• Able to participate in a 4-day study (2x2 day segments with a 5-day washout period)

Exclusion Criteria:

• Overt cause for postural tachycardia (i.e., acute dehydration, thyroid disease) that precludes POTS diagnosis
• Not a resident of Canada
• Participants with somatization or severe anxiety symptoms will be excluded
• Pregnant (self-reported)
• Inability to tolerate compression garments for the duration of the study
• Does not own a waist-high compression garment
• Other factors which in the investigator's opinion would prevent the participant from completing the protocol, including poor compliance during previous studies

It is not possible to mask participants to the compression garment intervention.