Phenotyping Mitochondrial and Immune Dysfunction in POTS With Targeted Clinical Intervention.

Inclusion criteria

• Age: 18-70 years old
• POTS, as defined by the presence of any of the following criteria:

• For patients age 20 or older, increase in heart rate ≥ 30 bpm within ten minutes of upright posture (tilt test or standing) from a supine position (For patients age 18-19, heart rate increase must be >40 bpm)
• Associated with related symptoms that are worse with upright posture and that improve with recumbency
• Chronic symptoms that have lasted for longer than six months
• In the absence of other disorders, medications, or functional states that are known to predispose to orthostatic tachycardia
• Baseline eating period > 12-hour window

Exclusion criteria

• Taking insulin within the last 6 months.
• Manifest diabetes, defined as HbA1c > 7.0% given a 0.3% margin of error in lab readings, or diagnosis of diabetes.
• Known inflammatory and/or rheumatologic disease.
• Active tobacco abuse or illicit drug use or history of treatment for alcohol abuse.
• Pregnant or breast-feeding women.
• Shift workers with variable (e.g. nocturnal) hours.
• Caregivers for dependents requiring frequent nocturnal care/sleep interruptions.
• Planned travel to a time zone with greater than a 3-hour difference during study period.
• History of a major adverse cardiovascular event within the past 1 year (acute coronary syndrome (ACS), percutaneous coronary intervention, coronary artery bypass graft surgery, hospitalization for congestive heart failure, stroke/transient ischemic attack (TIA)).
• Uncontrolled arrhythmia (i.e. rate-controlled atrial fibrillation/atrial flutter are not exclusion criteria).
• History of thyroid disease requiring dose titration of thyroid replacement medication(s) within the past 3 months (i.e. hypothyroidism on a stable dose of thyroid replacement therapy is not an exclusion).
• History of adrenal disease.
• History of malignancy undergoing active treatment, except non-melanoma skin cancer.
• Known history of type I diabetes.
• History of eating disorder.
• History of cirrhosis.
• History of stage 4 or 5 chronic kidney disease or requiring dialysis.
• History of HIV/AIDS.
• Currently enrolled in a weight-loss or weight-management program.
• On a special or prescribed diet for other reasons (e.g. Celiac disease).
• Currently taking any medication that is meant for, or has known effect on, appetite.
• Any history of surgical intervention for weight management.
• Uncontrolled psychiatric disorder (including history of hospitalization for psychiatric illness).
• A score of >16 on the Epworth Sleepiness Scale (ESS).
• Depression determined by the Beck Depression Inventory (BDI-II) (unless previously diagnosed and well-controlled)
• Failure to use the smartphone app for documentation (defined as <2 meals/day for ≥3 days during baseline).