Orthostatic Vital Signs (Stand Test)
The test performed to assess her possible POTS diagnosis was orthostatic vital signs measurement, also known as a stand test, where heart rate and blood pressure are measured supine for at least 5 minutes, then standing for up to 10 minutes. 1
Diagnostic Approach for POTS
The Canadian Cardiovascular Society guidelines clearly specify that for most patients with suspected POTS, a detailed history and physical examination with orthostatic vital signs is sufficient to establish diagnosis and initiate treatment 1. This is a strong recommendation based on high-quality evidence.
How the Stand Test is Performed
The diagnostic protocol requires:
- Supine position: Measure heart rate and blood pressure after lying flat for at least 5 minutes
- Standing position: Measure continuously for up to 10 minutes after standing
- Diagnostic criteria: Heart rate increase of ≥30 bpm in adults (≥40 bpm in ages 12-19) sustained for at least 2 consecutive recordings separated by at least 1 minute after the first minute of standing 1
- Minimum standing heart rate: Must reach ≥90 bpm in adults (≥100 bpm in teenagers) to meet POTS criteria 1
Important Diagnostic Nuances
The tachycardia must be sustained and persistent, not just a transient spike on initial standing. Initial heart rate increases can occur with initial orthostatic hypotension and do not constitute POTS 1. The excessive tachycardia typically becomes more pronounced during the first 10 minutes upright.
Symptoms must correlate with the heart rate increase during the stand test. Asymptomatic patients who meet hemodynamic criteria should not be diagnosed with POTS 1.
When Additional Testing is NOT Needed
The guidelines explicitly state that tilt table testing, autonomic nervous system testing, plasma catecholamine testing, autoimmune workup, blood volume assessment, neuroimaging, and neurological studies are NOT recommended routinely 1. This is important because many clinicians over-test for POTS.
Tilt Table Testing is Reserved For:
- Complicated patients
- Patients refractory to initial therapy
- Diagnostic clarification at specialist centers 1
Most patients with POTS will not need tilt table testing 1.
Basic Laboratory Work
Initial assessment should include routine blood tests to exclude secondary causes:
- Complete blood count
- Electrolytes (Na+, K+, Cl-)
- Renal function (creatinine, urea)
- Ferritin
- Thyroid stimulating hormone
- Morning cortisol level 1
These tests identify conditions that can mimic or cause orthostatic tachycardia (anemia, thyroid disease, adrenal insufficiency, dehydration).
Common Pitfall to Avoid
Do not order extensive cardiac testing routinely. Echocardiogram, external ECG monitoring, and exercise stress tests should only be considered when there is specific concern for structural heart disease or non-sinus node arrhythmias 1. The normal sinus rhythm EKG with heart rate of 91 bpm already excludes primary cardiac arrhythmias.