Tests
1st tests to order
ECG
CBC
Test
Order CBC to exclude anemia as a potential cause of orthostatic tachycardia.[1][4] See Evaluation of anemia.
Result
normal
thyroid function tests
Test
Order thyroid function tests (thyroid-stimulating hormone, free thyroxine, free triiodothyronine) to exclude hyperthyroidism as a differential diagnosis.[1][4] See Graves disease.
Result
normal
electrolytes
morning serum cortisol
Test
Order morning serum cortisol level to exclude primary adrenal insufficiency (Addison disease) as a differential diagnosis.[4][44] See Primary adrenal insufficiency.
Result
normal
Tests to consider
Holter monitor
Test
Consider a 24-hour Holter monitor, which can help confirm the diagnosis by demonstrating the association between tachycardia and orthostatic changes.[2] A Holter monitor can also rule out supraventricular arrhythmias that may have a similar presentation to POTS.[2]
Result
tachycardia induced by orthostatic changes; no supraventricular arrhythmias[2]
echocardiogram
tilt-table test
Test
Organize a tilt-table test if:
The diagnosis is unclear after the initial assessment of orthostatic blood pressure and heart rate and you have a high suspicion of POTS.[2] In this scenario, a tilt-table test is helpful because it will provide an assessment of vital signs over a greater time period compared with a simple 10-minute standing test.
OR
The patient is not able to perform a 10-minute standing test.[1]
Result
orthostatic tachycardia with changing position
supine and upright plasma epinephrine and norepinephrine levels
Test
If the patient’s symptoms do not resolve or significantly improve, consider referral to a center experienced with the autonomic testing of POTS, where available, to organize further investigation of the underlying pathology.[2] This includes supine and upright plasma epinephrine and norepinephrine levels, which should be considered if hyperadrenergic POTS is suspected.[43] However, this should not be performed routinely because the significance for patient management and outcome is unclear.[2]
thermoregulatory sweat test
Test
If the patient’s symptoms do not resolve or significantly improve, consider referral to a center experienced with the autonomic testing of POTS, where available, to organize further investigation of the underlying pathology.[2] This includes a thermoregulatory sweat test, which should be considered to detect the autonomic neuropathy associated with POTS.[2] However, this should not be performed routinely because the significance for patient management and outcome is unclear.[2]
Result
abnormal patterns of body sweating
quantitative sudomotor axon reflex test
Test
If the patient’s symptoms do not resolve or significantly improve, consider referral to a center experienced with the autonomic testing of POTS, where available, to organize further investigation of the underlying pathology.[2] This includes a quantitative sudomotor axon reflex test if neuropathic POTS is suspected.[42] Neuropathic POTS is associated with peripheral venous pooling and reduced effective intravascular volume, which is caused by peripheral sympathetic denervation.[1][2] However, quantitative sudomotor axon reflex test should not be performed routinely because the significance for patient management and outcome is unclear.[2]
Result
abnormal postganglionic sympathetic sudomotor function[42]
valsalva maneuver
Test
If the patient’s symptoms do not resolve or significantly improve, consider referral to a center experienced with the autonomic testing of POTS, where available, to organize further investigation of the underlying pathology.[2] This includes the Valsalva maneuver with hemodynamic monitoring, which can detect autonomic dysfunction.[2][4] However, this should not be performed routinely because the significance for patient management and outcome is unclear.[2]
Result
excessive increase in blood pressure at the end of the maneuver if the patient has hyperadrenergic POTS[4]
deep breathing test
Test
If the patient’s symptoms do not resolve or significantly improve, consider referral to a center experienced with the autonomic testing of POTS, where available, to organize further investigation of the underlying pathology.[2] This includes the deep breathing test with hemodynamic monitoring, which can detect autonomic dysfunction.[4] However, this should not be performed routinely because the significance for patient management and outcome is unclear.[2]
Result
preserved vagal function is often found in POTS, demonstrated by the sinus arrhythmia ratio in response to deep breathing[4]
exercise testing
Test
Formal cardiopulmonary exercise testing can be useful as a measure of exercise capacity, which is often reduced in patients with POTS.
Result
exercise capacity baseline; often reduced in patients with POTS
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