What tests are used to diagnose Postural Orthostatic Tachycardia Syndrome (POTS)?

Diagnostic Tests for POTS

The diagnosis of POTS requires a 10-minute active stand test demonstrating a sustained heart rate increase of ≥30 beats per minute (≥40 bpm in those <19 years) or heart rate ≥120 bpm, in the absence of orthostatic hypotension, with symptoms lasting >30 seconds. 1

Primary Diagnostic Test: 10-Minute Active Stand Test

The 10-minute active stand test is the cornerstone diagnostic procedure for POTS and should be performed as initial outpatient testing. 1 This test involves:

• Measuring blood pressure and heart rate after 5 minutes of lying supine 1
• Measuring immediately upon standing 1
• Measuring at 2,5, and 10 minutes after standing 1
• Ensuring the patient stands quietly for the full 10 minutes, as heart rate increases may take time to develop 1

Critical diagnostic criteria:

• Heart rate increase >30 bpm in adults ≥19 years (or >40 bpm in those <19 years) 1
• Heart rate reaching >120 bpm during the test 1
• Tachycardia must last >30 seconds and be accompanied by symptoms 1
• Absence of orthostatic hypotension (defined as systolic BP drop ≥20 mmHg or diastolic BP drop ≥10 mmHg within 3 minutes) 1

Alternative Diagnostic Test: Tilt Table Testing

Tilt table testing can diagnose POTS when the active stand test is inconclusive or when more controlled monitoring is needed. 1 The test involves:

• Head-up tilt of at least 60 degrees 1
• Continuous beat-to-beat blood pressure and ECG monitoring 1
• Observation period <10 minutes 1
• Documentation of inappropriate heart rate increase without concomitant blood pressure fall 1

The tilt table test allows for more precise hemodynamic monitoring and can help differentiate POTS from other orthostatic syndromes, including delayed orthostatic hypotension and vasovagal syncope. 1

Essential Baseline Evaluation Before POTS Testing

Before performing specific POTS diagnostic tests, the following baseline assessments are mandatory:

History focusing on:

• Symptoms of orthostatic intolerance (lightheadedness, palpitations, tremor, weakness, blurred vision, fatigue) 1
• Exercise intolerance and tachycardia patterns 1
• Symptoms of autonomic dysfunction (GI dysmotility, urinary retention/incontinence, sexual dysfunction) 1
• Recent infection or trauma 1
• Joint hypermobility 1

Physical examination including:

• Complete cardiovascular examination 1
• Assessment for joint hypermobility syndrome 1
• Evaluation for mitral valve prolapse 2

12-lead ECG to exclude:

• Arrhythmias 1
• Inappropriate sinus tachycardia 1
• Other cardiac conduction abnormalities 1

Ambulatory Cardiac Monitoring

Ambulatory rhythm monitoring should be considered to exclude arrhythmia and define the pattern of heart rate elevation. 1

• 24- to 48-hour Holter monitor for defining heart rate patterns 1
• Extended Holter monitor or event monitor for episodic palpitations 1
• Mobile health devices capable of heart rate and ECG monitoring for surveillance during recovery 1

This monitoring helps differentiate POTS from inappropriate sinus tachycardia, particularly by assessing whether heart rate slows at night. 1

Functional Capacity Assessment

A 6-minute walk test can assess functional capacity while monitoring heart rate and oxygen saturation. 1 This test is particularly useful for:

• Evaluating exercise intolerance 1
• Monitoring heart rate response to activity 1
• Assessing oxygen saturation during exertion 1

Additional Testing for Comprehensive Evaluation

When POTS is suspected, particularly in atypical presentations, additional testing may be warranted:

Autonomic function testing in a dedicated laboratory to characterize cardiovascular sympathetic and parasympathetic function 1, 2, 3

Laboratory tests to evaluate for underlying conditions:

• Complete blood count 1
• Basic metabolic panel 1
• Thyroid function tests 1
• Volume status assessment 3

Cardiac imaging:

• Echocardiogram when structural heart disease is suspected 1
• Evaluation for mitral valve prolapse 2

Critical Diagnostic Pitfalls to Avoid

Do not diagnose POTS if orthostatic hypotension is present - the absence of orthostatic hypotension is a mandatory criterion. 1 If both tachycardia and blood pressure drop occur, consider delayed orthostatic hypotension followed by reflex syncope instead. 1

Ensure tachycardia is sustained and positional - transient heart rate increases or tachycardia unrelated to position suggest alternative diagnoses like inappropriate sinus tachycardia. 1

Recognize that physiologically appropriate heart rate increases should not automatically indicate autonomic dysregulation - increases in heart rate may be appropriate responses to deconditioning or other physiologic states. 1

Perform testing in appropriate conditions - tests should be conducted in a temperature-controlled environment (21-23°C), with patients fasted for 3 hours and avoiding nicotine, caffeine, theine, or taurine-containing drinks on the day of examination. 1

Pathophysiologic Subtype Evaluation

While not required for diagnosis, identifying the underlying pathophysiologic mechanism can guide treatment:

• Peripheral denervation assessment through autonomic testing 2, 3, 4
• Hyperadrenergic state evaluation through plasma catecholamine levels 2, 3, 4
• Hypovolemia assessment through volume status estimation 2, 3, 4
• Autoimmune workup in atypical cases, particularly with recent infection 5, 4