What are the diagnostic criteria and steps to diagnose Postural Orthostatic Tachycardia Syndrome (POTS)?

How to Diagnose POTS

POTS is diagnosed by demonstrating a sustained heart rate increase of ≥30 bpm (or ≥40 bpm in adolescents aged 12-19 years) within 10 minutes of standing or head-up tilt, in the absence of orthostatic hypotension, accompanied by symptoms of orthostatic intolerance. 1, 2

Core Diagnostic Criteria

The diagnosis requires three essential components to be present simultaneously:

1. Heart Rate Criteria

• Adults (≥20 years): Heart rate increase ≥30 bpm within 10 minutes of standing, or absolute standing heart rate >120 bpm 1, 2
• Adolescents (12-19 years): Heart rate increase ≥40 bpm within 10 minutes of standing 1, 2
• The heart rate elevation must be sustained throughout the 10-minute period 2

2. Absence of Orthostatic Hypotension

• Critical exclusion criterion: No sustained systolic BP drop ≥20 mmHg or diastolic BP drop ≥10 mmHg within 3 minutes of standing 1, 2, 3
• In patients with supine hypertension, a systolic BP drop ≥30 mmHg should be considered as orthostatic hypotension 1
• POTS can only be diagnosed when orthostatic hypotension is explicitly absent 2, 3

3. Symptoms of Orthostatic Intolerance

The following symptoms must develop upon standing and be relieved by sitting or lying down 1, 3:

Primary orthostatic symptoms:

• Light-headedness and dizziness 1, 3
• Palpitations (reflecting sinus tachycardia) 1, 3
• Tremor and generalized weakness 1, 3
• Blurred vision and other visual disturbances 1, 3
• Fatigue and lethargy 1, 3

Autonomic activation signs:

• Pallor, sweating, and nausea 1, 3
• Chest discomfort or pain 3

Non-specific associated symptoms:

• Headache 1, 3
• Cognitive difficulties ("brain fog") 2
• Exercise intolerance 3

Diagnostic Testing Protocol

Active Stand Test (First-Line Diagnostic Test)

Pre-test preparation: 2

• Patient should fast for 3 hours before testing 2
• Avoid nicotine, caffeine, theine, or taurine-containing drinks on the day of examination 2
• Perform testing in a quiet environment with temperature controlled between 21-23°C 2
• Ideally conduct tests before noon 2

Testing procedure: 2

1. Measure BP and heart rate after 5 minutes of lying supine
2. Have patient stand quietly and record measurements:
   • Immediately upon standing
   • At 2 minutes
   • At 5 minutes
   • At 10 minutes
3. Critical: Patient must stand quietly for the full 10 minutes, as heart rate increase may take time to develop 2
4. Document any symptoms that occur during the test 2

Tilt-Table Testing (When Active Stand Test is Inconclusive)

• Use head-up tilt of at least 60 degrees 1
• Apply the same heart rate and BP criteria as for active stand testing 2
• Consider tilt-table testing if clinical suspicion remains high despite negative stand test 2

Essential Workup to Exclude Mimics

Before confirming POTS diagnosis, exclude the following conditions:

Mandatory Laboratory Tests

• Thyroid function tests to exclude hyperthyroidism 2
• Complete blood count to exclude anemia 3

Cardiac Evaluation

• 12-lead ECG to rule out arrhythmias or conduction abnormalities 2
• Exclude inappropriate sinus tachycardia and other primary tachyarrhythmias 2, 3

Medication Review

• Review all cardioactive drugs that may cause tachycardia 2
• Assess for drugs causing hypovolemia (diuretics, alpha-blockers) 1

Additional Considerations

• Exclude dehydration and volume depletion 2
• Rule out pheochromocytoma in hyperadrenergic presentations 3
• Assess for anxiety disorders and primary psychiatric conditions 2

Clinical Context and Associated Conditions

Demographics

• Predominantly affects young women 1, 3
• Symptoms must persist for at least 3-6 months for formal diagnosis 2, 3

Commonly Associated Conditions

• Deconditioning 1, 3
• Recent infections or trauma 1, 3
• Chronic fatigue syndrome 1, 3
• Joint hypermobility syndrome and hypermobile Ehlers-Danlos syndrome 1, 3
• Screen for joint hypermobility using Beighton score (≥6/9 points in children before puberty) 2

Symptom Exacerbating Factors

Symptoms typically worsen: 1, 3

• In the morning
• With heat exposure
• After meals
• With exertion

Critical Diagnostic Pitfalls to Avoid

1. Inadequate testing duration: Failing to perform the active stand test for the full 10 minutes may miss delayed heart rate increases 2

2. Wrong age-specific criteria: Using adult criteria (≥30 bpm) instead of pediatric criteria (≥40 bpm for ages 12-19) leads to overdiagnosis in adolescents 2

3. Improper test conditions: Not maintaining proper fasting conditions or environmental controls can affect test results and lead to misdiagnosis 2

4. Failure to exclude orthostatic hypotension: POTS cannot be diagnosed if orthostatic hypotension is present 1, 2, 3

5. Missing secondary causes: Failing to exclude dehydration, medications, hyperthyroidism, anemia, or primary anxiety disorders leads to misdiagnosis 2, 3

6. Inadequate differentiation: Not distinguishing POTS from inappropriate sinus tachycardia, other tachyarrhythmias, or delayed orthostatic hypotension 1, 2

When to Expand Diagnostic Testing

If the diagnosis remains uncertain after initial evaluation, consider:

• Tilt-table testing when active stand test is negative but clinical suspicion remains high 2
• Autonomic function testing to assess for underlying autonomic neuropathies 4
• Evaluation for functional gastrointestinal or bladder disorders, which frequently coexist 4
• Assessment for fibromyalgia, sleep disturbances, and chronic headache patterns 3, 4