Diagnostic Criteria for Postural Orthostatic Tachycardia Syndrome (POTS)
POTS is diagnosed when a patient demonstrates a sustained heart rate increase of ≥30 beats per minute (≥40 bpm in adolescents aged 12-19 years) within 10 minutes of standing, in the absence of orthostatic hypotension, accompanied by symptoms of orthostatic intolerance that have persisted for at least 3 months. 1, 2, 3
Core Diagnostic Requirements
All five of the following components must be present for diagnosis 3:
1. Heart Rate Criteria
- Sustained heart rate increase of ≥30 bpm within 10 minutes of standing (or head-up tilt) 1, 2, 3
- ≥40 bpm increase required for adolescents aged 12-19 years 1, 2, 3
- Standing heart rate frequently exceeds 120 bpm 1, 3, 4
2. Blood Pressure Criteria
- Absence of orthostatic hypotension is mandatory 1, 2, 3
- Orthostatic hypotension is defined as systolic BP drop ≥20 mmHg or diastolic BP drop ≥10 mmHg within 3 minutes of standing 1, 3
- POTS cannot be diagnosed if orthostatic hypotension is present 1
3. Symptom Profile
Symptoms of orthostatic intolerance must be present and should improve upon returning to supine position 2, 3:
Primary orthostatic symptoms:
- Lightheadedness and dizziness (most common, present in 97.6% of patients) 2, 5
- Palpitations 1, 3
- Generalized weakness and fatigue 1, 2
- Blurred vision or visual disturbances 1, 2
- Tremulousness 2, 3
Autonomic activation signs:
Associated symptoms:
4. Duration Requirement
5. Temporal Pattern
- Symptoms develop upon standing and are relieved by sitting or lying down 1, 2
- Symptoms often worsen in the morning, with heat exposure, after meals, and with exertion 2
Diagnostic Testing Protocol
Active Stand Test (Preferred Method)
The American College of Cardiology recommends the following standardized approach 1:
Pre-test preparation:
- Patient should be fasted for 3 hours before testing 1
- Avoid nicotine, caffeine, theine, or taurine-containing drinks on the day of examination 1
- Testing should ideally be performed before noon 1
- Environment should be quiet with temperature controlled between 21-23°C 1
Testing procedure:
- Measure blood pressure and heart rate after 5 minutes of lying supine 1
- Record measurements immediately upon standing, and at 2,5, and 10 minutes after standing 1
- Patient must stand quietly for the full 10 minutes as heart rate increase may take time to develop 1
- Document any symptoms that occur during the test 1
Tilt-Table Testing
- Consider if active stand test is inconclusive but clinical suspicion remains high 1
- A negative stand test does not exclude POTS if clinical suspicion is high 1
Additional Diagnostic Workup
Essential tests to exclude alternative diagnoses:
- 12-lead ECG to rule out arrhythmias or conduction abnormalities 1
- Thyroid function tests to exclude hyperthyroidism 1
- Medication review, especially cardioactive drugs 1
- Detailed medical history including family history 1
Critical Diagnostic Pitfalls to Avoid
Testing errors:
- Failure to perform the active stand test for the full 10 minutes may miss delayed heart rate increases 1
- Not maintaining proper fasting conditions can affect test results and lead to misdiagnosis 1
Differential diagnosis confusion: POTS must be distinguished from 1, 2:
- Inappropriate sinus tachycardia
- Anxiety disorders
- Dehydration
- Anemia
- Hyperthyroidism
- Pheochromocytoma
- Vasovagal syncope (note: syncope is rare in POTS and typically only occurs with vasovagal reflex activation) 3
Associated Conditions to Evaluate
POTS frequently coexists with 1, 2:
- Deconditioning
- Recent infections or trauma
- Chronic fatigue syndrome
- Joint hypermobility syndrome or hypermobile Ehlers-Danlos syndrome
- Gastrointestinal dysfunction