Diagnostic Workup for Postural Orthostatic Tachycardia Syndrome (POTS)
The diagnostic workup for POTS requires a focused orthostatic vital sign assessment with heart rate monitoring during position change, along with exclusion of other causes of orthostatic intolerance. The diagnosis is primarily based on demonstrating an excessive heart rate increase upon standing without orthostatic hypotension 1.
Diagnostic Criteria
POTS is diagnosed when the following criteria are met:
- Sustained heart rate increase ≥30 beats per minute (bpm) within 10 minutes of standing or head-up tilt (≥40 bpm in patients 12-19 years of age) 1
- Heart rate often exceeds 120 bpm during standing 1
- Absence of orthostatic hypotension (no sustained drop in systolic BP ≥20 mmHg) 1
- Symptoms of orthostatic intolerance lasting ≥3 months 1
- Symptoms improve when returning to a supine position 1
Key Components of the Workup
1. Orthostatic Vital Sign Assessment
- Active standing test: Measure heart rate and blood pressure supine and then after standing for 10 minutes 1
- Head-up tilt test: More controlled alternative to active standing, particularly useful when the diagnosis is uncertain 1
- Pattern recognition: Document the characteristic pattern of POTS showing rapid HR increase without significant BP drop 1
2. Symptom Assessment
Document presence of characteristic symptoms:
- Lightheadedness, dizziness
- Palpitations, tremulousness
- Generalized weakness
- Blurred vision
- Exercise intolerance
- Fatigue
- Additional symptoms: brain fog, headache, nausea 1
3. Exclusion of Alternative Diagnoses
Rule out conditions that may mimic or cause orthostatic intolerance:
- Orthostatic hypotension
- Cardiac arrhythmias
- Anemia
- Dehydration
- Hyperthyroidism
- Pheochromocytoma
- Medications causing tachycardia (sympathomimetics, anticholinergics) 1
- Spontaneous intracranial hypotension 1
4. Laboratory Testing
- Complete blood count (to rule out anemia)
- Basic metabolic panel (to assess hydration status)
- Thyroid function tests (to exclude hyperthyroidism)
- Catecholamines (in selected cases to rule out pheochromocytoma)
- Serum volume assessment (in selected cases) 1
5. Autonomic Function Testing
- Comprehensive autonomic assessment in specialized centers to characterize the subtype of POTS 1
- Testing should be performed by specialists trained in autonomic function testing 1
- Testing should be done in the morning in a temperature-controlled environment (21-23°C)
- Patient should be fasting for 3 hours and avoid caffeine, nicotine, and other stimulants 1
Pathophysiologic Subtyping
Identifying the underlying pathophysiologic mechanism helps guide treatment:
- Neuropathic POTS: Partial autonomic neuropathy with peripheral denervation 2
- Hypovolemic POTS: Reduced blood volume 2
- Hyperadrenergic POTS: Excessive sympathetic activation 2
Common Comorbidities to Assess
- Chronic fatigue syndrome
- Fibromyalgia
- Joint hypermobility/Ehlers-Danlos syndrome
- Mast cell activation syndrome
- Gastrointestinal dysmotility
- Migraine headaches 3, 4
Pitfalls to Avoid
- Failure to perform proper orthostatic testing: Measurements must be taken both supine and after standing for at least 10 minutes
- Misdiagnosing anxiety: While anxiety may coexist with POTS, the orthostatic tachycardia is physiologic, not psychogenic 1
- Missing deconditioning: Physical deconditioning can exacerbate POTS symptoms and should be assessed 5
- Overlooking medication effects: Certain medications can cause or worsen orthostatic tachycardia 1
- Incomplete differential diagnosis: Conditions like spontaneous intracranial hypotension can present with orthostatic symptoms and should be considered 1
The diagnostic approach should be systematic, focusing on documenting the characteristic heart rate increase upon standing while excluding other causes of orthostatic symptoms and tachycardia.