What is the initial workup for a patient suspected of having Postural Orthostatic Tachycardia Syndrome (POTS)?

Initial Workup for Suspected Postural Orthostatic Tachycardia Syndrome (POTS)

The initial workup for suspected POTS should include orthostatic vital sign measurement (heart rate and blood pressure), 12-lead ECG, complete blood count, basic metabolic panel, thyroid function tests, and cardiac biomarkers. 1

Diagnostic Criteria

POTS is diagnosed when the following criteria are met:

• Sustained heart rate increase of ≥30 bpm (or ≥40 bpm in those 12-19 years) within 10 minutes of standing
• Absence of orthostatic hypotension (no drop >20 mmHg in systolic BP)
• Symptoms of orthostatic intolerance present for at least 3 months 1

Initial Evaluation Steps

1. Orthostatic Vital Sign Assessment

• Active Standing Test: Have patient lie supine for 5-10 minutes, then stand for 10 minutes
• Head-up Tilt Table Test: Gold standard test for POTS diagnosis 1
  • Performed in a dedicated laboratory with beat-to-beat BP and ECG monitoring
  • Patient should fast 2-4 hours before test
  • Avoid nicotine, caffeine, theine, or taurine-containing drinks on day of examination
  • Room temperature controlled between 21-23°C
  • 70-degree tilt for at least 10 minutes with continuous monitoring

2. Laboratory Testing

• Complete blood count
• Basic metabolic panel
• Thyroid function tests
• Cardiac biomarkers (troponin)
• C-reactive protein 1

3. Cardiac Assessment

• 12-lead ECG
• Echocardiogram
• 24-48 hour Holter monitor or longer ambulatory rhythm monitoring 1

Patient Characteristics to Note

• Demographics: POTS predominantly affects young women (female predominance ~80%)
• Common symptoms: light-headedness, dizziness, palpitations, tremulousness, weakness, blurred vision, fatigue, exercise intolerance, headache, nausea, abdominal discomfort 1
• Associated conditions: deconditioning, chronic fatigue syndrome, joint hypermobility syndrome, recent infections, trauma 1

Red Flags for "Atypical" POTS Requiring Expanded Workup

• Older age at onset
• Male gender
• Prominent syncope
• Examination abnormalities other than joint hyperextensibility
• Disease refractory to first-line treatments 2

Differential Diagnosis Considerations

When evaluating a patient with suspected POTS, it's important to distinguish from other orthostatic disorders:

• Classical Orthostatic Hypotension: BP decrease ≥20 mmHg systolic or ≥10 mmHg diastolic within 3 minutes of standing
• Initial Orthostatic Hypotension: BP decrease >40 mmHg systolic within 15 seconds of standing, with rapid recovery
• Delayed Orthostatic Hypotension: BP decrease occurring beyond 3 minutes of standing
• Orthostatic Vasovagal Syncope: Features both hypotension and bradycardia 1

Important Clinical Considerations

• The optimal diagnostic heart rate increase cutoffs are 38 bpm for tilt test and 29 bpm for active stand 1
• About half of patients report an antecedent illness presumed to be of viral origin 3
• The three major pathophysiologic mechanisms include partial autonomic neuropathy, hypovolemia, and hyperadrenergic state 4

POTS is a clinical syndrome with multiple heterogeneous disorders and overlapping features, making it essential to conduct a thorough initial evaluation to establish the diagnosis, identify co-morbid conditions, and exclude conditions that could cause or mimic the syndrome.