How is Postural Orthostatic Tachycardia Syndrome (POTS) diagnosed?

Diagnosis of Postural Orthostatic Tachycardia Syndrome (POTS)

POTS is diagnosed by a sustained heart rate increase of ≥30 bpm (or ≥40 bpm in those 12-19 years of age) within 10 minutes of standing, without orthostatic hypotension, and with symptoms of orthostatic intolerance for at least 3 months. 1

Diagnostic Criteria

• Heart Rate Criteria:

  • Adults: ≥30 bpm increase within 10 minutes of standing
  • Adolescents (12-19 years): ≥40 bpm increase within 10 minutes of standing 1
  • Optimal diagnostic cutoffs:
    • Tilt test: 38 bpm increase
    • Active stand test: 29 bpm increase 1

• Blood Pressure: Absence of orthostatic hypotension (no drop >20 mmHg in systolic BP) 1

• Duration: Symptoms must be present for at least 3 months 1

• Symptoms: Frequent orthostatic intolerance symptoms including:

  • Dizziness/presyncope
  • Palpitations
  • Fatigue
  • Headache
  • Abdominal discomfort
  • Nausea 1, 2

Diagnostic Testing Algorithm

1. Initial Assessment:

   • Orthostatic vital signs or brief tilt table test (most sensitive method) 3
   • Resting 12-lead ECG 1
   • Complete blood count
   • Basic metabolic panel
   • Thyroid function tests
   • Cardiac biomarkers
   • C-reactive protein 1

2. Confirmatory Testing:

   • Active Standing Test: Patient lies supine for 5-10 minutes, then stands upright while heart rate and blood pressure are measured at baseline and at 2,5, and 10 minutes of standing 1

   OR

   • Tilt Table Test: Patient is secured to a table that tilts from horizontal to vertical position while heart rate and blood pressure are monitored 1

3. Additional Cardiac Evaluation:

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

4. Autonomic Function Testing (when available):

   • Quantitative sudomotor axon reflex test (QSART)
   • Valsalva maneuver
   • Deep breathing test
   • Pupillary responses 1

Exclusion of Other Conditions

POTS diagnosis requires ruling out other conditions that could explain sinus tachycardia:

• Anemia
• Dehydration
• Infection or fever
• Pain
• Hyperthyroidism
• Pheochromocytoma
• Primary anxiety disorders
• Anorexia nervosa
• Hyperventilation
• Cardioactive drugs
• Severe deconditioning from prolonged bed rest 1

POTS Subtypes

Identifying the POTS subtype can guide treatment approaches:

1. Neuropathic POTS:

   • Characterized by peripheral autonomic denervation
   • Often presents with blood pooling in lower extremities 1, 4

2. Hyperadrenergic POTS:

   • Characterized by excessive sympathetic nervous system activity
   • May present with more prominent palpitations, anxiety, tremor 1, 4

3. Hypovolemic POTS:

   • Characterized by reduced blood volume
   • Often presents with more severe orthostatic symptoms 1, 4

Clinical Pearls and Pitfalls

• POTS is often misdiagnosed as anxiety or deconditioning alone 3
• The condition is more common in females (5:1 female-to-male ratio) 5
• Typical age of onset is between 20-40 years 5
• Recent infections, including COVID-19, can trigger POTS (2%-14% of COVID-19 survivors develop POTS) 1
• POTS symptoms often overlap with chronic fatigue syndrome 1
• The reproducibility of physiological findings is important for diagnosis - a single positive test without consistent symptoms may not be sufficient 6
• Patients with POTS, supraventricular tachycardia, and mitral valve prolapse often have overlapping symptoms, requiring careful diagnostic differentiation 1