What are the clinical findings for Postural Orthostatic Tachycardia Syndrome (POTS)?

Clinical Findings in Postural Orthostatic Tachycardia Syndrome (POTS)

Postural Orthostatic Tachycardia Syndrome (POTS) is characterized by a sustained heart rate increase of ≥30 bpm in adults (≥40 bpm in adolescents aged 12-19) within 10 minutes of standing, absence of orthostatic hypotension, and symptoms of orthostatic intolerance persisting for at least 3 months. 1

Diagnostic Criteria

• Heart Rate Increase:

  • ≥30 bpm in adults within 10 minutes of standing 2, 1
  • ≥40 bpm in adolescents aged 12-19 years 1
  • Heart rate often exceeds 120 bpm when standing 2, 3

• Blood Pressure Response:

  • Absence of orthostatic hypotension (no sustained drop in systolic BP ≥20 mmHg) 1
  • In hyperadrenergic POTS: systolic BP increase ≥10 mmHg during standing 4

• Duration of Symptoms:

  • Symptoms must persist for at least 3 months 1

Clinical Symptoms

The primary symptoms of orthostatic intolerance in POTS include:

• Cardiovascular:

  • Palpitations 2, 1
  • Tachycardia 5

• Neurological:

  • Dizziness/lightheadedness 2, 1, 5, 6
  • Mental clouding/brain fog 1, 7
  • Headache 1, 5, 3
  • Blurred vision 1, 6

• General:

  • Extreme fatigue 1, 5, 7
  • Generalized weakness 2, 1, 6
  • Exercise intolerance 7
  • Tremulousness/tremor 2, 1

• Gastrointestinal:

  • Abdominal discomfort 5
  • Nausea 2, 5

• Key Feature:

  • All symptoms worsen with upright posture and improve upon returning to supine position 1

Associated Conditions

POTS is frequently associated with:

• Deconditioning 2, 3
• Recent infections (including post-COVID-19) 2, 1
• Chronic fatigue syndrome 2, 3
• Joint hypermobility syndrome/Ehlers-Danlos syndrome 3, 6
• Functional gastrointestinal disorders 3
• Bladder disorders 3
• Chronic headache 3
• Fibromyalgia 3
• Sleep disturbances 3

Pathophysiological Subtypes

POTS is heterogeneous with several pathophysiological mechanisms:

1. Neuropathic POTS:

   • Impaired sympathetically mediated vasoconstriction 3
   • Peripheral autonomic denervation 2

2. Hyperadrenergic POTS:

   • Excessive sympathetic drive 3
   • Elevated standing norepinephrine levels (≥600 pg/mL) 4
   • Systolic BP increase ≥10 mmHg during standing 4

3. Hypovolemic POTS:

   • Volume dysregulation 3
   • Low blood volume 7

4. Deconditioning-related POTS:

   • Often occurs after period of inactivity from illness or injury 5
   • Common in adolescents within 1-3 years of growth spurt 5

Laboratory and Diagnostic Findings

• Autonomic Testing:

  • Positive tilt table test showing heart rate increase without orthostatic hypotension 1
  • Optimal diagnostic heart rate increase cutoff:
    • 38 bpm on tilt test 1
    • 29 bpm on active stand test 1

• Laboratory Findings:

  • Elevated standing plasma norepinephrine (≥600 pg/mL in hyperadrenergic POTS) 7, 4
  • Normal supine norepinephrine levels 4

• Exclusionary Testing:

  • Normal thyroid function tests 1
  • Normal complete blood count (to rule out anemia) 1
  • Normal basic metabolic panel 1
  • Normal cardiac biomarkers 1

Important Clinical Considerations

• Significant diagnostic delay is common (8-10 years from symptom onset to diagnosis) 6
• Family history of syncope or presyncope is common (66% in some studies) 6
• Symptoms not directly attributable to orthostatic intolerance are often present 3
• Cognitive, behavioral factors and anxiety may contribute to symptom chronicity 3
• Patients often have high functional disability 7

POTS requires careful differentiation from other causes of inappropriate sinus tachycardia, chronic fatigue, and unexplained dizziness in otherwise healthy individuals 3.