Clinical Features of Postural Orthostatic Tachycardia Syndrome (POTS)
POTS presents with severe orthostatic intolerance triggered by standing, characterized by marked tachycardia (≥30 bpm increase within 10 minutes of standing, or ≥40 bpm in ages 12-19) without orthostatic hypotension, predominantly affecting young women. 1, 2
Cardinal Hemodynamic Features
The defining hemodynamic abnormality is a sustained heart rate increase of ≥30 beats per minute within 10 minutes of standing in adults, or ≥40 bpm in adolescents aged 12-19 years. 1, 2 Standing heart rate frequently exceeds 120 bpm, though the diagnosis depends on the increment rather than absolute heart rate. 2
Critically, orthostatic hypotension must be absent—defined as no sustained systolic blood pressure drop ≥20 mmHg or diastolic drop ≥10 mmHg within 3 minutes of standing. 1, 2 This distinguishes POTS from other orthostatic disorders and is essential for diagnosis.
Primary Orthostatic Symptoms
The most prominent complaints develop upon standing and are relieved by sitting or lying down:
- Light-headedness and dizziness are the most common symptoms, often accompanied by generalized weakness and profound fatigue. 1
- Visual disturbances including blurred vision, tunnel vision, and tremor occur frequently. 1, 2
- Palpitations reflecting the excessive tachycardia are characteristic. 2, 3
- Presyncope is common, though frank syncope can occur. 3, 4
Autonomic Activation Manifestations
Sympathetic overactivity produces several characteristic features:
- Pallor and sweating reflect autonomic dysregulation. 1
- Nausea is a frequent complaint related to autonomic activation. 1, 3
- Chest discomfort or pain occurs commonly. 1, 3
Non-Specific Associated Features
Beyond orthostatic symptoms, patients experience:
- Headache is frequently reported. 1, 3, 5
- Exercise intolerance with postexertional malaise significantly impairs function. 1, 3, 5
- Cognitive complaints including "brain fog" and mental clouding are characteristic. 1, 2, 5
- Sleep disturbances contribute to overall disability. 1
- Abdominal discomfort may be present. 3
Temporal Patterns and Exacerbating Factors
Symptoms characteristically:
- Develop upon standing and are relieved by sitting or lying down—this is a critical diagnostic clue. 1, 2
- Worsen in the morning, with heat exposure, after meals, and with exertion. 1
- Must persist for at least 3 months (6 months in children) for formal diagnosis. 1, 2
Demographics and Associated Conditions
- Predominantly affects young women, often within 1-3 years of their growth spurt in adolescents. 1, 3
- Frequently coexists with deconditioning, recent infections, chronic fatigue syndrome, joint hypermobility syndrome, and hypermobile Ehlers-Danlos syndrome. 1, 2
Critical Diagnostic Pitfalls
POTS must be distinguished from several mimicking conditions:
- Inappropriate sinus tachycardia lacks the postural trigger and orthostatic symptom relief. 1, 2
- Anxiety disorders can produce tachycardia but lack the consistent postural relationship. 1
- Secondary causes including dehydration, anemia, hyperthyroidism, and pheochromocytoma must be excluded. 1, 2
- Medications (particularly cardioactive drugs) can produce similar symptoms. 2
The diagnosis requires demonstrating the hemodynamic criteria during a proper 10-minute active stand test performed in a quiet, temperature-controlled environment (21-23°C), with patients fasted for 3 hours and avoiding caffeine, nicotine, and stimulant-containing beverages. 2 Testing should ideally occur before noon. 2