Diagnostic Criteria for Tachycardia in Postural Orthostatic Tachycardia Syndrome (POTS)
POTS is diagnosed by demonstrating a sustained heart rate increase of ≥30 beats per minute (≥40 bpm in adolescents aged 12-19) within 10 minutes of standing or head-up tilt, in the absence of orthostatic hypotension, along with symptoms of orthostatic intolerance. 1, 2
Core Diagnostic Criteria
- Heart rate must increase by ≥30 beats per minute (bpm) within 10 minutes of standing or during head-up tilt testing 1, 3
- For adolescents aged 12-19 years, the heart rate increase should be >40 bpm 1, 2
- Standing heart rate is often ≥120 bpm in patients with POTS 1, 4
- Orthostatic hypotension must be absent (defined as systolic BP drop ≥20 mmHg or diastolic BP drop ≥10 mmHg within 3 minutes of standing) 1, 5
- Symptoms of orthostatic intolerance must be present (light-headedness, palpitations, tremor, weakness, blurred vision, fatigue) 1, 2
Testing Protocol
- Perform a 10-minute active stand test with continuous monitoring 1
- Measure blood pressure and heart rate after 5 minutes of lying supine 1
- Record measurements immediately upon standing, and at 2,5, and 10 minutes after standing 1
- Patient must stand quietly for the full 10 minutes as heart rate increase may take time to develop 1, 6
- Document any symptoms that occur during the test 1
Important Testing Considerations
- Testing should be performed in a quiet environment with temperature controlled between 21-23°C 5
- Patients should be fasted for 3 hours before the test 5
- Avoid nicotine and caffeine-, theine-, or taurine-containing drinks on the day of examination 5
- Tests should ideally be performed before noon 5
- Tilt-table testing may produce larger heart rate increases than active standing 6
- The European Society of Cardiology recommends tilt-table testing if the active stand test is inconclusive 1
Common Pitfalls in POTS Diagnosis
- Failure to perform the active stand test for the full 10 minutes may miss delayed heart rate increases 1
- Not distinguishing POTS from inappropriate sinus tachycardia or other tachyarrhythmias 1
- Overlooking that POTS may be associated with deconditioning, chronic fatigue syndrome, or joint hypermobility syndrome 1, 5
- Using the 30 bpm criterion for 30-minute tilt tests, as this has poor specificity (optimal cutoff at 30 minutes of tilt is 47 bpm) 6
- Not recognizing that tilt testing produces larger heart rate increases than active standing, affecting diagnostic specificity 6
Associated Symptoms to Evaluate
- Dizziness, light-headedness, weakness, fatigue, lethargy 1, 7
- Palpitations and sinus tachycardia 1, 7
- Visual disturbances, such as blurring or tunnel vision 1
- Cognitive difficulties, including "brain fog" 1, 8
- Headache and chest pain 1, 7
- Symptoms of gastrointestinal dysfunction 5, 8
Remember that POTS is a heterogeneous disorder with multiple potential pathophysiological mechanisms, including impaired sympathetically mediated vasoconstriction, excessive sympathetic drive, volume dysregulation, and deconditioning 3. The diagnosis should be made based on both the objective heart rate criteria and the presence of characteristic symptoms of orthostatic intolerance 1, 2.