What are the diagnostic steps for Postural Orthostatic Tachycardia Syndrome (POTS)?

From the Guidelines

Diagnosing Postural Orthostatic Tachycardia Syndrome (POTS) requires a systematic approach centered on documenting an abnormal heart rate increase upon standing, as outlined in the 2018 European Heart Journal guidelines 1. The primary diagnostic test is the orthostatic standing test, where the patient's heart rate and blood pressure are measured while lying down for 5-10 minutes, then immediately upon standing and at intervals for 10 minutes. A diagnosis of POTS is confirmed when there is a sustained heart rate increase of at least 30 beats per minute (or ≥40 bpm in those aged 12-19) within 10 minutes of standing, without orthostatic hypotension (a drop in blood pressure >20/10 mmHg), as defined in the 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope 1. Some key points to consider in the diagnosis of POTS include:

• A tilt table test may be used as an alternative, providing more controlled conditions.
• Before diagnosis, comprehensive blood work should be performed to rule out other conditions that could cause similar symptoms, including complete blood count, thyroid function tests, and electrolyte panels, as recommended in the 2018 ESC guidelines for the diagnosis and management of syncope 1.
• A 12-lead ECG is also recommended to exclude cardiac arrhythmias.
• Additional testing may include 24-hour Holter monitoring, echocardiogram, and autonomic function tests.
• It's essential to exclude other causes of orthostatic symptoms such as dehydration, anemia, medication effects, and endocrine disorders before confirming a POTS diagnosis, as emphasized in the 2009 guidelines for the diagnosis and management of syncope 1.
• Patients should also complete a detailed symptom diary documenting positional changes and associated symptoms to aid in diagnosis. The pathophysiology of POTS is debated and likely heterogeneous, involving deconditioning, immune-mediated processes, excessive venous pooling, and a hyperadrenergic state, as discussed in the 2018 European Heart Journal guidelines 1. POTS is frequently associated with deconditioning, recent infections, chronic fatigue syndrome, joint hypermobility syndrome, and a spectrum of non-specific symptoms such as headache and chest pain. The standing heart rate is often >120 bpm, and symptoms associated with POTS include those that occur with standing, such as lightheadedness, palpitations, as well as those not associated with particular postures, like bloating, nausea, diarrhea, abdominal pain, and systemic symptoms like fatigue, sleep disturbance, and migraine headaches, as described in the 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope 1.

From the Research

Diagnostic Steps for Postural Orthostatic Tachycardia Syndrome (POTS)

To diagnose POTS, the following steps can be taken:

• A focused history and examination to identify symptoms of orthostatic intolerance, such as brain hypoperfusion and sympathetic overaction 2
• Tests to evaluate orthostatic tolerance, including:
  • Head-up tilt (HUT) testing to assess heart rate and blood pressure responses to upright posture 3, 2, 4
  • Active stand testing to evaluate heart rate and blood pressure responses to standing 3
• Estimation of volume status to assess for hypovolemia 2, 5
• Evaluation of peripheral denervation and hyperadrenergic state, including serum catecholamine levels and heart rate variability testing 2, 5, 4
• Assessment for other conditions that may mimic POTS, such as orthostatic hypotension or other forms of autonomic dysfunction 6, 5

Diagnostic Criteria

The diagnostic criteria for POTS include:

• An increase in heart rate of ≥30 bpm within 10 minutes of assuming an upright position, without orthostatic hypotension 3, 2, 5
• Symptoms of orthostatic intolerance, such as lightheadedness, dizziness, or syncope 2, 5
• Exclusion of other conditions that may cause similar symptoms, such as orthostatic hypotension or other forms of autonomic dysfunction 6, 5

Subtypes of POTS

There are several subtypes of POTS, including:

• Neuropathic POTS, characterized by partial autonomic neuropathy 5
• Hypovolemic POTS, characterized by decreased blood volume 5
• Hyperadrenergic POTS, characterized by increased sympathetic activity and serum catecholamine levels 5, 4 Each subtype may require different treatment approaches, and accurate diagnosis is essential for effective management 5, 4