What is a tilt table test for patients with symptoms of orthostatic intolerance, such as fainting, dizziness, or lightheadedness, potentially related to postural orthostatic tachycardia syndrome (POTS), vasovagal syncope, or other cardiovascular and neurological disorders?

What is a Tilt Table Test?

A tilt table test is a diagnostic procedure that evaluates how your cardiovascular and autonomic nervous systems respond to postural changes by tilting you from a horizontal to an upright position (typically 60-70 degrees) while continuously monitoring blood pressure, heart rate, and symptoms to diagnose the cause of fainting, dizziness, or orthostatic intolerance. 1, 2

Purpose and Clinical Indications

The tilt table test serves three primary diagnostic goals 3:

• Assessing orthostatic hypotension (OH) - identifying abnormal blood pressure drops upon standing and distinguishing neurogenic from non-neurogenic causes 1, 4
• Evaluating chronic orthostatic intolerance - diagnosing conditions like postural orthostatic tachycardia syndrome (POTS) where symptoms occur without significant blood pressure drops 1
• Investigating unexplained syncope - reproducing vasovagal (reflex) syncope to confirm the diagnosis when the cause of fainting remains unclear 2, 5

The test is most valuable when cardiovascular causes have been reasonably excluded but neurally mediated syncope remains suspected, particularly in patients with recurrent episodes, occupational risk, or injury potential. 2

How the Test Works

Basic Protocol 2, 4

• Patient preparation: 4-hour fast prior to testing 2
• Pre-tilt stabilization: 5 minutes for nitroglycerine protocol, 20 minutes for isoproterenol protocol 2
• Tilt angle: 60-70 degrees (70 degrees for vasovagal syncope, 60 degrees for orthostatic hypotension assessment) 4
• Passive phase duration: 20 minutes before any pharmacological provocation 2
• Continuous monitoring: Beat-to-beat blood pressure and heart rate with ECG leads 6, 7

Pharmacological Provocation 2

The European Heart Journal recommends sublingual nitroglycerine (300-400 mg after 20 minutes passive tilt) as the preferred protocol because it provides similar sensitivity (61-69%) and specificity (92-94%) to isoproterenol without requiring IV access. 2

What the Test Diagnoses

Timing-Based Classification 1

The test differentiates conditions based on when symptoms occur after tilting:

• Initial orthostatic hypotension: 0-30 seconds - rapid blood pressure drop with quick recovery, common in young or elderly patients 1
• Classical orthostatic hypotension: 30 seconds to 3 minutes - sustained blood pressure decrease (≥20 mmHg systolic or ≥10 mmHg diastolic), often drug-induced or due to autonomic failure 1, 4
• Delayed orthostatic hypotension: 3-30 minutes - progressive blood pressure fall, frequently followed by syncope 1
• Vasovagal syncope: 3-45 minutes - sudden reflex-mediated blood pressure and heart rate drop with classic prodromal symptoms 1

Specific Diagnoses 1, 2

Postural Orthostatic Tachycardia Syndrome (POTS): Heart rate increase ≥40 bpm in adolescents (≥30 bpm in adults) or maximum heart rate >120 bpm within 10 minutes of standing, without significant blood pressure drop, accompanied by symptoms like lightheadedness, palpitations, tremor, weakness, blurred vision, and fatigue - notably, syncope is rare in POTS 1, 2

Vasovagal Syncope Types 1, 2:

• Vasodepressor type: Predominant hypotension from loss of vasoconstrictor tone
• Cardioinhibitory type: Predominant bradycardia or asystole (heart pauses)
• Mixed type: Both mechanisms present

Neurogenic vs. Non-neurogenic Orthostatic Hypotension 2, 3:

• Neurogenic OH shows blunted heart rate increase (<10 bpm) despite blood pressure drop
• Hypovolemic OH shows preserved or enhanced heart rate increase

Critical Interpretation Points

Essential Requirements 6, 5

The minimum requirements to perform tilt table testing are: a tilt table with appropriate tilt-down time, continuous beat-to-beat blood pressure monitor with at least three ECG leads, and trained staff familiar with protocols. 6

Diagnostic Validity 4, 6

An abnormal tilt table test result is most meaningful if the provoked event is recognized by patients or eyewitnesses as similar to spontaneous events - acknowledgement of reproducibility is mandatory in concluding a diagnosis. 4, 6

The test adds to history building but cannot replace it - findings must be interpreted in the context of the patient's clinical presentation 3, 6

Common Pitfalls to Avoid

• Don't ignore asymptomatic orthostatic hypotension: Symptoms depend more on absolute blood pressure level than magnitude of fall, and cerebral autoregulation plays a key role 4
• Don't use the test to assess treatment response: Tilt table testing is not useful for monitoring therapeutic efficacy 5
• Don't skip the initial active standing test: A simple bedside active standing test using a sphygmomanometer (measuring blood pressure supine and during 3 minutes of standing) should be performed before proceeding to formal tilt table testing 2

Clinical Significance

Delayed orthostatic hypotension carries significant prognostic implications: 54% of individuals progress to classic orthostatic hypotension over 10 years, with a 10-year mortality rate of 29%. 4 This underscores the importance of proper diagnosis and follow-up.

The test can also serve therapeutic purposes by educating patients on recognizing prodromes and performing physical countermaneuvers for syncope prevention (biofeedback) 6