Proper Protocol for Performing a Tilt Table Test
The standard protocol for tilt table testing involves fasting for 2-4 hours before the test, a supine pre-tilt phase of 5-20 minutes, tilting at an angle of 60-70 degrees for 20-45 minutes, with optional pharmacological provocation using nitroglycerin or isoproterenol if the passive phase is negative. 1
Patient Preparation
- Patient should fast for 2-4 hours before the test
- The room should be quiet with dim lighting
- Explain the procedure to the patient to reduce anxiety
- Secure the patient to a motorized tilt table with foot support
Equipment Requirements
- Tilt table with foot-board support and quick tilt-down capability (<15 seconds)
- Continuous beat-to-beat blood pressure monitoring (non-invasive preferred)
- ECG monitoring with at least three leads
- Trained staff present throughout the procedure with physician immediately available
Testing Protocol
Pre-Tilt Phase
- Position patient supine on the tilt table
- Monitor for 5 minutes if no venous cannulation is performed
- Monitor for 20 minutes if venous cannulation is performed 1
Passive Tilt Phase
- Tilt table to 60-70 degrees
- Maintain this position for 20-45 minutes (minimum 20 minutes recommended)
- Monitor blood pressure, heart rate, and symptoms continuously
- Return to supine position if syncope occurs or upon completion of the passive phase
Provocation Phase (if passive phase is negative)
Option 1: Nitroglycerin Protocol
- Administer 300-400 μg sublingual nitroglycerin while patient remains upright
- Continue monitoring for 15-20 minutes
- This is preferred when venous access is not established (Italian protocol) 1
Option 2: Isoproterenol Protocol
- Administer incremental infusion from 1-3 μg/min
- Target heart rate increase of 20-25% above baseline
- Continue monitoring for 15-20 minutes
- Contraindicated in ischemic heart disease, uncontrolled hypertension, LVOT obstruction, and significant aortic stenosis 1
Response Classification
A positive test is defined as induction of presyncope or syncope associated with hypotension, with or without bradycardia. Responses are classified as:
Vasovagal (reflex) syncope:
- Type 1 (Mixed): Heart rate falls but not below 40 bpm or below 40 bpm for less than 10 seconds
- Type 2A (Cardioinhibitory without asystole): Heart rate falls below 40 bpm for more than 10 seconds
- Type 2B (Cardioinhibitory with asystole): Asystole occurs for more than 3 seconds
- Type 3 (Vasodepressor): Heart rate does not fall more than 10% from peak at time of syncope 1
Orthostatic Hypotension:
POTS: Heart rate increase ≥30 bpm (or max HR ≥120 bpm) within 10 minutes without profound hypotension 3
Interpretation and Documentation
- Document the time to symptom onset
- Record the hemodynamic changes (blood pressure and heart rate)
- Note whether symptoms reproduced match the patient's typical episodes
- Confirm with patient/witness that the induced attack resembles their typical episodes 4
Safety Considerations
- Tilt-down time should be short (<15 seconds) to minimize consequences of prolonged loss of consciousness
- Have resuscitation equipment readily available
- Minor side effects are common (palpitations with isoproterenol, headache with nitroglycerin)
- Atrial fibrillation may occur during or after a positive test but is usually self-limited 1
Common Pitfalls to Avoid
- Failure to correlate tilt-table findings with the patient's clinical presentation can lead to false-positive interpretations 1
- Invasive blood pressure measurements may affect test specificity, especially in elderly and children 1
- Omitting extended monitoring beyond 3 minutes may miss delayed orthostatic hypotension, which occurs in approximately 39% of patients only after 10 minutes of tilt 2
- Misinterpreting convulsive movements during syncope as epileptic seizures 5
The tilt table test is a valuable diagnostic tool that complements clinical history but cannot replace it. Proper execution of the protocol and careful interpretation of results are essential for accurate diagnosis of syncope and related disorders.