Tilt Table Test.
A Tilt Table Test is performed in a quiet warm room specially equipped for the investigation. The individual lies flat on a tilt table and is attached to real-time ECG and blood pressure monitoring equipment. After a short period of rest the table is tilted (head up) to 70° and maintained at that angle for 40 minutes or until typical symptoms occur. 50% to 60 % of patients with unexplained syncope reproduce their symptoms at around 20 minutes, often with associated dramatic slowing of the heart rate or even ventricular standstill – see NCS bradycardia and NCS asystole – and precipitous lowering of the blood pressure – see graphs.
The exact pattern of the heart rate and blood pressure change can help determine the best line of treatment. Removing the tilt restores the heart rate and blood pressure to normal and quickly abolishes symptoms. The sensitivity of the test may be increased by administering Glyceryl Trinitrate 400 micrograms (Nitrolingual Spray ) 20 minutes into the test, continuing for another 20 minutes or until typical symptoms/syncope occur.
Currently trials are testing the specificity and sensitivity of Glyceryl Trinitrate 800 micrograms administrated 10 minutes before tilting, followed by tilting at 70° for 20 minutes or until typical symptoms/syncope occur.
Induced syncope is much more common when Glyceryl Trinitrate is used. It is therefore essential to demonstrate slowing of the heart rate at the point of syncope before concluding that the collapse is due to Autonomic Mediated (Neurocardiogenic) syncope.
Glyceryl Trinitrate should not be used in Aortic Stenosis, HOCM, Mitral Stenosis, Constrictive Pericarditis, Pulmonary Hypertension, Anaemia or Hypovolaemia.
Indications for Tilt Table Testing – and (strength of recommendation)
- Recurrent syncope in absence of heart disease or in the presence of heart disease once cardiac causes of syncope have been excluded.
- Unexplained single episode in high risk setting, e.g. occurrence of, or a potential risk for, physical injury or with occupational implications.
Not so strong:
- Recurrent pre-syncope or dizziness.
- Recurrent unexplained falls.
- For differentiating syncope with jerking movements from epilepsy.
- Single episode without injury and not in high risk setting.
- Clear cut clinical vasovagal features leading to a diagnosis when the demonstration of neurally mediated syncope would not alter treatment.
Diagnosis – and (strength of recommendation)
- In patients without structural heart disease the investigation can be considered diagnostic when syncope is reproduced.
- In patients with structural heart disease arrhythmias or other cardiac causes should be excluded prior to considering a positive result as evidence for neurally mediated syncope.
Not so strong:
- The clinical meaning of abnormal responses other than induction of syncope is unclear.