Tilt table test

# Overview
A tilt table test is a medical procedure often used to diagnose dysautonomia or syncope. Patients with symptoms of dizziness or lightheadedness, with or without a loss of consciousness (fainting), suspected to be associated with a drop in blood pressure are good candidates for this test.

# Concept behind the tilt test
The procedure tests for causes of syncope by attempting to cause syncope by having the patient lie flat on a special table or bed while connected to ECG and blood pressure monitors. The table then creates a change in posture from lying to standing.
A normal person's blood pressure will not drop dramatically while standing, because the body will compensate for this posture with a slight increase in heart rate and constriction of the blood vessels in the legs.
If this process does not function normally in the patient, the test could provoke minor symptoms to a very severe cardiac episode, depending on the person.

# Indications
- Recurrent episodes of syncope in the absence of organic heart disease.
- Recurrent episodes of syncope in the presence of organic heart disease after cardiac causes of syncope have been excluded.
- Unexplained single syncopal episode in high risk conditions (eg, occurrence or potential risk for physical injury or occupational hazard).
- When considered of clinical value to demonstrate patients susceptibility to vasovagal syncope.
- The test might also be considered in the following clinical setting.
To differentiate syncope with jerky movements found in epilepsy.
To evaluate patients with recurrent and unexplained falls.
In patients with psychiatric diseases with frequent syncopal episode.
- To differentiate syncope with jerky movements found in epilepsy.
- To evaluate patients with recurrent and unexplained falls.
- In patients with psychiatric diseases with frequent syncopal episode.

# Contraindications
Tilt test is contraindicated in the following patients:
- Absolute contraindications 
Orthostatic hypotension at baseline.
- Orthostatic hypotension at baseline.
- Relative contraindications 
Proximal coronary artery stenosis.
Critical mitral stenosis.
Clinically severe left ventricular outflow obstruction.
Severe cerebrovascular stenosis.
- Proximal coronary artery stenosis.
- Critical mitral stenosis.
- Clinically severe left ventricular outflow obstruction.
- Severe cerebrovascular stenosis.

# Preparations
Before actually taking the test, the patient may be instructed to fast for a period before the test will take place, and to go off of any medications he or she is taking. On the day of the tilt table test, a patient may be monitored using an electrocardiogram (ECG) while lying down. Some facilities insert an intravenous line in case the patient needs to be given medication quickly; however, this may influence the results of the test and may only be indicated in particular circumstances.

# Procedure
A variety of protocol have been described for the test that differ in the following way:
- In the angle of tilt (60 to 90o).
- In the duration of tilt (10 to 60 minutes).
- The administration of isoproterenol.

## Steps of the procedure
- A tilt table test can be done in different ways and can be modified for individual circumstances.
- In some cases, the patient will be strapped to a tilt table lying flat and then tilted or suspended completely or almost completely upright (as if standing).
- Most of the time, a patient is suspended at an angle of sixty to eighty degrees.
- In all cases, the patient is instructed not to move. Symptoms, blood pressure, pulse, electrocardiogram, and sometimes blood oxygen saturation are recorded.
Heart rate and symptoms are recorded every 3-5 mins.
ECG is continuously recorded.
Blood pressure can be recorded in 2 ways:
Beat to beat finger arterial monitoring.
Arm cuff every three to five minutes.
- Heart rate and symptoms are recorded every 3-5 mins.
- ECG is continuously recorded.
- Blood pressure can be recorded in 2 ways:
Beat to beat finger arterial monitoring.
Arm cuff every three to five minutes.
- Beat to beat finger arterial monitoring.
- Arm cuff every three to five minutes.
- Positive test findings are as follows:
Loss of consciousness/Fainting.
Significant fall in blood pressure or heart rate.
- Loss of consciousness/Fainting.
- Significant fall in blood pressure or heart rate.
- Patient is brought back to supine position if asymptomatic, even after 20 - 45 minutes.
- European society of cardiology recommends a passive phase (i.e. upright with no isoproterenol or nitroglyerin infusion).
- In patient remain asymptomatic, the patient is given Glyceryl trinitrate or isoproterenol, to create further susceptibility to the test.

## Isoproterenol infusion
- A second tilt test is done if patient remains asymptomatic during the above mentioned test.
- After infusion, patient is placed in the head-up tilt position for an additional 15 to 20 mins.
- Role in tilt test:  By activating 1-receptors on the heart, it induces positive chronotropic, dromotropic, and inotropic effects.
- Recommended dose: The infusion is usually titrated from 1 to 3 mcg/min to increase the heart rate by 20-25% above baseline.
- Special Note:
Controlled infusion should not be performed in patients with coronary artery disease, as it could lead to angina and serious arrhythmia.
Modest decrease in blood pressure with symptoms is common with isoproterenol infusion and is nonspecific.
- Controlled infusion should not be performed in patients with coronary artery disease, as it could lead to angina and serious arrhythmia.
- Modest decrease in blood pressure with symptoms is common with isoproterenol infusion and is nonspecific.

## Nitroglycerin infusion
- Role in tilt test: Nitrates cause venodilation with consequent reduction in venous return and stroke volume, without impeding the sympathetic response of increased heart rate and arterial vasoconstriction.
- Recommended dose: Fixed dose of 300-400 mcg of sublingual nitroglycerin administered in the upright position.
- Special Note:
Nitroglycerin increases the frequency of hemodynamic changes and reproduction of symptoms and may shorten test duration but increases the rate of false positive result.
- Nitroglycerin increases the frequency of hemodynamic changes and reproduction of symptoms and may shorten test duration but increases the rate of false positive result.

## Nitroglycerin vs Isoproterenol
- In a study comparing the two drug, rate of test positivity were similar (49% vs 41%) but sublingual nitroglycerin was found to be simpler to use, was better tolerated, and safer than low-dose isoproterenol.
- Another study showed that nitroglycerin had higher number of positive response than isoproterenol (55% vs 42%), especially among patients with positive tilt without any pharmacological agents.

# Test Results

## Symptoms
Typical symptoms of vasovagal or neurocardiogenic syncope includes:
- Nausea
- Sweatiness
- Pallor
- Lightheadedness
- Sensation of palpitations
- Near-fainting
- Fainting

## Test interpretation
Response to tilt table test can have various interpretation depending upon the clinical settings:
- In patients without structural heart diseases:
When reflex hypotension/bradycardia is induced with reproduction of spontaneous syncope  Diagnostic of Neurocardiogenic Syncope.
When reflex hypotension/bradycardia is induced without reproduction of syncope  Suggestive of Neurocardiogenic Syncope.
Development of slow progressive decrease in systolic blood pressure, with or without symptoms being induced  Diagnostic of Orthostatic hypotension syncope.
- When reflex hypotension/bradycardia is induced with reproduction of spontaneous syncope  Diagnostic of Neurocardiogenic Syncope.
- When reflex hypotension/bradycardia is induced without reproduction of syncope  Suggestive of Neurocardiogenic Syncope.
- Development of slow progressive decrease in systolic blood pressure, with or without symptoms being induced  Diagnostic of Orthostatic hypotension syncope.
- In patients with structural heart diseases:
Arrhythmias and other cardiac cause of syncope should be excluded before considering a syncopal episode as diagnostic of Neurocardiogenic Syncope.
- Arrhythmias and other cardiac cause of syncope should be excluded before considering a syncopal episode as diagnostic of Neurocardiogenic Syncope.
- Loss of consciousness without hypotension and/or bradycardia  Suggestive of Psychogenic pseudosynope
A tilt table test is considered positive if the patient experiences symptoms associated with a drop in blood pressure or cardiac arrhythmia.

## Consequences of the Test
- A common side effect during tilt table testing is a feeling of heaviness and warmth in the lower extremities. This is due to blood pooling in the legs and, to onlookers, the patient's lower extremities may appear blotchy, pink, or red.
- Dizziness or lightheadedness may also occur. Tilt table testing could provoke fainting or syncope as this is the purpose of the test and it may not be appropriate, or indeed possible to stop the test before this occurs as the drop in blood pressure or pulse rate associated with a faint can come on in seconds, This is why the patient's blood pressure and ECG should be continuously monitored during the test.
- In extreme, rare cases, tilt table testing could provoke seizures, or even prolonged asystole. If at any time in tilt table testing, a patient loses consciousness, he or she will be returned to a supine or head down position and will be given immediate medical attention, which could include being given fluids or perhaps atropine or adrenaline.