Head Up Tilt Test (HUTT)

Transcript of the video: Head up tilt test, is usually done for the evaluation of recurrent syncope. Sometimes, head up tilt test, also known in short as HUTT, is also done for the evaluation of postural orthostatic tachycardia syndrome, POTS, a condition in which there is tachycardia on standing up, without a fall in blood pressure. In usual syncope, there could be a fall in blood pressure, bradycardia, and there are various types, which will be described.

There are various protocols for head up tilt test, which are followed in different institutions. Basically you need a tilt-table, in which the person is lying down first and observed for some time and then a tilt is given. Usually, the initial tilt given is 70 degrees. So, in case of syncope, this person can fall off. To prevent that, the person is strapped on to the tilt table before the onset of the test. And the basic principle is to observe the heart rate and blood pressure during the procedure. Ideally, a beat to beat pressure has to be monitored using a finger blood pressure or invasive blood pressure monitoring. Finger blood pressure monitoring is costly and invasive blood pressure is an invasive procedure is invasive, and not ideal in a person with syncope who can develop syncope with the procedure itself! So, there are various protocols. And sometimes, challenge with nitroglycerine or isoprenaline may be needed to induce syncope, if syncope doesn’t occur during the tilt table test without medications.

If syncope does not occur with 70 degrees tilt, it can be done at 80 degrees tilt. But, each time the protocol is changed, the person is brought down to the supine position for the heart rate and blood pressure to become normal and then only the second protocol is followed, whether it is the drug challenge or change in the inclination. Various types of responses can occur to head up tilt test. The most common is mixed type, in which, in the tilted position, the person develops both bradycardia and hypotension and usually there is a syncope. Fall is prevented by the strapping. That is the mixed type, which is the commonest and asystole may occur, more than 3 seconds. And whenever there is syncope, the person is immediately brought back to the supine position. Otherwise it is likely to cause more of hemodynamic stress. Second is cardioinhibitory response, in which there is bradycardia, but no hypotension. And the third is vasodepressor response, in which there is no bradycardia, but there is hypotension. These are the different types of responses which can occur in HUTT.

A change in the pattern of HUTT with age has been described, with cardioinhibtory response becoming less common with advancing age. This difference is thought to be due to the higher vagal activity in younger age, promoting more of cardioinhibitory responses.

Indications for HUTT in syncope include:

1. Recurrent syncope or presyncope
2. High risk patients with single syncopal episode: e.g. Serious injury with syncope, syncope while driving
3. No other cause for symptoms by history, examination, or cardiovascular and neurological workup.
4. Elderly patients with recurent, unexplained falls.
5. For the differential diagnosis of: Convulsive syncope, Orthostatic hypotension, Postural orthostatic tachycardia syndrome, Psychogenic syncope, Hyperventilation syncope, Carotid sinus hypersensitivity.

Relative contraindications for HUTT include:

1. Severe left ventricular outflow obstruction
2. Critical mitral stenosis
3. Severe proximal coronary artery disease
4. Severe cerebrovascular disease