What is head up tilt test (HUTT) – Cardiology Basics


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What is head up tilt test (HUTT) – Cardiology Basics

Head up tilt test, known as HUTT or tilt table test is commonly done for the evaluation of recurrent episodes of syncope with no other evident cause. Change in heart rate and blood pressure on assuming the erect posture is monitored in this test. It is also useful in the evaluation of postural orthostatic tachycardia syndrome (POTS), a condition in which the heart rate increases on standing up. Various protocols are followed in different centres for HUTT.

One protocol is as follows: The subject is strapped to the tilt table and heart rate and blood pressure monitors connected. Ideally a beat-to-beat finger blood pressure monitoring device is to be used, though it is not available always and is more expensive than the usual blood pressure monitoring equipment. Usual blood pressure monitoring equipment cannot provide a beat-to-beat change in blood pressure and may be difficult to use during a syncopal episode.

Infusion pump for delivering medications is set up in the beginning, to be used if needed. ECG, oxygen saturation measured by pulse oximetry and blood pressure are charted at regular intervals during the test. Resuscitation tray and personnel are at hand during the test.

In the first phase of the test, the person lies in the supine position for 30 minutes. This is followed by a tilt phase of 20 minutes at an angle of 70 degrees. If fainting does not occur during the period, the tilt table is brought to the horizontal position for 10 minutes.

After that, isoprenaline infusion, which can increase the heart rate and myocardial contractility, is infused at the starting dose and the drip is run for 10 minutes, with the table tilted to 80 degrees. Still if syncope does not occur within 10 minutes, the table is brought back to the horizontal position for 10 minutes.
The test is repeated at two higher doses of isoprenaline with intervening 10 minutes in the horizontal position, if needed. If no syncope occurs even with the higher doses of isoprenaline, the test is considered negative.

Syncope can occur at any of the above stages with either bradycardia, hypotension or both. The first response is called cardioinhibitory, second as vasodepressor and third as mixed variety. Strapping of the person to the table prevents a fall and injury if the person faints. There are some experts who feel that head up tilt test is not useful and should be abolished!

A change in the pattern of HUTT response with age has been described, with cardioinhibitory 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 recurrent, 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