Introduction
This booklet has been written by the Autonomic Unit at The National Hospital for Neurology and Neurosurgery (NHNN). The aim of the booklet is to provide information about the autonomic function test (AFT).
It is intended for use by patients (or their families or carers) who have been referred to our service for an AFT. If you have any questions about this, a member of the Autonomic team will be happy to answer them for you.
The autonomic nervous system (ANS) is an important mechanism that controls all the bodily functions that are under unconscious control. This includes things like heart rate (HR), blood pressure (BP), temperature control, the bladder, digestion and bowel movements.
When one or more parts of this system are impaired, it can result in a variety of disorders. In the Autonomic Unit, we focus on testing how well the ANS is functioning in a patient, using various tests, to be able to diagnose these conditions.
The AFT is a specific clinical test that is used to diagnose disorders related to abnormalities regarding the ANS. The AFT focuses on the cardiovascular system and more specifically, BP and HR, to provide a measure of autonomic function. The test measures a patient’s ability to alter their blood pressure and heart in response to certain challenges. This test helps your consultant to diagnose various autonomic dysfunction conditions or plan and carry out treatments.
An AFT is a useful diagnostic test, although any clinical benefit should always outweigh the possible risks associated with the procedure.
During an AFT we are trying to provoke symptoms that you try to avoid in everyday life by challenging the ANS in various ways. The clinical autonomic scientist (CAS) performing your test will make it clear that as the patient you are always in control and you can decline to do any part of the test should you wish to.
During head-up tilt there may be marked falls in BP, increases in HR or spontaneous falls in BP and/or HR which will require the CAS to return you to lying flat.
The equipment we use may cause mild damage to the integrity of the skin. This includes the BP cuff squeezing uncomfortably tight, causing irritation to the skin, a slight redness from the sticky pads if you have sensitive skin and light bruising at the site of the needle insertion.
The decision to have an AFT is entirely yours. Declining this procedure will not affect our attitude towards you or influence any other aspect of your care. It may mean, however, that your consultant cannot be as certain or specific about any future treatment or diagnosis.
Your consultant or clinical nurse specialist (CNS) will have taken into account the potential risks and benefits of having an AFT during your initial referral.
If you feel uncomfortable about any part of the test you are able to decline doing it and the CAS will modify the test accordingly.
Please do not eat four hours prior to testing; you may drink water only.
Please ensure your hands are kept warm in preparation of this test.
Please bring a list of your medications with you.
It is advisable to bring a bottle of water with you to help re-hydrate after testing.
You may need to stop certain medications prior to testing, although the consultant or CNS should be able to advise you during your initial consultation; if you are unsure, please call us directly or ask us when you confirm your appointment.
If you are not able to lie still on your back for prolonged periods, please inform us.
If you are pregnant/become pregnant before your appointment your test will have to be postponed.
We want to involve you in all the decisions about your care and treatment. If you decide to go ahead with treatment, by law we must ask for your consent. This confirms that you agree to have the procedure and understand what it involves, which may include video recording the procedure; only those persons involved in your care will be able to view the video.
If you are unsure about any aspect of your proposed treatment, please do not hesitate to speak with a senior member of staff again.
The testing procedure
There are three parts to an AFT; the consultant will make the decision which parts each patient requires.
Screening autonomic function test
The CAS will firstly talk through your history relating to your presenting autonomic symptoms that you will have previously described to the consultant and your GP and the test will be explained in detail. The CAS will ask for your height and weight and ask you to remove your shoes and socks.
You will be asked to lie down on your back on a bed where you will rest for approximately 10 minutes while some BP and HR recordings are taken from a cuff we attach to your upper arm. You will then be asked to do a five-minute stand by the side of the bed.
The CAS will then attach the rest of the equipment while you are lying down. This includes:
A three-lead electrocardiogram (ECG) to measure your heart rhythm – you will have a sticky pad placed either side of your chest and one on your ankle. We will clean these three areas prior with an alcohol wipe.
A cuff that sits on your finger attached to a device on your wrist which measures your BP and HR continuously.
A respiratory belt round your middle to measure your breathing pattern.
The CAS will then ask you to perform various activities which include things like breathing challenges and a hand grip challenge while keeping a close eye on your blood pressure and heart rate. None of these are particularly difficult although you have to work hard at them.
After these exercises, the CAS will strap you in safely to the bed. The bed will then be raised up and forward until you are standing head up at a 60o angle as demonstrated in the second picture shown below. This tilt test will be for 10 minutes or as long as you can tolerate while the CAS keep a close eye on your blood pressure and heart rate. You will be encouraged to report any symptoms you experience.
This screening AFT will take around 90 minutes.
The AFT testing room and equipment setup:
Head up tilt at 60°:
Plasma Catecholamine Levels
If a blood test is required the CAS will put a special needle (a cannula) in your arm during the AFT, just before the tilt test. Blood samples will be taken at two points during the test – one lying down flat and one upright on the tilt, each after 10 minutes of rest. The needle will be removed before you leave.
Your blood samples will be analysed for levels of plasma adrenaline and noradrenaline, comparing the samples while lying down and while upright.
Prolonged Tilt
Your blood pressure and heart rate will be monitored while you are tilted head up at 60° for a maximum of 45 minutes, or for as long as you can tolerate. You will be encouraged to report any symptoms you experience.
We will always make sure you feel well enough to leave the testing room after your test has finished.
Once you have completed all of your clinical tests with us, the results will be analysed and discussed at a multi-disciplinary team (MDT) meeting.
A brief summary letter will then be sent to you and your referring doctor (normally your GP) detailing the results of your tests.
You will then have a follow-up appointment with a consultant or a CNS to explain the results in more detail, and to also answer any questions you may have.
You may find the following websites useful: www.
UCLH cannot accept responsibility for information provided by other organisations.
Address:
National Hospital of Neurology and Neurosurgery, The Autonomic Unit
2nd Floor Queen Mary Wing
Queen Square
London
WC1N 3BG
Direct tel: 0203 448 3079
Switchboard: 0203 456 7890
Fax: 0203 448 3878
Email: uclh.enquiry.autonomic.secretaries@
Website: www.
The Autonomic Unit is located on the second floor of the Queen Mary Wing at the National Hospital for Neurology & Neurosurgery, Queen Square.
Please follow signs from the main entrance towards the Queen Mary Wing and you should find the appropriate set of lifts/stairs on your right hand side. Head to the second floor and use the intercom to contact our admin team who will let you in once you have confirmed your identity.
