24-hour ambulatory blood pressure monitoring (ABPM)
Ambulatory Blood Pressure Monitoring (ABPM) involves recording of your blood pressure as you move around and living your normal daily life. It is normally performed over a period of 24 hours. It uses a small digital blood pressure machine that is attached to a belt around your body and which is connected to a cuff around your upper arm. The monitor is small enough to carry while you can go about your normal daily life and even sleep with it on.
Why might I need a 24-hour monitor?
By measuring your blood pressure at regular intervals over 24 hours, your doctor is able to get clear pictures of how your blood pressure changes throughout the day. There are a number of reasons why your doctor might suggest this test:
- They may want to find out if your high blood pressure readings in the clinic are much higher than they are away from the clinic (called the “white coat effect”).
- They may want to see how well your medicines are working, to make sure they are controlling your blood pressure through the day.
- They may want to see if your blood pressure stays high at night. If this is the case, they may need to change or adjust your medicines.
What happens during 24-hour blood pressure monitoring?
A 24-hour blood pressure measurement is just the same as a normal blood pressure check: a digital machine takes your blood pressure by inflating a cuff around your upper arm and then slowly releasing the pressure. The machine is small enough to be worn on a belt on your waist while the cuff stays on your upper arm for the full 24 hours.
The machine then takes blood pressure readings at regular intervals throughout the day: usually, every 15-30 minutes during the daytime and 30-60 minutes at night. You will need to keep the monitor on through the night – you could put the machine under the pillow or on the bed while you sleep.
Because the test is being carried out to find out what your normal daily blood pressure is, it is important to carry on with your normal routine activities and do all the things you would normally do. The only things you should avoid doing for the day are swimming and having a bath or shower.
At the end of the 24 hours you can remove the machine and cuff and give it back to the clinic. The machine will have stored all your readings and these will then be analysed on a computer.
What do I need to do during 24-hour blood pressure monitoring?
To allow the machine to work properly, it is important to make sure that the tube to the machine is not twisted or bent. Also, just before the machine is about to take a reading, it will beep. When this happens you should:
- Relax and sit down and, if possible
- keep the cuff at the same level as your heart
- keep your arm steady.
You will also be asked to keep a diary of what you were doing just before the reading was taken, what time you went bed and got up and if and when you took medications. Some people find 24-hour ABPM distracting and uncomfortable: if you feel like this when the readings are being taken, speak to us doctor as it may affect your reading.
White coat hypertension (and white coat effect)
The term “white coat” comes from references to the white coats traditionally worn by doctors. The white coat effect means that your blood pressure is higher when it is taken in a medical setting than it is when taken at home. On average, when your blood pressure is taken at home the top (systolic) number can be around 10mmHg lower than it would be if taken by a doctor and 5mmHg lower on the bottom (diastolic) number. For some people this difference can be even greater.
What causes the white coat effect?
Your blood pressure is not fixed – it rises and falls throughout the day in response to what you are doing and what is happening around you. White coat effects will often happen because you are nervous about having your blood pressure tested by a doctor or nurse. Most of us tend to feel more tense in medical settings than we do in surroundings that are familiar to us, although we do not always notice it.
The white coat effect can influence some peoples’ blood pressure more than others. If you are very anxious your systolic blood pressure can rise by as much as 30mmHg. This can make it more difficult for your doctor to get an accurate measurement of your blood pressure.
What is white coat hypertension?
The term white coat hypertension may be used if you have high blood pressure readings (i.e. readings that are consistently 140/90mmHg or above) only when you are in a medical setting. Your blood pressure readings may be normal when they are taken at home.
Sometimes it can be difficult to establish whether you actually have high blood pressure, or are just experiencing white coat hypertension.
How will I know if my blood pressure is affected?
Anyone can be affected by the white coat effect, but white coat hypertension is less common. You may be nervous or anxious about having your blood pressure taken without you or your doctor realising it. The only way to be sure is to compare readings taken in the clinic with readings that are taken at home. There are two ways of doing this.
- Measuring your blood pressure at home – You could measure your blood pressure at home. Measuring your own blood pressure regularly can be helpful as it allows your doctor or nurse to see what your readings are like outside of the clinic. Keeping a personal record of your blood pressure can help to show what your blood pressure is like from day to day
- 24-hour blood pressure monitoring – This kind of blood pressure monitoring can show in more detail how your blood pressure changes throughout the day. You will be given a small digital monitor to wear which measures your blood pressure regularly and automatically over a day and night. Your readings are stored in its memory so you don’t need to do anything apart from keeping the monitor on. Some GP surgeries can provide 24-hour monitors; alternatively you may have to go to your local hospital outpatients department to have one fitted.
What can I do about white coat hypertension?
If you are experiencing white coat effects when having your blood pressure measured, it is important to try and manage your anxiety if you can. This might just mean resting for a while before having your blood pressure measured. If you have had to rush to your appointment or are feeling nervous, taking a moment to relax and calm down can help to bring your blood pressure back down to normal.
Sometimes it may not be possible to overcome the white coat effect. In this case your doctor will discuss options with you. To gain a clearer picture of your blood pressure your doctor may ask to see home blood pressure readings or decide to monitor you more closely for a period of time.
I have been diagnosed with high blood pressure, but could it be white coat hypertension?
Your doctor or nurse will be aware of white coat hypertension and will take it into consideration before making any diagnosis about your blood pressure.
People with white coat hypertension can go on to develop high blood pressure. For this reason it is important to have your blood pressure checked regularly (perhaps every 6-12 months with a medical professional). This will allow you to take appropriate steps to lower your blood pressure, should it start to rise.
If you have any queries or concerns about the white coat effect or white coat hypertension, speak with your doctor or nurse.
Blood tests and high blood pressure
A blood test is a quick and simple way to measure the amount of certain proteins, minerals, fats and sugars in your blood. By looking at the levels of these in your blood, your doctor can find out how well your body is working and whether or not you have certain conditions or health problems.
When you are first diagnosed with high blood pressure, your doctor or nurse may carry out one or more blood tests to help them plan the best treatment for you. This will show them:
- if you have a raised cholesterol level
- if you have another medical problem, such as a kidney condition or diabetes
- whether or not you have a problem with your adrenal glands or kidneys
- which medicines might work best for you.
How is a blood test carried out?
Blood tests are very common and taking blood is a simple procedure. It can usually be carried out at your local surgery by your doctor or nurse.
If your doctor or nurse only needs to know your blood sugar levels (for example when looking for diabetes), then just a small prick on the tip of a finger is needed to release a few drops of blood.
However, most tests normally require a test tube of blood, which will need to be collected by a syringe. If needles make you feel uncomfortable, speak to your doctor or nurse. They will be able to help.
Since no anaesthetics or special procedures are needed, you will be able to leave the surgery straightaway and carry on with your day as normal. If you feel faint while the blood is being taken, you may be asked to rest for a while afterwards.
Do I need to do anything before the test?
Depending on what your doctor or nurse is testing for, you might be asked to avoid eating anything for a period before the test. For example, if they want to look at your blood sugar levels, they may ask you to come in first thing in the morning, before having breakfast.
How soon will I know the results?
Your blood sample will need to be sent to a laboratory for testing, and the results will then be analysed by your doctor. This can take up to a few weeks.
Echocardiogram and high blood pressure
An echocardiogram is a scan which gives a detailed view of the structures of your heart, and which can show how well your heart is working. The scan uses a probe that sends out sound waves, which are reflected back by the muscles and tissues in your heart. These reflected waves are picked up by the probe and translated into images on a screen.
Echocardiograms can show if your heart is working as well as it should. They are particularly useful for revealing if you have an enlarged left side of the heart, or problems with your heart valves. They can also be used to investigate the causes and effects of heart murmurs and heart attacks.
How is an echocardiogram carried out?
An echocardiogram is a painless test that takes roughly 30-45 minutes. It can be carried out in one of two ways.
If your doctor is looking for an enlarged heart muscle or heart valve problems, the probe is normally placed on your chest. Lubricating jelly will be put on your chest and a small probe will be moved around on your chest. Moving the probe around will give different views of your heart.
If your doctor is looking for more detailed information about how your heart is working, a small probe will be passed down your throat so that it lies behind your heart. This means that your doctor will have a much clearer view, as your heart and ribcage will not be in the way. You will receive a sedative and/or local anaesthetic for this procedure, but it should not require an overnight stay in hospital.
What do I need to to before an echocardiogram?
If the probe is going to be placed on your chest, you do not need to do anything beforehand.
If the probe is going to be passed down your throat, you will be asked not to eat anything for a few hours before the test because you will be given a sedative. Also, you will be asked not to drive for 24 hours after the test because you may still be slightly sleepy.
For both tests you should continue to take your blood pressure medicines and any other medicines as normal.