What is an Ambulatory Blood Pressure Monitor (ABPM)?
Blood pressure is characterized by a clear circadian rhythm, the natural 24-hour rhythm set by the body's "biological clock." Blood pressure normally rises in the early morning, varies during the day depending on activity and falls during sleep.
While blood pressure readings taken occasionally by the GP may be able to signal a problem, an Ambulatory Blood Pressure Monitor (ABPM) provides a more comprehensive picture of actual blood pressure status. It's also a better predictor of damage and heart problems caused by high blood pressure than standard blood pressure test. This means you and your cardiologist have solid information to rely on when considering treatment options.
A blood pressure (BP) machine is fitted for a 24-hour period and measures your blood pressure, rather than a single measurement of blood pressure with your doctor. This gives a better indication of your blood pressure while you go about your daily activities, including sleeping and rest periods.
Please consult with your doctor regarding whether or not an ABPM is appropriate for you. It is often recommended for:
- individuals whose home BP is significantly lower than their clinic or office BP (> 10-15 mmHg difference)
- individuals whose BP is difficult to control on multiple blood pressure lowering drugs
- individuals who have symptoms suggesting low BP on treatment for high blood pressure
- patients who have a history of heart disease and develop symptoms suggesting high BP during those symptoms (e.g., heart failure, headaches, dizziness, etc).
Blood pressure is measured either by the sounds using a microphone under the blood pressure cuff (ausculatory method - similar to the way your doctor uses a stethoscope to measure your blood pressure in the surgery), or using sophisticated electronics to measure the movement of the blood after compression of the artery at the elbow (oscillometric method). Some devices use both methods. The data is stored on the portable device, and then interpreted by trained professionals in your doctor's office.
The monitor is a small device worn in a pouch that has a blood pressure cuff attached to it. The cuff is fitted on the patients arm and inflates and deflates automatically throughout the 24- or 48-hour period it is worn.
Wearing a monitor doesn't interfere with daily activities. The monitors are lightweight, comfortable to wear and quiet. Staff in your cardiologist's office will program the device to automatically measure your blood pressure throughout the day and night. You will have an inflatable cuff worn on one arm and a recording device about the size of a Sony Walkman worn at the waist.
In addition to wearing the monitor, your cardiologist may ask you to keep a diary about what time you wake up or go to sleep, when you eat meals, experience strong emotions, stress, take medication, exercise or have other experiences that can affect your blood pressure.
ABPM is now a routine procedure in the UK and it is being used increasingly to evaluate hypertension and related conditions such as:
"White Coat" Hypertension - This means that you only have high blood pressure when you are in the doctor's office. Studies suggest that more than 20 percent of patients identified as having high blood pressure are misdiagnosed because they have "White Coat" hypertension. People with "White Coat" hypertension may be prescribed drug therapy that can be expensive and have side effects. ABPM takes away the guesswork and gives a more realistic picture of blood pressure. It can help doctors solve the diagnostic problem that "White Coat hypertension" presents.
"White Coat" Normotension - About five percent of the population has "White Coat" normotension. This means that your blood pressure is lower when it's being taken in the doctor's office, but rises when you leave. Ambulatory Blood Pressure Monitoring can alert your doctor to the true state of your blood pressure if you have "White Coat" normotension.
Resistant Hypertension - This is diagnosed when several medications fail to control high blood pressure as measured in the doctor's clinic or office. The office reading may not be representative of your blood pressure over the course of a day. It depends, in part, on the time your blood pressure is measured in relation to the time your medications are taken. ABPM will show the degree and duration of medication action in your body. This will give your doctor valuable information to target your medications especially for you.
Borderline Hypertension - Sometimes people have high normal blood pressure readings (a diastolic or bottom number of 85 to 89 mmHg) in the doctor's office. But, a closer look reveals that there is damage to the heart, kidneys or eyes because of the high blood pressure. ABPM can show higher readings outside of the doctor's office in association with physical activity, for example, or work-related stress. This may mean that casual measurements of your blood pressure in your doctor's office have underestimated the degree of hypertension.
Episodic Hypertension - ABPM can help detect periodic high blood pressure that indicates another medical problem. ABPM can also help detect high blood pressure associated with some anxiety syndromes.
Hypertension during Pregnancy - If you have chronic hypertension and become pregnant, your doctor may want to gather more comprehensive information about your blood pressure and may prescribe ABPM. If you're showing signs of eclampsia, a kind of high blood pressure that appears after the 20th week of pregnancy in some people, ABPM may be appropriate.