Written by Dimitrios Vrachatis, Specialist Cardiologist, PhD, National and Kapodistrian University of Athens.
What is ambulatory blood pressure monitoring (ABPM)?
The name Holter comes from the American physicist who invented prolonged heart rhythm monitoring, Norman J. Holter. His name has since become associated with prolonged recording of vital signs in ambulatory patients. It is therefore also used informally for prolonged blood pressure recording, known in English as ambulatory blood pressure monitoring (ABPM).
When is ABPM needed?
The cardiologist may request this examination to diagnose or rule out high blood pressure, or to monitor the effectiveness of treatment in patients already taking medication.
What are the advantages of ABPM?
Multiple blood pressure recordings over 24 hours, during both day and night, allow:
- More accurate measurements.
- Rapid, reliable diagnosis or exclusion of hypertension.
- Measurements during the person’s real-life activities.
- Identification of white-coat hypertension: elevated readings only when a healthcare professional is present.
- Identification of masked hypertension: high readings in everyday life but normal readings in the clinic.
- Assessment of day–night blood pressure patterns.
- Monitoring of medication effectiveness throughout the full 24 hours.
- Better prediction of hypertension-related damage to target organs.
What are the disadvantages?
If the examination is completed successfully and the recording is suitable for analysis — meaning that more than 70% of measurements are reliable — there are no particular disadvantages.
Some people may find frequent measurements uncomfortable, especially at night. Arrhythmias may affect the results; your doctor will be aware of this and take it into account. You cannot bathe or shower while wearing the device.
Why are night-time blood pressure recordings important?
Blood pressure normally falls by approximately 10–20% at night compared with daytime values.
Abnormal patterns, such as an excessive fall or, especially, an increase in blood pressure at night, are associated with higher cardiovascular risk.
How is ABPM performed?
The device consists of a cuff, similar to that on a conventional blood pressure monitor, and a small, lightweight central unit.
It automatically takes repeated measurements without intervention by the examiner or the person being examined, usually every 15 minutes during the day and every 30 minutes at night. Most devices use the oscillometric technique, as do most commercially available blood pressure monitors.
How is the device fitted?
The doctor places the cuff around the upper arm and positions the tube connecting it to the central unit comfortably. The unit is carried in a small pouch attached to a belt or suspended from a neck strap. Loose, comfortable clothes are advisable so the device does not bother you.
Do I need to prepare before ABPM?
No special preparation is required. As you cannot bathe or shower during the recording, it is advisable to do so before the appointment.
What should I do during ABPM?
You can follow your usual daily routine, including driving. Keep a brief diary of your activities during the examination so that any extreme readings can be interpreted.
When you feel the cuff inflate, stop what you are doing, straighten your elbow and wait for the measurement to finish. Make sure the tube connecting the cuff and the monitor is not kinked, so measurements can be taken correctly.
You cannot bathe or shower during the examination because the devices are not waterproof.
Are there any risks?
ABPM is non-invasive and does not carry risks, apart from the extremely rare possibility of local skin irritation caused by the cuff.
How are the results interpreted, and when will I receive them?
After the central unit has recorded the data, the doctor connects it to a computer and analyses the recording for extreme measurements and average blood pressure during the day, at night and over 24 hours. Results are provided immediately after processing with specialised software. Treatment decisions are made by the treating physician after considering the results alongside the person’s complete medical history.
What are normal ABPM values?
A 24-hour average blood pressure above 130/80 mmHg establishes a diagnosis of hypertension. The corresponding thresholds are 135/85 mmHg for daytime recordings and 120/70 mmHg for night-time recordings. The diagnostic threshold for clinic measurements is 140/90 mmHg, compared with 135/85 mmHg for measurements taken by the patient at home.