On this page
- What is this?
- What does ambulatory blood pressure monitoring involve?
- What are the uses of ambulatory blood pressure monitoring?
- Who should be referred for ambulatory blood pressure monitoring?
- Upper limit of normal ambulatory blood pressure monitoring values
- Downside to ambulatory blood pressure monitoring
- How are the results of ambulatory blood pressure monitoring provided?
- Dippers and non-dippers
- Document references
- Acknowledgements
What is this?
Ambulatory blood pressure monitoring (ABPM) is a noninvasive method of obtaining blood pressure readings over twenty-four hours, whilst the patient is in their own environment, representing a true reflection of their blood pressure.
Many studies have now confirmed that blood pressure measured over a 24-hour period is superior to clinic blood pressure in predicting future cardiovascular events and target organ damage.1,2
What does ambulatory blood pressure monitoring involve?
Blood pressure is measured over twenty-four hours using auscultatory or oscillometry and requires use of a cuff. The monitor takes blood pressures every 20 minutes (less frequently overnight, e.g. 1-hourly).
What are the uses of ambulatory blood pressure monitoring?
- To obtain a twenty-four hour record - more reliable than one-off measurements. Studies have shown that increased blood pressure readings on ABPM are more strongly correlated to end-organ damage than one-off measurements, e.g. left ventricular hypertrophy.3,4
- To detect white coat hypertension.
- It has use in hypertension research, e.g. reviewing 24-hour profile of antihypertensive medication.
- It may have prognostic use - higher readings on ABPM are associated with increased mortality.5
- Response to treatment.2
- Masked hypertension.2
- Episodic dysfunction.2
- Autonomic dysfunction.2
- Hypotensive symptoms whilst on antihypertensive medications.2
- It may be more cost-effective in the long-term.
Who should be referred for ambulatory blood pressure monitoring?
- Any patient with persistently raised blood pressure readings or labile blood pressure should be considered for ABPM (whether or not on treatment). However, it is not a screening tool.
- Borderline readings in clinic.
- Poorly controlled hypertension, e.g. suspected drug resistance.
- Patients who have developed target organ damage despite control of blood pressure.
- Patients who develop hypertension during pregnancy.
- High-risk patients, e.g. those with diabetes mellitus, those with cerebrovascular disease and renal transplant recipients.6,7
- Suspicion of white coat hypertension - high blood pressure readings in clinic which are normal at home.
- Suspicion of reversed white coat hypertension, i.e. blood pressure readings are normal in clinic but raised in the patient's own environment.
- Postural hypotension.
- Elderly patients with systolic hypertension.8
Upper limit of normal ambulatory blood pressure monitoring values
Normal ambulatory BP during the day is <135/<85 and <120/<70 at night.
Levels above 140/90 during the day, and 125/75 at night should be considered as abnormal.2
Downside to ambulatory blood pressure monitoring
- It is not widely available although this is improving.
- It requires specialist training.
- Some patients find inflation of the cuff unbearable.
- Sleep disturbance.
- Bruising where the cuff is located.
- Background noise may lead to interference (less with oscillometric methods).
- Poor technique and arrhythmias may cause poor readings.9
How are the results of ambulatory blood pressure monitoring provided?
- This varies according to the machines used.
- Night-time mean, daytime mean and overall mean are also provided.
- Usually, they have individual systolic and diastolic pressures. These may also be represented in a graphic form.
- Blood pressure load - the percentage or proportion of readings that are higher than a predetermined level in twenty-four hours.
- There are lots of other analyses that are possible - they have varied uses.
- Day and night blood pressure: there is some evidence that night-time blood pressure gives crucial information, such as higher night-time readings being more associated with risk of developing target end-organ damage.
Dippers and non-dippers
- Blood pressure will fall at night in normotensive individuals.
- In hypertensive patients the blood pressure may fall excessively at night (>10%), leading to describing patients as 'dippers', which is associated with a poor outcome.3,6
- In 'non-dippers' the blood pressure remains high, i.e. less than 10% lower than daytime average. This has also been reported to be associated with a poor outcome.
Document references
- White WB; Importance of aggressive blood pressure lowering when it may matter most. Am J Cardiol. 2007 Aug 6;100(3A):10J-16J. Epub 2007 May 25. [abstract]
- Wexler R; Ambulatory blood pressure monitoring in primary care. South Med J. 2010 May;103(5):447-52. [abstract]
- Clement DL, De Buyzere ML, De Bacquer DA, et al; Prognostic value of ambulatory blood-pressure recordings in patients with treated hypertension. N Engl J Med. 2003 Jun 12;348(24):2407-15. [abstract]
- McGrath BP; Ambulatory blood pressure monitoring. Med J Aust. 2002 Jun 17;176(12):588-92. [abstract]
- Mancia G, Parati G; Office compared with ambulatory blood pressure in assessing response to antihypertensive treatment: a meta-analysis. J Hypertens. 2004 Mar;22(3):435-45. [abstract]
- Ernst ME, Bergus GR; Ambulatory blood pressure monitoring. South Med J. 2003 Jun;96(6):563-8. [abstract]
- Haydar AA, Covic A, Jayawardene S, et al; Insights from ambulatory blood pressure monitoring: diagnosis of hypertension and diurnal blood pressure in renal transplant recipients. Transplantation. 2004 Mar 27;77(6):849-53. [abstract]
- Fagard RH, Staessen JA, Thijs L, et al; Relationship between ambulatory blood pressure and follow-up clinic blood pressure in elderly patients with systolic hypertension. J Hypertens. 2004 Jan;22(1):81-7. [abstract]
- O'Brien E, Beevers G, Lip GY; ABC of hypertension: Blood pressure measurement. Part IV-automated sphygmomanometry: self blood pressure measurement. BMJ. 2001 May 12;322(7295):1167-70.
Acknowledgements
EMIS is grateful to Dr Gurvinder Rull for writing this article. The final copy has passed scrutiny by the independent Mentor GP reviewing team. ©EMIS 2010.Document ID: 1792
Document Version: 21
Document Reference: bgp24487
Last Updated: 3 Aug 2010