Ambulatory Blood Pressure Monitoring

Ambulatory Blood Pressure Monitoring (ABPM) is a non-invasive 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.¹

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 over night e.g. 1 hourly).

• Get 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.^2,3
• Detect white coat hypertension.
• Use in hypertension research e.g. reviewing 24 hour profile of anti-hypertensive medication.
• May have prognostic use - higher readings on ABPM are associated with increased mortality (see below).⁴
• May be more cost effective in the long-term.

• 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. suspect 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. diabetes mellitus, cerebrovascular disease and renal transplant recipients.^5,6
• Suspicious of white coat hypertension - high blood pressure readings in clinic which are normal at home.
• Suspicious of reversed white coat hypertension - i.e. blood pressure readings are normal in clinic but raised in patients own environment.
• Postural hypotension.
• Elderly patients with systolic hypertension.⁷

• Not widely available.
• 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.⁸

• This varies according to the machines used.
• Night time mean, day mean and overall mean are also provided.
• Usually 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 are more associated with risk of developing target end-organ damage.

• 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 worse outcome.^2,5
• 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 poorer outcome.