24-HOUR AMBULATORY BLOOD PRESSURE MONITORING

Ambulatory blood pressure monitoring (ABPM) is a non-invasive method of measuring your blood pressure and obtaining your blood pressure readings at regular intervals (usually every 15 – 30 minutes) over a 24-hour period whilst you go about your normal daily activities including sleep in your own environment (at work or at home).  It therefore represents a true reflection of your blood pressure outside a clinic office.

Your blood pressure fluctuations over this period form the ABPM pattern.  This pattern will allow your doctor to decide whether you have high blood pressure and whether treatment of the blood pressure is required (if in doubt).

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 (e.g. stroke and heart attack) and target organ damage (e.g. heart, brain and kidneys)

 

What does ambulatory blood pressure monitoring involve?

Blood pressure is measured over a 24-hour period using a digital device that is designed to measure your blood pressure by inflating a cuff around your upper arm then slowly releasing the pressure.  The device 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 (see figure 1).

At PYCC this test is made simpler by using a wrist watch (BPro HealthStat).  The BPro device wears like a watch with no cuff and does not inflate.  It is therefore more convenient and comfortable with no disruption to normal daily activities or sleep (see figure 2).

Because the test is designed to evaluate what your normal daily blood pressure is, it is important to carry on with your daily routine activities and do all the things you would normally do.  The only things you should avoid for the day is to participate in sports activities that involve the use of your arms/hands.  You can even shower wearing the BPro watch.

 

What you need to do during the 24-hour blood pressure monitoring period?

To allow the device to work properly, it is important to make sure the interrogative device is properly positioned on the wrist pulse (radial artery).  The technician will ensure this and secure the device with tapes to prevent shifting of the correct position.  When it is recording, ensure the arm is kept still and the wrist is not in active motion.

 

Why do you need a 24-hour Blood pressure monitoring?

By measuring your blood pressure at regular intervals over 24 hours, your cardiologist is able to get clear information of how your blood pressure changes throughout the day. There are a number of reasons why your cardiologist might suggest this test:

  • He 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”).
  • He may want to see how well your medicines are working, to make sure they are controlling your blood pressure throughout the day.
  • He may want to see if your blood pressure stays high at night. If this is the case, he may need to change or adjust your medicines.

 

What are the uses of ambulatory blood pressure monitoring?

  • To obtain a 24-hour record which is more reliable than one-off measurements in the clinic. 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 (i.e. thickening of the muscles of the heart chambers) and prognostic use in predicting stroke, heart attack, sudden death.
  • To detect white-coat hypertension (i.e. your blood pressure may be high in the clinic being checked by the doctor but normal outside the clinic in your own environment).
  • Suspected masked hypertension (untreated individual with normal clinic blood pressure but elevated ABP outside clinic).
  • Suspected nocturnal (night) hypertension or no night-time blood pressure reduction which is usually the normal physiological response.
  • Uncontrolled high blood pressure despite appropriate treatment
  • Individuals with a high risk of future cardiovascular events (even if clinic blood pressure is normal).
  • Suspected episode hypertension
  • Reviewing 24-hour profile of antihypertensive medicines
  • Hypotensive (too low blood pressure) whilst on antihypertensive medicines.

Ambulatory blood pressure monitoring is also useful for :

  • Titrating antihypertensive medications
  • Borderline hypertension
  • Hypertension detected early in pregnancy
  • Suspected or confirmed sleep apnea

Syncope (fainting episodes) or other symptoms suggesting postural (orthostatic) hypotension (positional low blood pressure), where this cannot be demonstrated in the clinic.

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Figure 1.  Usual ambulatory blood pressure monitoring device (courtesy of HealthStats)

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Figure 2. The wrist BPro device