What is ambulatory blood pressure monitoring? Cardiology Basics

What is ambulatory blood pressure monitoring? Cardiology Basics

Usually blood pressure is measured with two or three recordings in the clinic or at the bedside. Blood pressure is known to fluctuate throughout the day depending on activities and stress. So, a recording from the clinic may not reflect the average blood pressure during a 24 hour period. Studies have shown that average daily blood pressure is more important than single recordings in deciding the target organ damage due to hypertension.

In ambulatory blood pressure monitoring, a blood pressure cuff applied to the arm is automatically inflated and deflated periodically by a battery driven device attached to the belt. Recordings may be programmed at 15-30 minute intervals. Intervals at night may be programmed higher to facilitate sleep.

After a 24 hour period, the device is removed and connected to the computer with ambulatory blood pressure monitoring software. The system gives a computer analysis and print out of the average daily blood pressure, average day time blood pressure and average nighttime blood pressure. Heart rate and blood pressure trends may also be printed.

As per the guidelines of the American Heart Association, confirming of a diagnosis of hypertension by ambulatory monitoring is strongly recommended. In most persons the systolic blood pressure decreases 10% to 20% during sleep. They are called “dippers”. There are also “non-dippers” in whom blood pressure does not decrease during sleep and few in whom blood pressure may even rise during sleep.

There are certain persons whose blood pressure increases with the anticipation of measurement in the health care setting but are normal in other situations. This is known as “White coat hypertension or white coat syndrome”. Usually they will not have target organ damage due to hypertension and needs no treatment. But now there is a view that they need surveillance as they might develop sustained hypertension later.

Then there is a group who have elevated blood pressure when recorded from home but have normal blood pressure recorded in the health care setting. This is known as “Masked hypertension” and has the same risk as sustained hypertension. Finally, there is the more common situation of those who have elevated blood pressure recording while at home as well as at the clinic. That is known as sustained hypertension. Sustained hypertension is associated with target organ damage.

Ambulatory recordings are useful in identifying these different subgroups of hypertension. Response to medications can also be assessed with ambulatory blood pressure recordings. Ambulatory monitoring will document whether the medication is controlling hypertension throughout the day or only at certain times of the day.

Hypertension in pregnancy and in those with borderline hypertension can also be assessed by ambulatory recordings. When some other medications produce changes in the blood pressure pattern, that also can be identified by ambulatory recording. It may also be useful in the evaluation of those who get syncopal episodes with hypotension. In that case, ambulatory recordings help to correlate symptoms with corresponding blood pressure level.

Repeated blood pressure recordings during ambulatory monitoring may produce some discomfort to the person due to repeated cuff inflation. Some tenderness or rashes may also occur at the site of cuff application. But these are self-limited problems which will disappear in a day or two. Cuff inflations at night might interfere with sleep and that is why the measurement interval is usually programmed longer at night.