What is 24-hour ambulatory blood pressure monitoring?
Twenty-four-hour ambulatory blood pressure monitoring is a way of measuring and managing high blood pressure (hypertension). Hypertension is a blood pressure measurement in which the systolic (upper) blood pressure is at or above 140 and the diastolic (lower) blood pressure is at or above 90.
Ambulatory blood pressure monitoring allows many blood pressure (BP) readings to be recorded over a 24-hour period, whether the patient is awake or asleep. At a doctor’s office or clinic, an instrument called a sphygmomanometer is used to take BP readings. Usually, only one or two readings are taken during a doctor’s visit. However, ambulatory BP monitoring yields many readings over a continuous period.
In most cases, with ambulatory BP monitors, readings are taken every 20 to 30 minutes during the day and every hour at night. The heart rate can also be measured at the same time.
Multiple BP readings can be averaged over the 24-hour period to obtain the mean or average BP. Variations in BP and heart rate, the BP distribution pattern, and other statistics can be calculated.
Why is 24-hour ambulatory blood pressure monitoring used?
Ambulatory BP monitoring provides additional information about how your changes in BP may correlate with your daily activities and sleep patterns. The United States Preventive Services Task Force (USPSTF) now recommends confirming a diagnosis of hypertension with ambulatory BP monitoring.
For most people systolic BP decreases about 10%-20% during sleep. However, for some people BP might not drop during sleep and may even rise.
Ambulatory BP monitoring can detect abnormal fluctuations in BP that might go unnoticed when BP is only measured in the doctor’s office. It is a very useful way to detect white coat hypertension, masked hypertension, and sustained hypertension:
- White coat hypertension: Some people who do not take BP lowering drugs (antihypertensive drugs) have elevated BP readings when their BP is taken at a doctor’s office or other health care setting. This is known as “white coat hypertension.” White coat hypertension can result in misdiagnosis of patients whose BP is actually normal. White coat hypertension has been observed in 15%-30% of patients with elevated BP readings. When ambulatory monitoring yields readings within the normal range outside the doctor’s office, patients usually do not need to take antihypertensive drugs.
- Masked hypertension: This condition occurs when a patient’s BP reading is normal at the doctor’s office, but is elevated when the patient is at home. It may occur in up to 20% of people who are being treated for hypertension.
- Sustained hypertension: This refers to BP readings that are elevated whether the patient is in the doctor’s office or at home. This condition has been linked to an increased likelihood of heart and kidney damage.
Are there other uses for 24-hour ambulatory blood pressure monitoring?
Ambulatory BP monitoring is increasingly being used to determine how well some antihypertensive drugs can control high BP. In some cases, antihypertensive drugs do not control BP effectively throughout the entire day and night. A doctor may need to adjust the dosage prescribed or the time that the medication is given, depending on the patient’s BP patterns. In other cases, more than one drug may be required to stabilize BP.
Ambulatory BP monitoring can also help to predict the likelihood of cardiovascular (blood vessels in the heart) and cerebrovascular (blood vessels in the brain) disease linked to hypertension and organ damage.
Ambulatory BP monitoring may also be suitable in other situations, such as for:
- Pregnant women with hypertension
- Patients with “borderline” hypertension
- Difficulty controlling BP with medication
- BP changes due to other drugs
- Changes in prescription medications that may impact BP
- Fainting episodes or hypotension (low BP)
What are benefits associated with 24-hour ambulatory blood pressure monitoring?
Ambulatory monitoring can rule out white coat hypertension, so that patients are not given unnecessary prescriptions for BP-lowering drugs. It can also detect masked hypertension, so that patients receive the medications needed for high blood pressure. The incidence of stroke, heart disease, and organ damage due to hypertension can be reduced among those patients. Ambulatory monitoring may also be useful in evaluating a patient’s response to long-acting antihypertensive medications.
What are disadvantages of 24-hour blood pressure monitoring?
You may experience some discomfort due to 24-hour BP monitoring. Pressure due to repeated inflation of the cuff can cause soreness in the upper arm. BP readings during the night may interfere with your sleep. The cuff may also irritate the skin and cause a mild rash on the arm that usually goes away on its own. Some insurance carriers do not reimburse patients for using the ambulatory devices, unless white coat hypertension is suspected.