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Ambulatory blood pressure monitoring: methodologic issues
L M Prisant1, P B Bottini, A A Carr
1Section of Hypertension, Medical College of Georgia, Augusta, USA.
Insights
Ambulatory blood pressure monitoring offers a dynamic assessment of blood pressure, correlating better with organ damage than office readings. However, significant variability exists even with repeat measurements, impacting its routine clinical use.
Area of Science:
- Cardiology
- Physiology
- Medical Devices
Background:
- Blood pressure is a dynamic physiologic variable, unlike static office measurements.
- Ambulatory blood pressure monitoring (ABPM) provides intermittent recordings throughout the day.
- Office blood pressure readings are susceptible to placebo and physician pressor effects, leading to patient variability.
Purpose of the Study:
- To highlight the advantages of ABPM over traditional office blood pressure measurements.
- To discuss the methods and interpretation of ABPM.
- To address the variability and limitations of ABPM in clinical practice.
Main Methods:
- Utilizing portable devices for intermittent blood pressure recording.
- Employing auscultatory and oscillometric methods for blood pressure detection.
- Assessing 24-hour blood pressure and diurnal changes.
Main Results:
- ABPM correlates more strongly with target organ damage than office measurements.
- A 24-hour ambulatory blood pressure mean of 140/90 mm Hg or above is abnormal.
- Repeat ABPM measurements show high variability (approx. 50%) in mean differences within a week.
Conclusions:
- ABPM offers a more accurate reflection of a patient's blood pressure profile.
- Despite advantages, significant test-retest variability in ABPM necessitates cautious interpretation.
- Further European trials are investigating the prognostic value of ABPM in hypertension management.
Abstract:
Blood pressure, like heart rate, is a changing physiologic variable. Like ambulatory electrocardiography, ambulatory blood pressure can be recorded intermittently throughout the day. Ambulatory blood pressure is a dynamic variable influenced by multiple factors, and it correlates more strongly with target organ damage than do static office blood pressure measurements. Office (but not ambulatory) measurements are subject to the placebo and physician pressor effect. There is a great patient variability of blood pressure measurements in the office compared with ambulatory methods. Ambulatory blood pressure devices are portable rather than 'ambulatory'. The auscultatory (listens for Korotkoff sounds) and oscillometric (detects maximal arterial vibrations and calculates diastolic blood pressure) methods are used to detect blood pressure. Equipment is generally safe, although mild sleep derangements have been reported. The 24-h blood pressure and diurnal change are usually assessed. A 24-h ambulatory blood pressure mean of 140/90 mm Hg or above is clearly abnormal, though recent data suggest that the 95th centile is 134/84 mm Hg. Correlation of individual blood pressure readings with diary entries may be instructive. New American and British validation criteria have been published to assess the performance of each new device that becomes available. It should not be assumed that newer ambulatory devices have been tested (particularly by a third party) or are better. Test/retest 24-h ambulatory blood pressure shows less variability than office measurements; however, the percentage of patients with a mean difference greater than +/- 5 mm Hg on repeat 24-h blood pressure measurement after 1 week is still surprisingly high (49.3%, systolic; 52.1%, diastolic). European trials are in progress to assess the prognosis of hypertension assessed by ambulatory compared with office blood pressure. Ambulatory blood pressure monitoring has been restricted for use in several clinical situations and is not used for the routine evaluation and management of hypertension.