Twenty-four-hour ambulatory blood pressure monitoring
=====================================================

* Ann Bugeja
* Ayub Akbari
* Swapnil Hiremath

## Twenty-four-hour ambulatory blood pressure monitoring (ABPM) is recommended for the diagnosis of hypertension

Indications for ABPM include concern for white-coat hypertension (i.e., when blood pressure is higher in v. out of the clinic) or masked hypertension (i.e., when blood pressure is higher out v. in the clinic), and evaluation of blood pressure that remains above target thresholds despite appropriate therapy.1,2 An average awake blood pressure of 135/85 mm Hg or higher, or an average 24-hour blood pressure of 130/80 mm Hg or higher is considered high (Appendix 1, available at [www.cmaj.ca/lookup/doi/10.1503/cmaj.220990/tab-related-content](http://www.cmaj.ca/lookup/doi/10.1503/cmaj.220990/tab-related-content)).1

## Ambulatory blood pressure monitoring can uncover nocturnal hypertension

A minimum of 20 readings while the patient is awake and 7 while the patient is asleep are required for complete evaluation. Normally, blood pressure decreases by 10% during sleep. An average nocturnal blood pressure of 120/70 or higher is considered nocturnal hypertension, which can be seen with volume overload and sleep apnea, and is associated with adverse cardiovascular outcomes.3

## Masked hypertension can be diagnosed with ABPM

Masked hypertension is common, with prevalence ranging from 10% in the general population to as high as 30%–40% among people with comorbid conditions such as diabetes or kidney disease.3,4 It is associated with the same cardiovascular risk as untreated hypertension.1

## Ambulatory blood pressure monitoring is underused despite being cost-effective

Only 14% of family physicians in Canada report using ABPM.1,4 Ambulatory blood pressure monitoring has an incremental cost-effectiveness ratio of $30 per quality-adjusted life-year (far below the common threshold of $50 000), but variable coverage across all provinces may contribute to its underuse.2

## Home measurement of blood pressure is an alternative when ABPM is not affordable

Accurate daytime home monitoring is acceptable for those without timely access to ABPM, as home measurement is a less expensive out-of-office option, and allows identification of white-coat and masked hypertension.1 However, it cannot provide a detailed assessment of variability in blood pressure, and cannot identify nocturnal hypertension.5

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## Footnotes

*   **Competing interests:** Ayub Akbari reports grants from Otsuka, as well as grants, consulting fees and honoraria from AstraZeneca. Swapnil Hiremath serves as a vice-president of NephJC, a nonprofit registered in the United States, which is an unpaid position. No other competing interests were declared.

*   This article has been peer reviewed.

This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY-NC-ND 4.0) licence, which permits use, distribution and reproduction in any medium, provided that the original publication is properly cited, the use is noncommercial (i.e., research or educational use), and no modifications or adaptations are made. See: [https://creativecommons.org/licenses/by-nc-nd/4.0/](https://creativecommons.org/licenses/by-nc-nd/4.0/)

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