Ambulatory BP monitoring to guide pharmacotherapy for hypertension

Issue: October 2012

ByMichael Brenner, PharmD, BCPS

Office or clinic BP is the most commonly used BP measurement to assist with the management of hypertension. However, clinic BP measurement may overestimate a patient’s actual BP value. Use of ambulatory BP monitoring (ABPM) has grown in recent years to address this issue. Initially used for research purposes, ABPM is increasingly used in cardiology specialty clinics to guide hypertension therapy.

The Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC 7) guidelines identified clinical indications for which ABPM is helpful, including suspected white-coat hypertension, drug resistance and treatment-related hypotensive symptoms, but the guideline did not recommend routine use. The newest UK National Institute for Health and Clinical Excellence (NICE) guidelines now recommend that ABPM be used to confirm the diagnosis of hypertension.

Guideline updates

Michael Brenner

The update to the NICE hypertension guideline, published in 2011, emphasizes using ABPM to confirm hypertension diagnosis. It recommends that ABPM be offered to confirm diagnosis for patients with office BP =140 mm Hg/90 mm Hg. A minimum of two measurements taken per hour while the patient is awake and an average of no less than 14 measurements are recommended for diagnosis confirmation via ABPM. For stage 1 hypertension (office BP =140 mm Hg/90 mm Hg), ABPM would average =135 mm Hg/85 mm Hg; for stage 2 hypertension (office BP =160 mm Hg/100 mm Hg), ABPM would average =150 mm Hg/95 mm Hg for the diagnosis of hypertension to be confirmed.

Argument to use ABPM

The NICE guideline argues that ABPM is more accurate than clinic and home monitoring in defining the presence of hypertension, and that implementation of a diagnostic strategy for hypertension using ABPM, following an initial raised clinic BP reading, would reduce misdiagnosis and be cost-saving for the UK National Health Service (NHS).

ABPM has many advantages that also make it useful for assistance in hypertension management. ABPM can assess BP variability throughout the day, as well as assess mean values during a 24-hour period. This enables BP load on the heart and peripheral circulation to be measured. Evidence also supports that mean 24-hour BP values more closely correlate with surrogate measures of target-organ damage (ie, left ventricular hypertrophy, proteinuria) and CV endpoints than clinic BP measurements. ABPM can be used to document presence of white-coat or masked hypertension, resistant and labile hypertension or postural hypotension, all of which can be relatively difficult to correctly identify using office BP alone. ABPM can also document morning surges in BP likely associated with neurohormonal variability early in the wake cycle. In addition, ABPM can identify whether a patient is a dipper (BP decreased =10% during sleep) or nondipper. This distinction is important, as nondipping status has been linked to increased risk for CV events and end-organ damage. ABPM can also detect the individualized percentage of elevated BP readings per day.

Guidance for pharmacotherapeutic decisions

Use of ABPM has the potential to simplify a pharmacotherapy regimen, which may provide medication cost-savings and improve patient adherence. However, there are a lack of clinical trial data and no mention of this potential in the updated NICE hypertension guidelines. Studies that have examined the role of ABPM for guiding therapy in hypertension management are small and limited, but warrant discussion.

Staessen and colleagues conducted a multicenter, randomized, parallel-group study on 419 patients to compare ABPM with conventional BP monitoring for management of elevated diastolic BP (DBP) =95 mm Hg. The objective was to test the hypothesis that ABPM would lead to less-intensive treatment while preserving BP control. Antihypertensive therapies were intensified, reduced or unchanged based on daytime DBP. Follow-up visits were scheduled at 1, 2, 4 and 6 months. In the ABPM group, 26.3% patients had their hypertensive agents discontinued vs. 7.3% patients in the conventional BP monitoring arm (P<.001). Fewer patients in ABPM group progressed to sustained multiple drug therapy (27.2% vs. 42.7%; P<.001). This study demonstrated that ABPM might lead to less antihypertensive therapy while preserving BP control.

Conen and colleagues conducted a multicenter, randomized, controlled, open-label, parallel-group trial of 165 patients. Results confirmed previous findings and expanded on the use of ABPM to guide antihypertensive management. Patients with two office BP measurements >140 mm Hg/90 mm Hg and average 24-hour BP >130 mm Hg/80 mm Hg were randomly assigned to ABPM or standard office BP monitoring. BP was measured via ABPM and in the office at baseline, 1 month, 6 months and 1 year. After 1 year, the reduction of systolic BP (SBP) was 13.5 mm Hg in ABPM group vs. 9.8 mm Hg in the standard office BP group (P=.03). Patients in the ABPM group were on fewer antihypertensive agents to achieve BP control (1.76 ± 1.1 vs. 1.95 ± 0.9; P=.049). However, subgroup analysis revealed the benefits of ABPM occurred only in patients taking antihypertensive therapy before study enrollment compared with antihypertensive-naive patients (mean difference, –7.2; P=.002). There was no difference in BP reduction in newly diagnosed patients (mean difference, –0.2; P=.93).

ABPM can also be used clinically to assess antihypertensive regimen efficacy. The 24-hour BP distribution can allow evaluation of whether the accuracy of dosing intervals is accurate and to ensure 24-hour BP reduction. Elimination half-lives of once-daily medications can vary among patients and among antihypertensive classes and agents within a class. ABPM provides a unique tool to examine the BP reduction after a medication is taken and throughout the entire dosing interval. In the case of short-acting agents, ABPM can detect whether the BP-lowering effect is wearing off or lost by the end of the dosing interval. Using this information can be helpful in determining which antihypertensive agent or class would benefit a particular patient, especially in the case of a patient with treatment-resistant BP.

Additionally, ABPM might be useful in guiding the timing of administration of antihypertensive agents. A patient classified as a nondipper has the common hypertensive pattern of elevated morning BP readings relative to BP readings throughout the rest of the day. These patients may benefit from having antihypertensive(s) dosed at bedtime to avoid significant reductions in daytime BP while controlling/preventing the morning surge in BP. Conversely, a dipper may best be treated with an antihypertensive dosed in the morning. ABPM could allow individualization of treatment regimen based on these patient-specific factors and improve safety, compliance and, potentially, outcomes. If a patient develops daytime dizziness, ABPM could be used to assess daytime BP to determine whether an antihypertensive regimen should be altered. Changing the administration time or dosing interval may help reduce the frequency of hypotension and falls.

Lastly, although current US guidelines suggest that the initial selection of antihypertensive agent(s) should be based on a patient’s compelling indication and add-on therapy should be based on BP response and medication tolerance, ABPM can provide useful assistance starting a new dose or when BP response is not as expected. If ABPM detects normal BP levels in a patient with questionable or mild hypertension, then a low-dose antihypertensive could be used for a particular compelling indication while minimizing the risk for hypotension.

Medicare currently limits coverage of ABPM to patients with suspected white-coat hypertension. Private insurers typically cover a wider variety of indications for ABPM (resistant or masked hypertension, episodic hypotension, evaluate current therapy, etc). Reimbursement rates vary based on region, patient health and insurance policies. ABPM use is likely to expand as a result of its inclusion in the latest NICE hypertension guidelines and as emerging evidence from clinical trials broadens the scope and indications for use.

Michael Brenner, PharmD, BCPS (AQ Cardiology), is clinical pharmacy specialist, cardiology, at VA Ann Arbor Healthcare System in Ann Arbor, Mich.

Rhonda M. Cooper-DeHoff, PharmD, MS, is associate professor in the department of pharmacotherapy and translational research, College of Pharmacy, and division of cardiovascular medicine, College of Medicine, University of Florida, Gainesville. Cooper-DeHoff is Cardiology Today’s Pharmacology Consult column editor and a member of the CHD and Prevention section of the Editorial Board.

For more information:

Conen D. J Hum Hypertens. 2009;23:122-129.
National Institute for Health and Clinical Excellence. Chronic obstructive pulmonary disease. Available at: www.nice.org.uk/guidance/CG12.
Pickering TG. N Engl J Med. 2006;354:2368-2374.
Staessen JA. JAMA. 1997;278:1065-1072.

Disclosures:

Brenner reports no relevant financial disclosures.

Rhonda M. Cooper-DeHoff, PharmD, MS, FAHA, FACC, can be reached at the College of Pharmacy at University of Florida, Gainesville, PO Box 100486, Gainesville, FL 32610; her email is: dehoff@cop.ufl.edu.