Ambulatory Blood Pressure Monitoring

Michael E. Ernst, PharMD, BCPS, George R. Bergus, MD

Disclosures

South Med J. 2003;96(6) 

In This Article

Clinical Applications of Ambulatory Blood Pressure Monitors

Published recommendations exist for the clinical use of ABPM.[1,2,3,4,5,6] The most recent Joint National Committee report outlines clinical situations where ABPM may be helpful, including suspected white-coat hypertension, drug resistance, hypotensive symptoms, episodic hypertension, and autonomic dysfunction.[3] These and other indications are shown in Table 2 .

The utility of ABPM in clinical practices has been assessed. In a case series of 318 patients, the principal reasons for referral to ABPM were blood pressure lability, disparity between home and office readings, poor blood pressure control, suspected secondary cause of hypertension, and suspected white-coat hypertension.[9] Almost half of the patients receiving medication had changes in antihypertensive therapy in response to the data obtained from ABPM, and 9% were able to discontinue at least one medication. In the second report, 60 patients were referred by their physician to a clinical pharmacist 24-hour ABPM service.[10] Primary reasons for referral included evaluation of suspected isolated office hypertension, drug resistance, blood pressure control in diabetic patients, and suspected drug-induced orthostatic hypotension. Unnecessary antihypertensive therapy was avoided in 12 of 40 patients confirmed from ABPM to have white-coat hypertension.

Suspected white-coat hypertension is a widely recognized indication for ABPM. Because decisions regarding antihypertensive therapy are often made on the basis of isolated office blood pressure readings, patients with white-coat hypertension may be incorrectly diagnosed with sustained hypertension. This phenomenon has been reported in 15 to 35% of patients currently labeled and treated as hypertensive.[11] Although controversy exists regarding whether white-coat hypertension should be treated, several studies have suggested it signals a "prehypertensive" state that eventually evolves into sustained hypertension. Thus, white-coat hypertension may precede sustained hypertension, much as impaired glucose tolerance can precede diabetes. Noninvasive ABPM is helpful for identifying patients with elevated office pressure and normal pressure outside the health care setting.

Resistant hypertension is defined as the inability to reach target blood pressure lower than 140/90 mm Hg despite triple-drug regimens in appropriate dosages.[3] Ambulatory monitoring of blood pressure helps evaluate whether additional therapy is needed. It also helps determine whether a "white-coat" element is superimposed on existing hypertension. Brown et al. used ABPM to evaluate 611 patients with elevated office pressure, divided into three groups: those not taking antihypertensives (n = 277), those taking one to two antihypertensives (n = 216), and those taking three or more antihypertensives (n = 118).[12] Twenty-eight percent of the resistant hypertensives had normal awake ambulatory blood pressure (ABP). They concluded that approximately one in four patients with apparent resistant hypertension actually have controlled blood pressure, and ABPM is an appropriate initial step before ordering further workup in these patients.

Patients with borderline elevations in blood pressure can benefit from ABPM. No consensus definition of borderline hypertension exists, but it generally refers to patients with some (but not all) elevated office and/or home blood pressure. Patients with "high-normal" blood pressure according to the Sixth Report of the Joint National Committee may also be included. Because of the disparate readings often obtained during infrequent office visits, clinicians are challenged with the decision of whether medications are necessary. A high proportion of patients with borderline hypertension may actually exhibit white-coat hypertension.[13] Measurements obtained be means of ABPM can provide additional information for risk stratification in patients with borderline elevations in blood pressure.

Ambulatory monitoring of blood pressure is useful for assessing adequacy of antihypertensive therapy. Investigators in the Ambulatory Blood Pressure Monitoring and Treatment of Hypertension trial[14] investigated whether the use of ABPM compared with conventional measurement leads to less intensive treatment with drugs and fewer side effects while maintaining blood pressure control. In this trial, 419 patients were assessed by either office blood pressure or ABPM measurements performed at baseline and at 1, 2, 4, and 6 months. Antihypertensive therapy was adjusted in a stepwise fashion on the basis of these measurements. By the end of the 6-month study, significantly more patients in the ABPM group had discontinued all antihypertensive therapy (26.3 versus 7.3%; P < 0.001) and fewer progressed to multiple-drug treatment compared with the conventional measurement group (27.2 versus 42.7%; P < 0.001).

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