Ambulatory Blood Pressure Monitoring

CHAPTER 84 Ambulatory Blood Pressure Monitoring



Russell D. White, Thomas H. Mitchell


Ambulatory blood pressure monitoring (ABPM) is an automated, noninvasive technique for obtaining blood pressure measurements at predetermined intervals over an extended period of time (usually 24 hours or more) while the patient goes about his or her daily activities. The process involves attaching a measuring and recording device to the patient. These devices are lightweight and use either the auscultatory (i.e., microphone and Korotkoff’s sounds) or the oscillometric method (i.e., senses arterial waves) to determine blood pressure. Although the auscultatory method needs low ambient noise levels to obtain its most accurate results, it tolerates patient movement better than the oscillometric method. In contrast, although the oscillometric method tolerates high levels of environmental noise, it is most accurate when the patient is less physically active. The recordings can be downloaded for analysis.


Hypertension has traditionally been defined as an office systolic blood pressure of 140 mm Hg or higher and diastolic blood pressure of 90 mm Hg or higher; however, it is now defined at lower levels for patients with diabetes or target organ damage (e.g., left ventricular hypertrophy, heart failure, angina or prior myocardial infarction, prior coronary revascularization, stroke or transient ischemic attack, dementia, chronic kidney disease [glomerular filtration rate <60 mL/min], peripheral arterial disease, retinopathy), and elevated systolic blood pressure is frequently isolated (i.e., elevated in the absence of elevated diastolic blood pressure). Over 50 million Americans are hypertensive, a major risk factor for such common diseases as cardiovascular disease, stroke, aortic aneurysm rupture, renal failure, and retinopathy. Because some patients are hypertensive only during specific hours of the day, documentation of adequate blood pressure control over 24 hours is imperative to prevent sequelae. Studies have shown that hypertension diagnosed with ABPM more often correlates with target organ damage than hypertension noted on sporadic blood pressure measurements in the office setting (especially in patients with albuminuria or echocardiographically determined left ventricular hypertrophy). Patients whose average pressures by 24-hour ABPM are greater than 135/85 mm Hg have twice the risk for a cardiovascular event compared with those with 24-hour mean blood pressures less than 135/85 mm Hg, regardless of the blood pressures measured in the office. In most people, blood pressure decreases by 10% to 20% at night; those without such a reduction (i.e., nondippers) are at increased risk of cardiovascular events. Conversely, overtreatment of hypertension can lead to complications such as transient hypotension, dizziness, and myocardial ischemia. In addition, as many as 21% of patients with mild blood pressure elevation in the office are incorrectly diagnosed with and treated for hypertension. Likewise, although having the patient monitor his or her blood pressure at home (i.e., self-monitored blood pressure) can improve blood pressure control, it has been difficult to correlate such a practice with fewer cardiovascular events. Therefore, ABPM offers an alternative to both office and home blood pressure measurements, facilitating both the diagnosis and the management of hypertension.



Indications


Routine sporadic blood pressure measurements in the office setting remain the recommended method to screen for and monitor hypertension. ABPM should not be used indiscriminately as a screening device. However, because blood pressure measurements in the office can lead to both false-positive and false-negative results, ABPM can be useful for finalizing the diagnosis. Figure 84-1 provides a helpful algorithm. Indications may include the following:


• Normal or borderline office hypertension with target organ damage (defined by the American Heart Association [AHA] and the National Institutes of Health [NIH] Joint National Committee’s [JNC] Seventh Report as left ventricular hypertrophy, heart failure, angina or prior myocardial infarction, prior coronary revascularization, stroke or transient ischemic attack, dementia, chronic kidney disease [glomerular filtration rate <60 mL/min], peripheral arterial disease, retinopathy)

• Persistent office hypertension without target organ damage

• Discrepancy between office and home blood pressure measurements (especially in diabetic and elderly patients)

• Considerable blood pressure variability found during same office visit or over different visits

• Episodic hypertension (e.g., smoking raises blood pressure acutely, and the level returns to baseline about 15 minutes after stopping)

• Episodic angina or pulmonary congestion unrelated to exercise

• Determination of the duration or efficacy of antihypertensive medications during the 24-hour treatment cycle

• Dosage adjustment of antihypertensive medications

• Documented hypertension unresponsive to treatment (“drug resistance”)

• Suspected pressor (“white coat”) hypertension and no target organ damage

• Office blood pressure elevated during pregnancy and preeclampsia suspected

• Autonomic dysfunction

• Hypotensive symptoms while on antihypertensive medication

• Evaluation of syncope or pacemaker syndromes

image

Figure 84-1 Algorithm for appropriate use of ambulatory blood pressure monitoring (ABPM). CCD, clinical cardiovascular disease; SBP, systolic blood pressure; TOD, target organ damage. *Major cardiovascular risk factors in patients with hypertension (Joint National Congress VI) include smoking, dyslipidemia, diabetes, age older than 60, gender (men and postmenopausal women), and family history of early cardiovascular disease. †The proportion of blood pressures during the monitoring period that are increased relative to preset thresholds (140/90 mm Hg awake, 120/80 mm Hg asleep).


(Updated from Ernst ME, Bergus GR: Ambulatory blood pressure monitoring: Technology with a purpose [editorial]. Am Fam Physician 67:2262–2263, 2003; with permission.)



Contraindications and Limitations



• Cost: some insurance companies may not reimburse for ABPM

• Irregular, rapid heart rate: limits ability to obtain blood pressure measurements and limits the accuracy of ABPM

• Severe obesity: limits ability to obtain blood pressure measurements and limits the accuracy of ABPM

• Severe patient anxiety regarding instrument


Preprocedure Patient Preparation


The procedure should be explained to the patient as well as its risks, benefits, and any alternatives. Obtain either verbal or written consent. Patients should be instructed to record any symptoms or events that occur during the monitoring period and any medications they are taking (and when they take them). In most cases, they should be instructed not to speak or move during cuff deflation (recording phase). Patients should also usually avoid strenuous activity (e.g., running or racquet sports) during the study. They should know how long they will be monitored, where to go to have the equipment removed, and when they might expect the results. If not contraindicated, the clinician may choose to offer the patient a sleep medication to minimize the equipment’s interference with sleep.



Equipment



• Monitor (with instructions) for ABPM

• Automatic blood pressure cuff and sphygmomanometer

• Connectors and tubing

• 24-hour diary for events, activities, and medications


Technique



1 The clinician should follow the manufacturer’s instructions for attaching the equipment and performing the procedure. However, this usually means placing the microphone/sensor over the brachial artery proximal to the elbow of the nondominant arm (Fig. 84-2). Proper positioning of the microphone/sensor is critical.

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May 14, 2017 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Ambulatory Blood Pressure Monitoring

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