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Hypertension - Diagnosis BLOOD PRESSURE MEASUREMENT AND CLINICAL EVALUATION Hypertension is defined as systolic blood pressure (SBP) of 140 mm Hg or greater, diastolic blood pressure (DBP) of 90 mm Hg or greater, or taking antihypertensive medication. The objective of identifying and treating high blood pressure is to reduce the risk of cardiovascular disease and associated morbidity and mortality. To that end, it is useful to provide a classification of adult blood pressure for the purpose of identifying high-risk individuals and to provide guidelines for followup and treatment.
The positive relationship between SBP and DBP
and cardiovascular risk has long been recognized.
This relationship is strong, continuous, graded,
consistent, independent, predictive, and etiologically
significant for those with and without coronary
heart disease. Therefore, although classification
of adult blood pressure is somewhat
arbitrary, it is useful to clinicians who must make
treatment decisions based on a constellation of
factors including the actual level of blood pressure.
Table 2 provides a classification of blood
pressure for adults (age 18 and older). These criteria
are for individuals who are not taking anti-hypertensive
medication and who have no acute
illness. This classification is based on the average
of two or more blood pressure readings taken in
accordance with the following recommendations
at each of two or more visits after an initial
screening visit. When SBP and DBP fall into
different categories, the higher category should
be selected to classify the individual’s blood pressure.
The classification is slightly modified from
the JNC V report in that stage 3 and stage 4
hypertension are now combined because of the
relative infrequency of stage 4 hypertension.
DETECTION AND CONFIRMATION Hypertension detection begins with proper blood pressure measurements, which should be obtained at each health care encounter. Repeated blood pressure measurements will determine whether initial elevations persist and require prompt attention or have returned to normal and need only periodic surveillance. Blood pressure should be measured in a standardized fashion using equipment that meets certification criteria. The following techniques are recommended:
SELF-MEASUREMENT OF BLOOD PRESSURE Measurement of blood pressure outside the clinician’s office may provide valuable information for the initial evaluation of patients with hypertension and for monitoring the response to treatment. Self-measurement has four general advantages: (1) distinguishing sustained hypertension from “white-coat hypertension,” a condition noted in patients whose blood pressure is consistently elevated in the physician’s office or clinic but normal at other times; (2) assessing response to antihypertensive medication; (3) improving patient adherence to treatment; and (4) potentially reducing costs. The blood pressure of persons with hypertension tends to be higher when measured in the clinic than outside of the office. There is no universally agreed-on upper limit of normal home blood pressure, but readings of 135/85 mm Hg or greater should be considered elevated.
Choice of Monitors for Personal Use Although the mercury sphygmomanometer is still the most accurate device for clinical use, it is generally not practical for home use. Therefore, either validated electronic devices or aneroid sphygmomanometers that have proven to be accurate according to standard testing are recommended for use along with appropriatesized cuffs. Finger monitors are inaccurate. Periodically, the accuracy of the patient’s device should be checked by comparing readings with simultaneously recorded auscultatory readings taken with a mercury device. Independent evaluations of the instruments available to patients are published from time to time.AMBULATORY BLOOD PRESSURE MONITORING A variety of commercially available monitors, which are reliable, convenient, easy to use, and accurate, now are available. These monitors typically are programmed to take readings every 15 to 30 minutes throughout the day and night while patients go about their normal daily activities. The readings can then be downloaded onto a personal computer for analysis. Normal blood pressure values taken by ambulatory measurement (1) are lower than clinic readings while patients are awake (below 135/85 mm Hg); (2) are even lower while patients are asleep (below 120/75 mm Hg); and (3) provide measures of SBP and DBP load. In the majority of individuals, blood pressure falls by 10 to 20 percent during the night; this change is more closely related to patterns of sleep and wakefulness than to time of day, as illustrated by the blood pressure rhythm following the inverted cycle of activity in night-shift workers.Among persons with hypertension, an extensive and very consistent body of evidence indicates that ambulatory blood pressure correlates more closely than clinic blood pressure with a variety of measures of target organ damage such as left ventricular hypertrophy. Prospective data relating ambulatory blood pressure to prognosis are limited to two published studies, which suggest that, in patients in whom an elevated clinic pressure is the only abnormality, ambulatory monitoring may identify a group at relatively low risk of morbidity. Ambulatory blood pressure monitoring is most clinically helpful and most commonly used in patients with suspected “white-coat hypertension,” but it is also helpful in patients with apparent drug resistance, hypotensive symptoms with antihypertensive medications, episodic hypertension, and autonomic dysfunction. However, this procedure should not be used indiscriminately such as in the routine evaluation of patients with suspected hypertension. EVALUATION Evaluation of patients with documented hypertension has three objectives: (1) to identify known causes of high blood pressure; (2) to assess the presence or absence of target organ damage and cardiovascular disease, the extent of the disease, and the response to therapy; and (3) to identify other cardiovascular risk factors or concomitant disorders that may define prognosis and guide treatment. Data for evaluation are acquired through medical history, physical examination, laboratory tests, and other diagnostic procedures.Medical History A medical history should include the following:
Physical Examination The initial physical examination should include the following:
Laboratory Tests and Other Diagnostic Procedures Routine laboratory tests recommended before initiating therapy are tests to determine the presence of target organ damage and other risk factors. These routine tests include urinalysis, complete blood cell count, blood chemistry (potassium, sodium, creatinine, fasting glucose, total cholesterol, and high-density lipoprotein [HDL] cholesterol), and 12-lead electrocardiogram.Optional tests include creatinine clearance, microalbuminuria, 24-hour urinary protein, blood calcium, uric acid, fasting triglycerides, low-density lipoprotein (LDL) cholesterol, glycosolated hemoglobin, thyroid-stimulating hormone, and limited echocardiography (to determine the presence of left ventricular hypertrophy). More complete assessment of cardiac anatomy and function by standard echocardiography, examination of structural alterations in arteries by ultrasonography, measurement of ankle/arm index, and plasma renin activity/urinary sodium determination may be useful in assessing cardiovascular status in selected patients. |
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