The adverse effects of hypertension are most probably related to the overall level of pressure to which the circulation is exposed, and it is reasonable to suppose that an individual patient whose blood pressure (BP) is elevated for most of the time has a worse prognosis than one whose BP is elevated only occasionally. A visit to a physician's office for evaluation of BP may itself elevate the pressure, but the recording of a high BP by the physician does not necessarily mean that such an elevation is permanent. Blood pressure readings were taken every 15 minutes using a noninvasive ambulatory BP recorder during 24 hours in 25 subjects with normal BP, 25 with borderline hypertension, and 25 with established essential hypertension. Readings were analyzed for four situations: (1) physician's office, (2) work, (3) at home and (4) asleep. Treadmill exercise tests were also performed on a separate occasion with the Bruce protocol. The 24-hour recording in all three groups showed the highest BPs at work and the lowest during sleep. The situational BP changes were generally similar, but both hypertensive groups differed from normal subjects in that they showed consistently higher BPs in the physician's office than at home, whereas normal subjects showed little difference. During exercise, the hypertensive groups showed a similar rise of systolic pressure to that of normal subjects. Pressures recorded in the physician's office gave good predictions of the average 24-hour pressure in normal and established hypertensive subjects, but not in the borderline group; in such patients, 24-hour monitoring may be of particular value in establishing the need for treatment.
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