Isolated Elevation of Diastolic Blood Pressure

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Abstract
Abstract Not infrequently, blood pressure measurement by the standard auscultatory technique yields a normal systolic pressure with an elevated diastolic pressure. The relatively narrow pulse pressure of such a measurement raises concern about the accuracy of the blood pressure measurement. The purpose of this study was to assess the accuracy of auscultatory blood pressure measurements in patients with an uncommonly narrow pulse pressure, particularly patients with an elevated diastolic but normal systolic pressure. Auscultatory blood pressure measurements were compared with an objective noninvasive standard, called K2 analysis, which has been shown to be more accurate than the auscultatory technique. Blood pressure was measured simultaneously by auscultatory and K2 techniques in 175 subjects. Comparisons were performed (1) in the group as a whole, (2) in four clinical subgroups (normotensive [P <.0004). For systolic pressure, differences were less than 3 mm Hg in all four clinical groups. Auscultatory-K2 differences of diastolic pressure exceeding 5 mm Hg (and 10 mm Hg) were seen in 73.3% (and 40.0%) of isolated diastolic hypertensive subjects versus only 14.5% (2.9%) of normotensive subjects, 22.6% (1.9%) of hypertensive subjects, and 7.9% (2.6%) of isolated systolic hypertensive subjects ( P <.0001). Similarly, the auscultated diastolic pressure exceeded the K2 measurement by at least 5 mm Hg (and 10 mm Hg) in 62.5% (29.2%) of subjects with a pulse pressure ratio less than 0.45 versus 13.9% (2.0%) in subjects with a ratio greater than or equal to 0.45 ( P <.0001). Auscultatory-K2 differences of diastolic pressure were strongly and inversely related to the pulse pressure ratio ( r =−.68, P <.0001) independent of sex, race, or body weight. In conclusion, when the pulse pressure is particularly narrow, auscultation frequently overestimates the true diastolic pressure by 5 mm Hg or more. The treatment implications of this finding, particularly in patients with elevated diastolic but normal systolic pressure, merit further study.