Comparison of repeated measurement of ambulatory and clinic blood pressure readings in isolated systolic hypertension.

Repeated clinic blood pressure measurement was compared with non-invasive ambulatory blood pressure monitoring in 10 elderly subjects with persistent isolated systolic hypertension and 11 normotensive controls. Mean clinic blood pressures +/- Standard Deviation (SD), at visit 1 were 165/81 +/- 12/7 mmHg and 136/87 +/- 14/10 mmHg respectively. Subjects were assessed on three subsequent occasions at weekly intervals. None were receiving antihypertensive or vasoactive medication. Clinical systolic and diastolic blood pressures were consistently higher than the corresponding mean daytime ambulatory blood pressures in both clinical groups at each of the visits. The difference was greater between the systolic pressures than between the diastolic pressures and these differences in systolic pressures were greater in the isolated systolic hypertensives (26 +/- 5 mmHg) than in the normotensives (7 +/- 18 mmHg). Daytime ambulatory readings aggregated from all four visits were normally distributed for both blood pressure components in both clinical groups. In the isolated systolic hypertension group the clinic systolic and diastolic blood pressure measurements corresponded to the 93rd and 85th percentiles of the ambulatory pressures respectively whereas in the normotensives the equivalent percentiles were 69 and 78. These results suggest a pressor response may largely account for the elevated systolic blood pressure seen in elderly subjects with sustained isolated systolic hypertension based on clinic readings.