Ambulatory blood pressure measurement in the elderly

Abstract

A number of problems relating to clinic measurements of blood pressure may be particularly relevant to elderly patients with isolated systolic hypertension. First, there are large discrepancies in the blood pressure levels measured by these two techniques in the elderly population. Second, while blood pressure is universally accepted as one of the most important risk factors for the development of cardiovascular morbidity, its predictive value in the individual is relatively poor. Clinic and 24-h ambulatory recordings from 318 patients aged 17-80 years, diagnosed as having isolated systolic hypertension on clinic measurement, were compared with reference values determined from 815 healthy bank employees. In the isolated systolic hypertension group, mean systolic blood pressure by daytime ambulatory measurement was 27mmHg lower than that recorded in the clinic, while diastolic pressure was similar (151 ± 17/87 ± 11 versus 178 ± 28/84 ± 9mmHg). This discrepancy was greater in women than men, increased slightly but significantly with age (r = 0.12, P<0.05) and raised the crucial question as to which of the two measurements might best predict prognosis in this population. In a further study of the association between electrocardiographic (ECG) voltages and blood pressure measured in the clinic and by ambulatory monitoring in 216 patients with isolated systolic hypertension, the sum of SV1 + RV5 and the sum of SV1 + RV6 were significantly and positively related to systolic pressure both in the clinic and with daytime and night-time ambulatory measurement. In addition, we calculated residual ambulatory blood pressure, defined as the difference between the observed ambulatory blood pressure and the blood pressure predicted from the linear regression equation relating clinic blood pressure to the blood pressure on ambulatory measurement, to determine whether ambulatory blood pressure measurement improved the estimate of ECG voltages based on the clinic measurement alone, and we found that most of the correlations remained significant. There are marked discrepancies between blood pressure measured in the clinic and with ambulatory blood pressure monitoring in elderly patients with isolated systolic hypertension. While both methods predicted left ventricular hypertrophy as assessed by ECG voltage criteria, the ambulatory measurement added further accuracy to the prediction of left ventricular hypertrophy already provided by the clinic measurement. These findings require confirmation in a prospective trial such as the secondary project on ambulatory monitoring in the Syst-Eur Study.