J. Cox

Ambulatory blood pressure monitoring in elderly patients with isolated systolic hypertension

Objectives: This study compared clinic and ambulatory blood pressure measurement and the reproducibility of these measurements in older patients with isolated systolic hypertension (ISH). Patients: Eighty-seven patients aged ≥60 years with ISH on clinic measurement were followed in the placebo run-in phase of the Syst-Eur trial. Methods: Clinic blood pressure was defined as the mean of two blood pressure readings on each of three clinic visits (six readings in total). Ambulatory blood pressure was measured over 24 h using non-invasive ambulatory blood pressure monitors. Results: Daytime ambulatory systolic pressure was, on average, 21 mmHg lower than the clinic blood pressure, whereas diastolic pressure was, on average, similar with both techniques of measurement. In the 42 patients who had repeat measurements, clinic blood pressure levels and the amplitude of the diurnal blood pressure profile (fitted by Fourier analysis) were equally reproducible. However, both were less reproducible than ambulatory blood pressure levels. The repeatability coefficients, expressed as per cent of near maximum variation (four times the standard deviation of a given measurement), were 52% and 45% for the clinic systolic and diastolic pressures, 56% and 42% for the amplitude of the diurnal profile, and 29% and 26% for mean 24-h pressures. Conclusions: In older patients with ISH, clinic and ambulatory systolic blood pressure measurements may differ largely: the prognostic significance of this difference remains to be elucidated. Furthermore, in these patients the level of pressure is more reproducible by daytime ambulatory blood pressure measurement than by clinic measurement.

Cumulative sums in quantifying circadian blood pressure patterns.

The plotting of cumulative sums (cusums), a technique of proven value in the detection of trends in data collected at intervals of time, may be modified to analyze circadian blood pressure patterns quantitatively. Mean 24-hour ambulatory blood pressure is taken as the reference value and is subtracted from each pressure value. The products of the remainders and the corresponding time intervals are summed in sequence and are plotted against time to form a modified cusum plot. The slope of the plot over any given time period equals the difference between mean blood pressure during that period and mean 24-hour blood pressure. Crest and trough blood pressures (the mean blood pressures of the 6-hour periods of highest and lowest pressures) may be identified as the 6-hour periods where plot slopes are most steeply ascending and descending, respectively. The magnitude of the circadian blood pressure change, defined as the difference between crest and trough blood pressure, is calculated from the difference between crest and trough plot slopes. The height of the cusum plot, which reflects pressure alteration extent and duration, may also be used as a measure of circadian pattern. The modified cusums technique and cusum-derived statistics are illustrated using ambulatory blood pressure profiles of hypothetical and actual hypertensive subjects. Independence from fixed time periods improves precision and reproducibility. Cusum-derived statistics are simply calculated from raw ambulatory data and should prove useful in the quantitative analysis of circadian blood pressure profiles.

Ambulatory blood pressure measurement in the evaluation of blood pressure lowering drugs.

Since the indirect m e h r e m e n t o f hlood pressure based o n the principle of arterial occlusion using a forearm cuff was introduced by Scipione Kiva-Rocci in 1896 111 and subsequently nlodifiecl t o incorporate auscultation by Nicolai Korotkolf in 1905 (21, this technique h:a been the universal method used in the assessment of blood pressure in medial practice. Most of the evidence showing that the antihypertensive drugs in everyday use lower blood pressure derives from studies of clinic blood pressure measured by this technique 13-51. However, it is well known that casual blood pressure measured in the clinic may be influenced by a number of factors and as long ago as 1904, Theodore Janeway, writing before Korotkoff had reported the now accepted auscultatory method of measuring blood pressure, showed that stress could raise blood pressure 161.

Twenty-four hour blood pressure monitoring in the Syst-Eur trial

This article describes the objectives and protocol of a study on ambulatory blood pressure in elderly patients with isolated systolic hypertension. This study constitutes an optional side-project to the Syst-Eur trial.The multicentre Syst-Eur trial investigates whether antihypertensive treatment of elderly patients with isolated systolic hypertension will influence the incidence of stroke. Secondary endpoints include cardiovascular events, such as myocardial infarction.The main objective of the side-project is to investigate whether ambulatory blood pressure monitoring will improve the prediction of cardiovascular complications based on blood pressure measurement in the clinic. The side-project also provides the opportunity to evaluate the diurnal profile of blood pressure in elderly patients with isolated systolic hypertension randomized to placebo or active antihypertensive treatment.

Relationship between blood pressure measured in the clinic and by ambulatory monitoring and left ventricular size as measured by electrocardiogram in elderly patients with isolated systolic hypertension

Objective: To assess the additional diagnostic precision conferred by ambulatory blood pressure monitoring on clinic blood pressure measurement in evaluating the severity of isolated systolic hypertension. Methods: The association between left ventricular size as determined by ECG voltages [R-wave voltages in lead V5 (RV5) and S-wave voltages in lead V1, (SV1,)] and blood pressure as assessed by clinic measurements and ambulatory blood pressure monitoring was studied in 97 elderly patients included in the placebo run-in phase of the Syst-Eur trial. The additional diagnostic precision conferred by ambulatory monitoring on clinic blood pressure measurements was assessed by relating the residual ambulatory blood pressure level to the ECG-left ventricular size. The residual ambulatory blood pressure level was calculated by subtracting the predicted ambulatory blood pressure level for each patient (using the linear regression equation relating both techniques for the group) from the observed ambulatory blood pressure. Results: Clinic systolic blood pressure was on average 20mmHg higher (P<0.001) than daytime ambulatory blood pressure while diastolic blood pressure was similar with both techniques. The sum of SV1 + RV5 was significantly related to clinic systolic pressure (r=0.25), and 24-h (systolic, r=0.37; diastolic, r=0.29), daytime (systolic, r=0.30; diastolic, r=0.19) and night-time (systolic, r=0.33; diastolic, r=0.28) ambulatory blood pressure levels. These findings were not affected by adjustment for gender, age and the body mass index. The sum of SV1 + RV5 was significantly related to the residual 24-h (systolic, r=0.30; diastolic, r=0.31), daytime systolic (r=0.20) and night-time (systolic, r=0.31; diastolic, r=0.29) ambulatory blood pressure monitoring levels. Conclusion: Ambulatory blood pressure monitoring adds to the diagnostic precision of clinic blood pressure measurement in assessing the severity of hypertension in this population. The ongoing side project on ambulatory blood pressure monitoring in the Syst-Eur study should establish whether these findings hold true for morbidity and mortality.

Further learnings from the European Working Party on High Blood Pressure in the Elderly (EWPHE) study: Focus on systolic hypertension

SummaryEvent rates in relation to the number of elderly hypertensives treated were calculated from randomized analysis data from the 840 patients who completed the European Working Party on High Blood Pressure in the Elderly (EWPHE) trial. In all, the actively treated group had 29 fewer cardiovascular events per 1000 patient years. Putting this another way, treating 34 patients for 1 year would prevent one cardiovascular event. Moreover, as there were 14 fewer cardiovascular deaths and 11 fewer nonfatal strokes per 1000 patient years in the actively treated groups, we calculated that treating 71 or 91 elderly patients for 1 year would prevent one cardiovascular death or nonfatal stroke, respectively. Because of the higher baseline incidence of cardiovascular events in this study, there were greater gains in terms of absolute reductions in mortality and morbidity in treated elderly hypertensive patients than in younger patients in similar studies. Of the 840 patients who participated in the trial, 247 had systolic blood pressure>-160 mmHg and diastolic blood pressure <-95 mmHg. In this group, blood pressure was reduced by 13/8 mmHg after 3 years in those randomized to active treatment compared to placebo. While patient numbers were insufficient to draw firm conclusions, their outcome on treatment was similar to that for patients on active treatment in the overall study. These results highlight the need for a rigorous assessment of the value of treating isolated systolic hypertension in the elderly.

Does isolated systolic hypertension occur with ambulatory blood pressure measurement

Ofice and 24-h ambulatory blood pressure measurements in 815 healthy subjects, who were employees of the Allied Irish Bank [3], were taken as reference values. Data on 318 patients, referred to the Blood Pressure Unit at Beaumont Hospital and diagnosed as having isolated systolic hypertension (clinic systolic pressure equal to or greater than 160 mmHg and diastolic pressure equal to or less than 94mmHg) were analysed. The group was further subdivided into those on and off medication at the time of the blood pressure measurement.