Beta-blockers vs. thiazides in the treatment of hypertension: a review of the experience of the large national trials.

The effects of antihypertensive treatment on cerebrovascular disease and coronary artery disease (CAD) end points reported in the large-scale national trials have differed. All trials have shown stroke benefit, whereas CAD benefit has not been convincingly demonstrated in any. In three trials, the effects of thiazide- and beta-blocker-based regimens can be directly compared. In the MRC Treatment Trial for Mild Hypertension in Britain, the largest of the trials and the only one to compare these two classes of drugs with each other and with untreated controls, stroke benefit was significantly greater in the thiazide than in the beta-blocker group (p = 0.002). Indeed, the 70% reduction in fatal strokes and 65% reduction in nonfatal strokes suggested an effect on cerebral infarction as well as on cerebral hemorrhage. Opposing trends were found for CAD end points with beta-blockers and thiazides when compared with controls. For coronary events, sudden deaths, and ECG changes of infarction, significant differences were found between the reduced rates for those receiving propranolol and the higher rates for those receiving bendrofluazide. Weak evidence has been put forward by four trials-MRFIT, HDFP, the Oslo trial, and the MRC trial-suggesting that thiazide treatment for those who already have evidence of coronary disease may be harmful. In no case is the evidence conclusive, and it involves only a small (but important) subgroup. In the MRC trial, a nonselective beta-blocker, propranolol, provided greater CAD benefit as measured by the incidence of myocardial infarction, sudden death, and ECG changes, but only in nonsmokers. Hypotheses generated by these trials need further investigation.

Further results of the MRC treatment trial for mild hypertension.

17,354 mildly hypertensive adults with diastolic (v) pressures of 90-109 mm Hg took part in a 5 1/2 year trial in which each was randomized to treatment with either bendrofluazide, propranolol, or placebo. The main results of the trial have been published; they showed stroke benefit but no overall reduction in the incidence of coronary events and no effect on all-cause mortality. Further analyses of the data have shown interesting differences between subgroups of the population, with regard to the effects of the two types of treatment on stroke, on coronary events and on ECG changes. These results, and the effects of interaction between cigarette smoking and the efficacy of these drugs, if confirmed in other studies, should influence the choice of drug therapy for mild hypertension.

Effects of diuretic and beta-blocker therapy in the Medical Research Council Trial.

The Medical Research Council's treatment trial for mild hypertension was designed to determine the effects of blood pressure reduction on cardiovascular morbidity and mortality rather than to compare the separate effects of thiazides and beta-adrenergic blocking agents. However, the simultaneous use of both active treatments was discouraged and comparisons in terms of blood pressure control, adverse drug reactions, and drug-related changes in the serum biochemistry are possible. The net differences in systolic and diastolic pressure between treated and control subjects were greater in older than in younger people; this net difference was more pronounced in the older people assigned at random to receive bendrofluazide as opposed to propranolol; this effect increased with time during the trial. The need for a supplementary drug (methyldopa) to control blood pressure at target level, was greater in the thiazide-treated group for all ages. Withdrawal from randomized treatment due to adverse reactions was greater in men receiving bendrofluazide than in those receiving propranolol, and greater for women receiving propranolol than in those receiving bendrofluazide. Thiazide treatment was shown, in a sub-study, to be associated with a significant increase in ventricular ectopic activity in long-term participants.

Evaluation of the Vita-Stat automatic blood pressure recorder. A comparison with the Random-Zero sphygmomanometer.

A total of 408 adult volunteers at Northwick Park Hospital, England, participated in an evaluation of the Vita-Stat automatic blood pressure (BP) recorder. During a five-day period in March 1981, readings of BP obtained by two Vita-Stat machines were compared with measurements obtained by two trained observers using Random-Zero sphygmomanometers. The order in which BP readers were obtained was randomized. A significant effect of order on systolic BP was removed from comparisons between techniques. For diastolic BP values, there was close agreement between the different measurement techniques and each was associated with a similar degree of repeatability between duplicate recordings. In contrast, both Vita-Stat machines seriously overestimated systolic BP and there was substantially more variability between duplicate readings of systolic BP obtained with the Vita-Stat machines than for Random-Zero values. The use of either Vita-Stat machine for population screening would have correctly identified almost all those with a high BP but would have led to considerable overdiagnosis of systolic hypertension. Despite their limitations, the accuracy of diastolic BP estimates and considerations of cost and convenience suggest that Vita-Stat machines might be useful as initial screening tools for detection of persons with high diastolic BP. However, the use of a particular Vita-Stat machine should be preceded by an evaluation of the machine against a standard method of BP estimation.

Seasonal variation in arterial blood pressure.

Blood pressure measurements recorded during the medical Research Council's treatment trial for mild hypertension have been analysed according to the calendar month in which the readings were made. For each age, sex, and treatment group systolic and diastolic pressures were higher in winter than in summer. The seasonal variation in blood pressure was greater in older than in younger subjects and was highly significantly related to maximum and minimum daily air temperature measurements but not to rainfall.

Systolic or diastolic hypertension--which matters most?

Blood pressure was recorded in 2680 people over a period of 17 years. Of 685 deaths, 250 occurred in men over 65 and 148 (58%) were attributed to cardiovascular causes. 219 women over 65 died; 157 (72%) from cardiovascular causes. For both sexes chi-square values relating death to systolic blood pressure were higher than the values for diastolic pressure. (Ed.)

Bacteriuria and subsequent mortality in women.

The relation of bacteriuria to subsequent mortality was investigated in population-based cohort data from women living in Jamaica and Wales. Three surveys were done in each location over a 13-year period. Women with 10(5) or more gram-negative bacilli per millilitre of urine in three consecutive cultures over a 3-week span were considered bacteriuric for that survey. Mortality was determined at the second and third surveys. Bacteriuria was associated with increased mortality both in the crude data and in life-table analyses adjusted for the confounding effects of age and weight. The adjusted risk ratio for death between the first and third surveys was 1.5 for women bacteriuric at the first survey compared with non-bacteriuric women. For deaths between the second and third surveys, the adjusted risk ratio was highest (2.0) in women who were bacteriuric at both of the first two surveys. The adjusted risk ratio for death between the second and third surveys for women who were bacteriuric at one of the first two surveys but not at the other was 1.6.

A comparison of cardiovascular measurements in the Gambia, Jamaica, and the United Republic of Tanzania.

Epidemiological studies of the cardiovascular characteristics of three typically rural communities in the Gambia, Jamaica, and the United Republic of Tanzania were carried out by means of standardized methodology. This paper reports comparisons of arterial blood pressure distribution and electrocardiographic findings in relation to age, sex, and body build. Marked differences in blood pressure were found, with higher values in Jamaicans than in Tanzanians, who in turn had higher values than Gambians. These differences are not explicable in terms of body build. Heart rates and ECG amplitudes were also strikingly different, with higher values in Jamaicans than in Tanzanians and Gambians. The differences in ECG amplitudes cannot be explained by differences in body build, heart rate, or blood pressure. The findings agree with the hypothesis that some factor or factors associated with development contributes to the risk of cardiovascular disease in peoples of African origin.