Ambulatory blood pressure monitoring in the evaluation of antihypertensive drugs.

UNLABELLED

CLINIC VERSUS AMBULATORY BLOOD PRESSURE MEASUREMENT: Clinic blood pressure measurements do not give the best estimate of the efficacy of antihypertensive drugs because (1) they provide readings for one time-point only, (2) they are subject to a 'white-coat' effect and also show a significant placebo effect and (3) they are poorly reproducible. Ambulatory blood pressure monitoring overcomes these problems and offers the possibility of obtaining reliable, reproducible and detailed information on the time-course and magnitude of the effect of antihypertensive treatment on blood pressure over 24 h. MEAN 24-H VERSUS MEAN HOURLY AMBULATORY BLOOD PRESSURE VALUES: Compared with mean 24-h values, reproducibility is poorer for mean hourly ambulatory values, which show greater variability when tested under different conditions. Thus, caution must be exercised when the effects of antihypertensive drugs on hourly blood pressure profiles are analysed and the trough:peak ratio is calculated.

FURTHER PROBLEMS WITH AMBULATORY MONITORING

There are further reasons for caution: (1) ambulatory blood pressure readings can be inaccurate, (2) there is only preliminary information on normal reference values and (3) there have been no longitudinal studies demonstrating the prognostic value of ambulatory blood pressure monitoring, which introduces uncertainty into attempts to evaluate the optimal effect of antihypertensive treatment by this method.

CONCLUSIONS

These limitations do not detract from the use of ambulatory blood pressure monitoring in drug studies, but they do suggest that this measurement technique should not be used routinely for assessing antihypertensive treatment in clinical practice.