[Ambulatory measurement of blood pressure]

The advent of new techniques has greatly contributed to the development of ambulatory measurement as a noninvasive method for evaluating blood pressure. The technique implies use of a validated and reliable standardized apparatus. The operator must strictly comply with operating procedures, which must also be explained to the patient. Ambulatory measurement can be meaningful only if the results are compatible with reference values, which have now been established, and if the causes of possible error can be recognized and interpreted. Ambulatory blood pressure measurement has greatly improved our knowledge of physiological and pathological variations over the circadian cycle including day/night variability and the effects of psychosensorial stimulation. Diagnostic indications are clearly identified and include borderline hypertension suspected but not identified after about 3 months, the white coat effect, severe hypertension when modifications in the circadian cycle are suspected, paroxysmal hypertension, suspected pheochromocytoma, and gravid hypertension or an inversion of the circadian cycle possibly preceding an episode of eclampsia. There are also a certain number of particular indications in patients with degenerative or primary conditions affecting their autonomy. The true prognostic value of these recordings was recognized several years ago and has been confirmed by clinical trials. For example, the white blouse effect has no significant implication in terms or predicting less favourable morbidity or mortality. Finally, ambulatory blood pressure measurement has been definitively shown to be a valid method for evaluating the therapeutic effect of an anti-hypertensive drug in a given patient, especially when resting levels are questioned. For therapeutic trials, ambulatory measurements serve as a reference to evaluate the effect of treatment on the circadian cycle. Peak/dip levels can thus be determined in comparison with the residual effect of the drug. A large number of studies remain to done to identify the full potential of this method.