Rate of blood pressure changes assessed by 24 h ambulatory blood pressure monitoring: another meaningful index of blood pressure variability?

Abstract

Data collected over the past 60 years, thanks to the introduction of ambulatory blood pressure monitoring (ABPM) techniques, have clearly shown that blood pressure (BP) is a highly variable parameter [1]. Such a solid awareness, however, has not found a suitable translation into clinical practice yet, and the evaluation of BP-related cardiovascular risk is still largely confined, in the best case, to the assessment of average BP values from a series of measurements (obtained by ambulatory or home BPM), while most recommendations related to hypertension management are still based on isolated clinic measurements [2,3]. This despite the availability of growing evidence that BP variability is an independent predictor of organ damage and cardiovascular events [4– 9]. A few reasons may explain the difficulties in introducing BP variability as a routine clinical tool. One, the complex nature of the mechanisms underlying an increase in BP excursions makes the clinical interpretation and practical use of estimates of BP variability difficult. Indeed, an increased amplitude and frequency of BP fluctuations may reflect alterations of different factors involved in cardiovascular control such as impairment of autonomic or hormonal regulation, renal dysfunction, and increased arterial stiffness [10]. Two, the lack of solid evidence supporting the efficacy of any specific treatment in reducing BP variability is associated with the even more important lack of evidence, except for a few animal studies [11], that its reduction may be actually beneficial in reducing cardiovascular risk. Three, the fact that simple conventional estimates of BP variability based on the calculation of 24 h, daytime or night-time standard deviation (SD) of either systolic or diastolic average BP, even if independently related to outcome, appear to have a rather limited predictive power compared to other more traditional risk factors [4–7,12]. Four, the awareness that the SD of BP average values, com-