Prognostic data on short-term blood pressure variability derived from 24-hour ambulatory monitoring are still limited, even though the prognostic value of long-term visit-to-visit variability in blood pressure seems to be established. The main objective of this study is to assess the prognostic value of blood pressure variability based on 24-hour ambulatory blood pressure measurements, independent of ambulatory central pressure, in the Bordeaux cohort of hypertensive patients.
Design and method:
We included a total of 914 patients in our study, with an average age of 54 ± 14 years. To be included, subjects had to have undergone 24-hour ambulatory blood pressure monitoring at baseline with four hourly measurements day and night and accurate determination of their wake-up time and bedtime. Patients were followed for 120 ± 78 months on average, during which we recorded 163 cardiovascular events and 58 deaths.
In the univariate survival analysis, only the standard deviations of day and nighttime systolic blood pressure (SBP), and day, night and 24-hour heart rate (HR) were found to be associated with occurrence of cardiovascular events. Among these parameters, the standard deviations of night SBP and 24-hour heart rate variability showed the strongest association with the outcome variable. We used the ratio of nighttime SBP SD to 24-hour HR SD as the main variable explanatory for the multivariate survival analysis. In these analyses, the predictive value of variability remains significant with the introduction of major cardiovascular risk factors and average 24-hour SBP, but disappears when 24-hour central pulse pressure is included in the model.
In conclusion, the variability of the nocturnal systolic blood pressure determined by 4-hourly ambulatory measurements over 24 hours and heart rate variability are significantly associated with the occurrence of cardiovascular events, independently of average 24-hour systolic blood pressure. However, the significance of this relationship disappears when central pulse pressure is considered.