Blood pressure variability over 24 hours: its different components and its relationship to the arterial baroreflex

This paper describes several different methods for the analysis of blood pressure and heart rate variability over the 24 hours, both in the time and in the frequency domain. The mechanisms possibly involved in the genesis of the variations in blood pressure and heart rate which occur over a 24-hour period are also discussed. Finally, new approaches to the dynamic evaluation of the sensitivity of baroreflex control of heart rate and of its changes over the 24 hours in daily life conditions, based on computer analysis of the interaction between fluctuations in blood pressure and heart rate, are described. Data obtained by applying these methods in different clinical conditions (normotensive vs. hypertensive subjects, young vs. elderly individuals and pure autonomic failure patients) are presented.