[Variability of heart rate in hypertensive patients: clinical and physiopathological implications].

Heart rate variability has been investigated in essential hypertension by studies combining 24-hour ambulatory blood pressure and heart rate monitoring techniques. These studies have shown a clear circadian pattern of heart rate fluctuations. By means of spectral analysis it has also been possible to describe the changes over the 24 hours of specific heart rate fluctuations occurring at various frequencies, which, at least in mild to moderate hypertensives, are not different from those of normotensive subjects. Laboratory studies have also shown the important role exerted by arterial baroreflexes in modulating heart rate variability. Finally, recent methods have been developed to dynamically monitor changes in baroreflex sensitivity in daily life conditions through the time domain or frequency domain analysis of spontaneous blood pressure and heart rate fluctuations.