[Sinus variability: value of rhythmology]

The study of heart rate variability is a mean of assessing the influence of the autonomic nervous system on the normal and pathological heart. It may be performed by temporal or spectral analysis over 24 hours or shorter periods. It is possible to define for each temporal or spectral analysis the components of the autonomic nervous system which influence these parameters. After myocardial infarction a decrease in heart rate variability indicates a poor prognosis. This post-infarction risk factor is relatively reliable compared with the other prognostic factors. A decreased heart rate variability is also observed in cardiac failure but the significance of this finding has not been established. Many other fields of application of the study of heart rate variability may be envisaged, in other cardiovascular pathologies, in the evaluation of cardiovascular therapeutic interventions or in the assessment of patients with non-cardiac pathology in which the autonomic nervous system plays an important role. A lot of research on heart rate variability is currently under way and many developments are expected in the next few years.