[Clinical implications of blood pressure variability]

There are many variations in blood pressure, ranging from that observed between systole and diastole (pulse pressure) to slower daily or seasonal variations. This variability has many facets, for example the simple concept of variation around the mean blood pressure and the more complex spectral, chaos or fractal analysis... Some of these concepts are still the subject of fundamental research and have no current clinical applications. Others, however, are already part of our evaluation of hypertensive patients or used as prognostic factors in cardiac failure or myocardial infarction. Blood pressure variability, either the pulse pressure or 24 hour variability, is associated with a higher incidence of cardiovascular complications. Although the causality of the relationship is uncertain, patients with the greatest variability seem to be at higher risk. In addition to this prognostic impact, the study of changes in blood pressure by spectral analysis may also provide indices of adrenergic tone or sympathovagal equilibrium which may be useful clinically. Finally, the combined study of blood pressure variability and heart rate lead to the baroreflex, the sensitivity of which integrates major risk factors such as blood pressure, age, heart rate and serum cholesterol. This baroreflex could be a useful parameter for stratification of cardiovascular risk. This has already been demonstrated in patients at high risk, such as those with cardiac failure or myocardial infarction.