Trial of typological classification of the blood pressure profile over 24 hours in aged patients by Fourier analysis

The profiles of 24-hour systolic and diastolic arterial pressures and heart rates obtained with the Bard-Sentron system were studied in 36 untreated subjects (24 women and 12 men, aged from 65 to 89 years) with normal or borderline blood pressure. Each profile was modelized by a Fourier's serie. Multivariate analysis showed that 4 first harmonics were sufficient for a good description of the values observed. A programme of redistribution in subgroups, using McQueen's reallocation method and based on diastolic pressure spectrum, divided the subjects into two groups (A and B) such that the diastolic pressure spectrum of subjects in the same group were "similar" and those of subjects in different groups were "dissimilar". Subjects in both groups were of the same age and had the same man/woman ratio. The diastolic profile of group A showed marked day-night variations, while that of group B had almost the same level day and night. The same method can be applied to systolic pressure. Although the exact role of ambulatory blood pressure as a risk factor remains to be determined, a strong day-night variation of pressure observed in a given subject ought to be closely watched by the clinician. This study suggests a method to evaluate the different types of arterial pressure and heart rate profiles in any population of subjects and to identify a group at higher cardiovascular risk, if it is present.