EVALUATION OF THE CHANGE IN CARDIAC AUTON OMIC NERVOUS-SYSTEM ACTIVATION WITH AGED CLINICAL AND MEASUREMENT BY AUTOMATIC

The object of this study was to establish normal values for age of cli nical tests of autonomic nervous system activity based on an automatic measuring system. Nenety-seven subjects (50 M/47 F) aged 20 to 85 yea rs (average 45 +/- 13 years) with a normal clinical examination and no medication were included in the study. The blood pressure (BP) and he art rate (HR) were measured continuously with the Finapres system. Aft er a resting period, the BP and HR were measured continuously in 5 dif ferent situations : dorsal decubitus position for 7 minutes ; on getti ng up actively in less than 3 seconds and for 9 minutes in the upright positions, during deep brething at 6c/min and Valsalva manoeuvre duri ng a handgrip test at 30 % of maximal voluntary strength for 3 minutes . A specific programme (ISN-CNRS) initiated the calculations of the te st and preformed direct and crossed spectral analysis in the lying and standing positions. The average BP was 120 +/- 18/66 +/- 11 mmHg and HR was 67 +/- 9 b/min. A negative linear correlation was observed with age with respect to the 3 tests investigating vagal activity : 30/15 ratio, spontaneous variations of respiration and HR, ratio of HR at th e end of Valsalva with r = - 0.43, r = - 0.60, r = - 0.34 (p < 0.001). The other two tests : variation of systolic BP 1 min 30 after standin g and variation of diastolic BP during the handgrip did not change wit h age. The study of stationary variability by spectral analysis showed the same change with age on the variability of HR (r = - 0.40, p < 0. 001), whereas the variability in BP did not change significantly. The modulus of the transfer function between systolic BP and HR (equivalen t of gain in baroreflex) decreased significantly with age (r = - 0.34, p < 0.001). These results show that the alteration of baroreflex cont rol with age can be demonstrated by single clinical tests using the Fi napres system. For diagnosis, reference values are required. The absen ce of significant changes of variability of the BP with age emphasises the limits of laboratory investigations.