Age-dependent Relationship
between the Carotid Intima-Media Thickness, Baroreflex
Sensitivity, and the Inter-Beat Interval in Normotensive and
Hypertensive Subjects
R. LÁBROVÁ, N. HONZÍKOVÁ1, E.
MADĚROVÁ, P. VYSOČANOVÁ,
Z. NOVÁKOVÁ1, E. ZÁVODNÁ1, B. FIŠER1,
B. SEMRÁD
Department of Internal Cardiology, Faculty Hospital, and 1Department
of Physiology, Faculty of Medicine, Masaryk University, Brno,
Czech Republic
Received February 15, 2005
Accepted May 4, 2005
Summary
The interrelationship between baroreflex sensitivity expressed
in ms/mm Hg (BRS) or in Hz/mm Hg (BRSf), carotid wall thickness
(IMT), and age was investigated in hypertensive and normotensive
subjects with respect to the mean inter-beat interval (IBI) and
blood pressure (BP). BP monitoring was performed in 25 treated
hypertensives (Hy; 47.4±9.2 years of age) and 23 normotensives
(Norm; 44.5±8.1 years). IMT was measured by ultrasonography. BRS
and BRSf were determined by the spectral method (five-minute
non-invasive beat-to-beat recording of BP and IBI, Finapres,
controlled breathing at a frequency of 0.33 Hz). Significant
differences between Hy and Norm were detected in IMT (Hy:
0.624±0.183, Norm: 0.522±0.070 mm; p<0.01), BRS (Hy: 3.5±1.6,
Norm: 5.7±2.3 ms/mm Hg; p<0.01), BRSf (Hy: 0.005±0.002, Norm:
0.009±0.004 Hz/mm Hg; p<0.01), systolic BP (Hy: 131±21, Norm:
116±17 mm Hg; p<0.01) and diastolic BP (Hy: 77±16, Norm: 64±12
mm Hg; p<0.01). A significant correlation was found between age
and IMT (Norm: 0.523, p<0.05; Hy+Norm: 0.419, p<0.01), age and
BRS (Norm: -0.596, p<0.01; Hy+Norm: -0.496, p<0.01), age and
BRSf (Norm: -0.555, p<0.01; Hy: -0.540, p<0.01; Hy+Norm: -0.627,
p<0.01), age and IBI (Hy: 0.478, p<0.05), age and diastolic BP
(Hy: -0.454, p<0.05), BRS and IMT (Hy+Norm: -0.327, p<0.05) and
BRSf and IMT (Hy+Norm: -0.358, p<0.05). Hypertensive patients
have increased IMT and decreased BRS and BRSf. The positive
correlation between age and IMT and the negative correlation
between age and BRS and BRSf are in agreement with the
hypothesis that the age-dependent decrease of baroreflex
sensitivity corresponds to the age-related structural changes of
the carotid wall. Using two indices of baroreflex sensitivity,
BRS and BRSf, we could show that baroreflex sensitivity in
hypertensives is lower not only due to thickening of the carotid
wall, but also due to aging.
Key words
Intima-media thickness • Baroreflex sensitivity • Hypertension •
Age • Heart rate
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