Quantitative sympathetic evaluation in hypertensive elderly patients.

Guzzetti et al. proved that the hypertensive adult subjects show an increase of the sympathetic activity. We evaluated the behaviour of sympathetic activity by the autoregressive power spectral analysis, calculated by computerized R-R variability. Two major components are contained in power spectral density: a low frequency (LF) (from 0.04 to 0.15 Hz) and a high frequency (HF) (from 0.16 to 0.40 Hz). Surgical and pharmacologic study showed that the LF is determined by sympathetic tone, instead the HF is determined by the vagal tone. During tilt LF increases while HF decreases. We compared the change of power of spectral after tilting in 5 hypertensive elderly subjects (H) (age: 79.2 ± 6.5) and 3 healthy elderly (E) (age: 70.3 ± 4.1). The power is expressed in normalized units (nu) obtained by dividing the power of a given component by the total variance and multiplying by 100. Results are summarized in the table: LF nu(t) = Lf nu after tilting, HF nu(t) = Hf nu after tilting. (* p< 0.001: H vs. E, baseline vs. tilt) Aging induces a decrease of sympathetic tone and this phenomena is higher in hypertensive elderly subjects.