Power spectral analysis of spontaneous blood pressure and heart rate variability in elderly hypertensives.

Abstract

To examine the influence of hypertension on cardiovascular variability in elderly subjects, we measured spontaneous beat-to-beat blood pressure (BPV) and heart rate variability (HRV) in elderly subjects with or without hypertension at rest and during tilting. The study group consisted of 23 community-dwelling, male elderly subjects (aged 62-75 years) and was divided into two groups, i.e., a hypertensive group (HT group; n = 11) and normotensive group (NT group; n = 12). According to the modeling and decomposing algorithm of an autoregressive process, we estimated the component power of low-frequency (LF; 0.03-0.15 Hz) and high-frequency components (HF; respiratory frequency) of BPV and HRV by power spectral analysis. We also measured plasma norepinephrine (PNE) levels in the two groups at rest and during tilting. In the HT group, we found that the amplitude of LF-BPV was greater (p < 0.05) and its relative change by postural tilting was smaller (p < 0.05) than those in the NT group. We found no significant difference in the amplitude of LF-HRV and HF-HRV between the two groups, and found no significant response of the amplitude of LF-HRV and HF-HRV to postural tilting. We also found no difference in PNE level between the two groups at rest or during tilting. These results suggest that the regulatory function of sympathetic vasomotor activity assessed by power spectral analysis of BPV is altered in hypertensive elderly subjects, although the influence of hypertension on the autonomic control of the heart is less dominant in the elderly.