New insight into the mechanism of cardiovascular dysfunction in the elderly

Transfer function analysis

Hong Guo, Frederic Schaller, Nancy Tierney, Scott A. Smith, Xiangrong Shi

Research output: Contribution to journalArticleResearchpeer-review

3 Citations (Scopus)

Abstract

This study sought to test the hypothesis that alterations in the relationships between (i) mean arterial pressure (MAP) and heart rate (HR), (ii) cardiac output (CO) and MAP, and (iii) total peripheral resistance (TPR) and MAP variability contribute to the diminished dynamic control of cardiovascular function with advanced age. Six-minute hemodynamic data were continuously recorded in 11 elderly (70 ± 2 years) and 11 young (26 ± 1 year) healthy volunteers under supine resting condition and during lower body negative pressure-induced orthostatic challenge. The data were converted using fast Fourier transform, and the ratio of cross-spectra to auto-spectra between two signals (i.e., MAP-HR, CO-MAP, TPR-MAP) was computed for transfer function analysis. In the low-frequency ranges (LF; 0.04-0.14 Hz) and high-frequency ranges (0.15-0.30 Hz), the gain and coherence of the transfer function describing the relationship between MAP-HR signals were significantly greater in younger than in older adults. The phase degree was significantly >0 in both groups under all conditions, suggesting that the MAP variability preceded the HR variability. In contrast, the coherence between CO-MAP signals in both age groups was <0.5, indicating that the beat-to-beat MAP variability was not significantly related to the CO signals. However, the transfer function gain and coherence of TPR-MAP signals were significantly greater in the young group (coherence ≥0.5 in the LF range), suggesting a more effective dynamic vasomotor control. In conclusion, the oscillations in CO-MAP signals are not significantly synchronized or not related in a simply linear fashion in both age groups. The MAP variability is more related to the oscillation of TPR signals in the young group only. Advanced age not only diminishes MAP-HR transfer function gain, but also weakens its coherence. Thus, alterations in the relationship between MAP-HR variability and TPR-MAP variability may significantly contribute to the diminished dynamic control of cardiovascular function manifest in the elderly.

Original languageEnglish
Pages (from-to)549-557
Number of pages9
JournalExperimental Biology and Medicine
Volume230
Issue number8
DOIs
StatePublished - 1 Jan 2005

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Transfer functions
Arterial Pressure
Cardiac Output
Vascular Resistance
Heart Rate
Age Groups
Lower Body Negative Pressure
Fourier Analysis
Hemodynamics
Fast Fourier transforms
Healthy Volunteers

Keywords

  • Cardiac output variability
  • Coherence
  • LBNP
  • Regional cerebral O saturation

Cite this

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title = "New insight into the mechanism of cardiovascular dysfunction in the elderly: Transfer function analysis",
abstract = "This study sought to test the hypothesis that alterations in the relationships between (i) mean arterial pressure (MAP) and heart rate (HR), (ii) cardiac output (CO) and MAP, and (iii) total peripheral resistance (TPR) and MAP variability contribute to the diminished dynamic control of cardiovascular function with advanced age. Six-minute hemodynamic data were continuously recorded in 11 elderly (70 ± 2 years) and 11 young (26 ± 1 year) healthy volunteers under supine resting condition and during lower body negative pressure-induced orthostatic challenge. The data were converted using fast Fourier transform, and the ratio of cross-spectra to auto-spectra between two signals (i.e., MAP-HR, CO-MAP, TPR-MAP) was computed for transfer function analysis. In the low-frequency ranges (LF; 0.04-0.14 Hz) and high-frequency ranges (0.15-0.30 Hz), the gain and coherence of the transfer function describing the relationship between MAP-HR signals were significantly greater in younger than in older adults. The phase degree was significantly >0 in both groups under all conditions, suggesting that the MAP variability preceded the HR variability. In contrast, the coherence between CO-MAP signals in both age groups was <0.5, indicating that the beat-to-beat MAP variability was not significantly related to the CO signals. However, the transfer function gain and coherence of TPR-MAP signals were significantly greater in the young group (coherence ≥0.5 in the LF range), suggesting a more effective dynamic vasomotor control. In conclusion, the oscillations in CO-MAP signals are not significantly synchronized or not related in a simply linear fashion in both age groups. The MAP variability is more related to the oscillation of TPR signals in the young group only. Advanced age not only diminishes MAP-HR transfer function gain, but also weakens its coherence. Thus, alterations in the relationship between MAP-HR variability and TPR-MAP variability may significantly contribute to the diminished dynamic control of cardiovascular function manifest in the elderly.",
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New insight into the mechanism of cardiovascular dysfunction in the elderly : Transfer function analysis. / Guo, Hong; Schaller, Frederic; Tierney, Nancy; Smith, Scott A.; Shi, Xiangrong.

In: Experimental Biology and Medicine, Vol. 230, No. 8, 01.01.2005, p. 549-557.

Research output: Contribution to journalArticleResearchpeer-review

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AU - Schaller, Frederic

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AU - Smith, Scott A.

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