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CLINICAL STUDY: ARTERIAL DISTENSIBILITY

Inter-relations among declines in arterial distensibility, baroreflex function and respiratory sinus arrhythmia

^* Laboratories for Cardiovascular Research, Hebrew Rehabilitation Center For Aged Research and Training Institute, and Harvard Medical School Division on Aging, Boston, MassachusettsUSA

Manuscript received May 31, 2001; revised manuscript received January 28, 2002, accepted February 6, 2002.

^* Reprint requests and correspondence: J. Andrew Taylor, PhD, Director, Laboratories for Cardiovascular Research, HRCA Research and Training Institute, 1200 Centre Street, Boston, Massachusetts, USA 02131.
ataylor{at}mail.hrca.harvard.edu

OBJECTIVES: We hypothesized that structural and neural cardiovascular (CV) deficits may be intimately linked. Specifically, decreased carotid distensibility with age may blunt the arterial baroreflex, thereby reducing resting cardiac vagal tone.

BACKGROUND: Increased CV risk is associated with lower carotid distensibility, impaired baroreflex function and reduced respiratory sinus arrhythmia (RSA), possibly representing a direct path between structural and neural CV deficits.

METHODS: We estimated the mechanostructural and neural components of baroreflex function and examined their relation to RSA in young (20 to 31 years) and older (59 to 71 years) subjects rigorously screened for CV and autonomic diseases.

RESULTS: In the older subjects, RSA was < 20% of that in the younger subjects. Moreover, mechanical transduction of pressure into barosensory vessel stretch was 40% lower (p < 0.05) and arterial baroreflex gain more than 60% lower (p < 0.05) in the older group. Although neural transduction of stretch into vagal outflow only tended to be less (p < 0.08), it was an important determinant of baroreflex function. A path analysis model showed comparable contributions of both the mechanical and neural components to baroreflex gain; however, lower overall baroreflex gain in the older group did not relate to lower RSA.

CONCLUSIONS: These data suggest that decreased carotid distensibility does reduce baroreflex function with age, but this does not lead to reduced resting vagal outflow.

Abbreviations and Acronyms   CV   cardiovascular   ECG   electrocardiogram   RSA   respiratory sinus arrhythmia

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