Published Online
on May 2, 2005

A more recent version of this article appeared on June 1, 2005

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Submitted on November 23, 2004
Revised on December 15, 2004

Aortic Input Impedance Increases With Age in Healthy Men and Women

Luciano Mazzaro; Stephen J. Almasi; Robin Shandas; Douglas R. Seals; and Phillip E. Gates^*

From the Departments of Integrative Physiology (L.M., D.R.S., S.J.A., P.E.G.) and Mechanical Engineering (L.M., R.S.), University of Colorado, Boulder, Colo; the Department of Medicine, Division of Geriatric Medicine (D.R.S.), University of Colorado Health Sciences Center, Denver, Colo; and the Division of Cardiology (R.S.), The Children’s Hospital, Denver, Colo.

^* To whom correspondence should be addressed. E-mail: phillip.gates{at}colorado.edu.

Abstract--Aortic input impedance represents the hydraulic load presented by the systemic circulation to the left ventricle of the heart and is increased in patients with cardiovascular disease. Aging is a strong independent risk factor for cardiovascular disease and could exert this effect partly through an increase in modulus of aortic input impedance. We used a novel noninvasive technique to determine aortic input impedance in 71 healthy men and women aged 20 to 69 years. We found that the aortic input impedance spectrum was shifted rightward with advancing age, characterized by a 37% increase in the frequency of the minimum modulus between the third and seventh decade (P<0.0001). The frequency of the minimum modulus correlated with age in all subjects (r=0.48; P<0.0001), in men (r=0.43; P<0.005), and in women (r=0.53; P=0.001). Although several physical characteristics were associated with the frequency of the minimum modulus (bivariate correlation), a regression model that included age and these physical characteristics showed that age was the only independent predictor of the frequency of the minimum modulus. We conclude that aortic input impedance increases with advancing age in healthy men and women. This increase in aortic input impedance may be an important mechanism by which age increases the risk of cardiovascular disease in humans.

Key words: aorta • applanation tonometry • Doppler echocardiography • hemodynamics • ventricular-vascular coupling

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