Arterial pressure waves were recorded noninvasively from the carotid, radial, femoral, or all three of these arteries of 1,005 normal subjects, aged 2-91 years, using a new transcutaneous tonometer containing a high fidelity Millar micromanometer. Waves were ensemble-averaged into age-decade groups. Characteristic changes were noted with increasing age. In all sites, pulse amplitude increased with advancing age (carotid, 91.3%; radial 67.5%; femoral, 50.1% from first to eighth decade), diastolic decay steepened, and diastolic waves became less prominent. In the carotid pulse, there was, in youth, a second peak on the downstroke of the waves in late systole. After the third decade, this second peak rose with age to merge with and dominate the initial rise. In the radial pulse, a late systolic wave was also apparent, but this occurred later; with age, this second peak rose but not above the initial rise in early systole, even at the eighth decade. In the femoral artery, there was a single systolic wave at all ages. Aging changes in the arterial pulse are explicable on the basis of both an increase in arterial stiffness with increased pulse-wave velocity and progressively earlier wave reflection. These two factors may be separated and effects of the latter measured from pressure wave-contour analysis using an "augmentation index," determined by a computer algorithm developed from invasive pressure and flow data. Changes in peak pressure in the central (carotid) artery show increasing cardiac afterload with increasing age in a normal population; this can account for the cardiac hypertrophy that occurs with advancing age (even as other organs atrophy) and the predisposition to cardiac failure in the elderly. Identification of mechanisms responsible offers a new approach to reduction of left ventricular afterload.
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