Determination of age-related increases in large artery stiffness by digital pulse contour analysis

The stiffness of the aorta can be determined by measuring carotid–femoral pulse wave velocity (PWV_cf). PWV may also influence the contour of the peripheral pulse, suggesting that contour analysis might be used to assess large artery stiffness. An index of large artery stiffness (SI_DVP) derived from the digital volume pulse (DVP) measured by transmission of IR light (photoplethysmography) was examined. SI_DVP was obtained from subject height and from the time delay between direct and reflected waves in the DVP. The timing of these components of the DVP is determined by PWV in the aorta and large arteries. SI_DVP was, therefore, expected to provide a measure of stiffness similar to PWV. SI_DVP was compared with PWV_cf obtained by applanation tonometry in 87 asymptomatic subjects (21–68 years; 29 women). The reproducibility of SI_DVP and PWV_cf and the response of SI_DVP to glyceryl trinitrate were assessed in subsets of subjects. The mean within-subject coefficient of variation of SI_DVP, for measurements at weekly intervals, was 9.6%. SI_DVP was correlated with PWV_cf (r = 0.65, P<0.0001). SI_DVP and PWV_cf were each independently correlated with age and mean arterial blood pressure (MAP) with similar regression coefficients: SI_DVP = 0.63+0.086×age+0.042×MAP (r = 0.69, P<0.0001); PWV_cf = 0.76+0.080×age+0.053×MAP (r = 0.71, P<0.0001). Administration of glyceryl trinitrate (3, 30 and 300 μg/min intravenous; each dose for 15 min) in nine healthy men produced similar changes in SI_DVP and PWV_cf. Thus contour analysis of the DVP provides a simple, reproducible, non-invasive measure of large artery stiffness.