Contribution of backward and forward wave pressures to age-related increases in aortic pressure in a community sample not receiving antihypertensive therapy

Abstract

Reports on the contribution of aortic forward (Pf) and backward (Pb) wave pressures to age-related increases in central aortic pulse pressure (PPc) have been confounded by the use of participants receiving antihypertensive therapy. We assessed the relative contribution of Pf and Pb to age-related increases in PPc (radial applanation tonometry and SphygmoCor software using an assumed triangular wave for wave separation analysis) in 892 community participants not receiving antihypertensive therapy. We validated our results using aortic flow waves (echocardiography) for wave separation analysis in 254 of these participants. In multivariate regression models in those aged <50 years, adjustments for both Pb and a Pf-independent measure of reflected wave function (RM = Pb/Pf), but not Pf abolished the impact of age on PPc. However, in those aged >50 years, adjustments for Pf (β-coefficient: 0.25 ± 0.06 vs. 0.74 ± 0.08; P < .0001) and Pb (0.04 ± 0.04 vs. 0.74 ± 0.08; P < .0001), but not RM markedly decreased the relationship between age and PPc. On product of coefficient mediation analysis, whether assessed in men or in women, in those participants aged <50 years, independent of several confounders and mean arterial pressure, Pb (P < .005), but not Pf contributed to age-related increases in PPc. In contrast, in those participants aged ≥50 years, independent of several confounders and mean arterial pressure, Pb (P < .005) and Pf (P < .01) contributed to age-related increases in PPc, and Pb effects were markedly diminished by adjustments for Pf (0.26 ± 0.002 vs. 0.52 ± 0.003 mm Hg per year, P < .0001 for comparison). In conclusion, independent of the effects of antihypertensive therapy, aortic backward waves contribute to age-related increases in aortic PPc across the adult lifespan, but at an older age, this effect may be attributed in part to the impact of forward on backward wave pressures.