%0 Journal Article
%T The Age-Dependent Contribution of Aortic Incident and Reflected Pressure Waves to Central Blood Pressure in African-Americans
%A Haroon Kamran
%A Jason M. Lazar
%A Rinkesh Patel
%A IIir Maraj
%A Heather Berman
%A Louis Salciccioli
%J International Journal of Hypertension
%D 2011
%I Hindawi Publishing Corporation
%R 10.4061/2011/585703
%X Aging is associated with increased central aortic systolic pressure (CSP) and pulse pressure which are predictive of cardiovascular events. Mechanisms implicated for higher central pressures include a higher forward incident pressure wave (P1), higher augmented pressure (AP), and shorter reflected wave round trip travel time (Tr). African-Americans (AA) have more frequent and deleterious blood pressure elevation. Using applanation tonometry, we studied the association of age and CSP with P1 and AP in 900 AA subjects. Data showed that in subjects ¡Ü50 years old, CSP was mediated by AP but not P1 or Tr, whereas in those >50, CSP was mediated by both AP and P1 and to a lesser extent by Tr. Predictive models were significant ( ) for both age groups. In conclusion, wave reflection is the primary determinant of CSP in younger AA, while in older subjects, CSP is mediated by both the magnitude and timing of wave reflection as well as aortic impedance. 1. Introduction Vascular aging and remodeling predominantly affects the large elastic arteries, with the unfavorable consequence of increased aortic stiffness and higher central systolic (CSP) and pulse pressure (PP) [1]. In recent years, it has been demonstrated that central pressures are more closely related to cardiovascular outcomes as compared to peripheral pressures [2]. Pathological changes within the arterial system lead to hemodynamic alterations that are reflected in the aortic waveform. The growing use of applanation tonometry has rejuvenated interest in the mechanisms of blood pressure elevation. Several mechanisms have been proposed for the higher central pressures observed with aging. There may be an increased forward incident pressure wave (P1), a higher augmented pressure (AP) and augmentation index (AI), and a shorter round trip travel time of the reflected wave (Tr) [3]. Aortic characteristic impedance also increases with age, thereby increasing P1. Greater AP due to increased wave reflection is the conventional explanation of why CSP increases with age, with age-related increases in aortic stiffness shortening Tr and causing the reflected wave to sum on the incident wave during systole [4¨C8]. Other investigators have found P1 to be the more important determinant of central pressure [9, 10]. A recent study in a large cohort of normal subjects found the contribution of AP and P1 to the CSP to vary between those younger and older than 60 years [11]. Thus, the reasons for higher CSP and PP with advancing age have not been fully clarified. African-Americans (AA) have a high prevalence of hypertension,
%U http://www.hindawi.com/journals/ijhy/2011/585703/