Relations of aortic stiffness with arterial damage beyond brachial pressure are both dependent and independent of central arterial pulsatile load

Aim:We aimed to determine whether the impact of aortic stiffness on atherosclerotic or small vessel end organ damage beyond brachial blood pressure depends in-part on stiffness-induced increases in central arterial pressures produced by an enhanced resistance to flow (characteristic impedance, Zc).Methods:We studied 1021 participants, 287 with stroke or critical limb ischaemia, and 734 from a community sample with atherosclerotic or small vessel end organ measures. Central arterial haemodynamics were determined from arterial pressure (SphygmoCor) and velocity and diameter assessments in the outflow tract (echocardiography).Results:Although Zc and carotid-femoral pulse wave velocity (PWV) were correlated (P < 0.0001), these relations were not independent of confounders (P = 0.90). Both Zc and hence central arterial pressures generated by the product of Zc and aortic flow (Q) (PQxZc), as well as PWV were independently associated with carotid intima-media thickness, estimated glomerular filtration rate (eGFR), endothelial activation markers [vascular cell adhesion molecule-1 (V-CAM-1)] and events. With further adjustments for brachial pulse pressure (PP) or SBP, PWV and PQxZcwere both associated with eGFR and V-CAM-1. Relationships between PWV and eGFR or V-CAM-1 were independent of PQxZc(P < 0.05) and relationships between PQxZcand eGFR and V-CAM-1 were independent of PWV (P < 0.005). Similarly, with adjustments for confounders and brachial PP or SBP, across the full adult lifespan, both aortic PWV and PQxZcwere increased in those with arterial events (P < 0.005). Relationships between PWV and events were again independent of PQxZc(P < 0.005) and between PQxZcand events were independent of PWV (P < 0.0001).Conclusion:Beyond brachial blood pressure, the impact of aortic stiffness on arterial damage involves effects that are both dependent (proximal aortic Zc and hence PQxZc) and independent (full aortic length indexed by PWV) of central arterial pulsatile load. Hence, PWV and brachial PP may be insufficient to account for all of the damage mediated by increases in aortic stiffness.