Associations and clinical relevance of aortic-brachial artery stiffness mismatch, aortic reservoir function, and central pressure augmentation

Central augmentation pressure (AP) and index (AIx) predict cardiovascular events and mortality, but underlying physiological mechanisms remain disputed. While traditionally believed to relate to wave reflections arising from proximal arterial impedance (and stiffness) mismatching, recent evidence suggests aortic reservoir function may be a more dominant contributor to AP and AIx. Our aim was therefore to determine relationships among aortic-brachial stiffness mismatching, AP, AIx, aortic reservoir function, and end-organ disease. Aortic (aPWV) and brachial (bPWV) pulse wave velocity were measured in 359 individuals (aged 61 ± 9, 49% male). Central AP, AIx, and aortic reservoir indexes were derived from radial tonometry. Participants were stratified by positive (bPWV > aPWV), negligible (bPWV ≈ aPWV), or negative stiffness mismatch (bPWV < aPWV). Left-ventricular mass index (LVMI) was measured by two-dimensional-echocardiography. Central AP and AIx were higher with negative stiffness mismatch vs. negligible or positive stiffness mismatch (11 ± 6 vs. 10 ± 6 vs. 8 ± 6 mmHg, P < 0.001 and 24 ± 10 vs. 24 ± 11 vs. 21 ± 13%, P = 0.042). Stiffness mismatch (bPWV-aPWV) was negatively associated with AP (r = -0.18, P = 0.001) but not AIx (r = -0.06, P = 0.27). Aortic reservoir pressure strongly correlated to AP (r = 0.81, P < 0.001) and AIx (r = 0.62, P < 0.001) independent of age, sex, heart rate, mean arterial pressure, and height (standardized β = 0.61 and 0.12, P ≤ 0.001). Aortic reservoir pressure independently predicted abnormal LVMI (β = 0.13, P = 0.024). Positive aortic-brachial stiffness mismatch does not result in higher AP or AIx. Aortic reservoir function, rather than discrete wave reflection from proximal arterial stiffness mismatching, provides a better model description of AP and AIx and also has clinical relevance as evidenced by an independent association of aortic reservoir pressure with LVMI.