MARKED INCREASES IN PROXIMAL AORTIC CHARACTERISTIC IMPEDANCE AND HENCE FORWARD WAVE PRESSURES BEYOND BRACHIAL BLOOD PRESSURE IN ANGIOGRAPHIC PROVEN CORONARY ARTERY DISEASE

Abstract

Objective: Although indexes of aortic stiffness increase the risk for coronary artery disease (CAD), the extent to which proximal aortic stiffness increases enhance central arterial forward wave pressures beyond changes in peripheral pressures, is uncertain. We aimed to determine whether increases in proximal aortic stiffness, as indexed by aortic characteristic impedance (Zc) translate into an enhanced central arterial pressure for a given brachial BP. Design and method: From central pressure, aortic velocity and outflow tract diameter measurements and echocardiography, we determined Zc and arterial pressure wave morphology in 71 patients with angiographic proven CAD and all other cardiac pathology excluded. We compared central arterial function in these patients with 230 age and sex-matched controls from a community study, and in patients with stroke and CLI (n = 287) diagnosed in a hospital setting. Results: Adjusting for confounders, including mean arterial pressure, and aortic root diameter, as compared to controls, both Zc and the pressures generated by the product of peak aortic flow (Q) and Zc (PQxZc) were markedly increased in patients with CAD (p<0.0001) and those with stroke or CLI (p<0.005). Moreover, compared to patients with stroke and CLI, those with CAD also had marked increases in both Zc and PQxZc (p<0.0001). Consequently, with adjustments for the same confounders, pressures generated by forward wave pressures (Pf) were markedly increased in patients with CAD as compared to controls and to patients with alternative arterial diseases (p<0.0001). Importantly, after further adjustments for brachial PP or SBP, the higher Pf values in patients with CAD were retained (p<0.005 to <0.0001). However, with adjustments for brachial SBP and confounders, central aortic PP did not differ between groups. Conclusions: Independent of confounders and aortic root diameter, a marked increase in proximal aortic Zc occurs in patients with CAD as compared to both controls and patients with arterial disease in alternative beds. This translates into a greater central arterial pulsatile load determined by forward travelling pressure waves, but not peak central PP than that predicted by brachial BP measurements. These data support a need for intense brachial BP lowering in CAD.