G. J. Zahner1, K. A. Spaulding1,2, M. S. Schaller1, S. C. Walker1, N. K. Hills3, W. J. Gasper1,2, M. Grenon1,2 1University Of California – San Francisco,Department Of Surgery,San Francisco, CA, USA 2San Francisco VA Medical Center,Vascular Surgery Section,San Francisco, CA, USA 3University Of California – San Francisco,Department Of Epidemiology And Biostatistics,San Francisco, CA, USA
Introduction:
Arterial stiffness, measured by the augmentation index (AIX) from radial artery tonometry, and endothelial dysfunction, measured by brachial-artery flow-mediated vasodilation (FMD), have each been associated with increased risk of cardiovascular events. The relationship of these parameters to one another in patients with peripheral artery disease (PAD) is less well understood.
Methods:
In a cross-section of 123 vascular surgery outpatients, the current study examined the association between FMD and AIX in patients with PAD and in patients with atherosclerotic risk factors. PAD was defined as symptoms of claudication with an ankle-brachial index (ABI) of <.9 or a history of revascularization for symptomatic PAD, while controls had no history of atherosclerotic vascular disease and an ABI≥.9 but presented with traditional risk factors for PAD.
Results:
Compared to controls (n=32), patients with PAD (n=91) had lower FMD (6.3 ± 3.8 vs. 8.4 ± 3.7, p=.008), while central augmentation index normalized to 75bpm (central AIX) (25.5 ± 9.0 vs. 19.3 ± 8.6, p=.001) and peripheral augmentation index (peripheral AIX) (91.3 ± 14.5 vs. 81.3 ± 11.4, p=.001) were higher. FMD was not significantly correlated with either central or peripheral AIX (central: r=-.05; 95% CI -.23, .13; p=.58; peripheral: r=.01; 95% CI -.17, .19; p=.89) across the entire cohort or in either the patients with PAD (central AIX: r=.07, 95% CI -.13-.28, p=.48; peripheral AIX: r=.13, 95% CI -.08, .33, p=.23) or controls (central AIX: r=-.14, 95% CI -.47,.22, p=.43; peripheral AIX: r=-.02, 95% CI -.36, .33, p=.92). When AIX and FMD were combined in a single model, higher AIX remained independently associated with PAD.
Conclusion:
In an analysis of vascular surgery outpatients, no correlation between FMD and AIX was detected, despite adequate power to detect a clinically meaningful relationship. Larger prospective studies are needed to determine whether the inclusion of both parameters improves predictive models for the early identification and potential risk stratification of PAD patients.