Impaired vasoreactivity despite an increase in plasma nitrite in patients with abdominal aortic aneurysms

Abstract

Objective: This investigation was designed to determine whether differences in vasoreactivity occur in patients with abdominal aortic aneurysms (AAAs) as compared with patients with peripheral arterial occlusive disease (PAOD) or individuals (controls) without known vascular disease. Methods: Brachial artery vasoreactivity was assessed in a blinded fashion, after endothelium-dependent (ED) and endothelium-independent (EI) flow-mediated vasodilation, in age-matched, male patients with AAAs (n = 11) or PAOD (n = 9) or in controls (n = 10). There were no significant differences in prestudy systolic or diastolic blood pressure, body mass index, or antilipidemic medications among the groups studied. Exclusion criteria included diabetes and tobacco use within 3 months. Quantitative ultrasound scan measurements of brachial artery diameters were performed at rest and after either forearm ischemia (ED) or administration of 0.4 mg sublingual nitroglycerin (EI). Plasma nitric oxide (NOx = NO2 + NO3) was measured with the Saville assay. Asymmetric dimethylarginine, an endogenous inhibitor of NOx synthase, was measured with liquid chromatography. Results: Initial brachial artery diameters were not significantly different among the groups studied (4.85 ± 0.18 mm for AAA group, 4.82 ± 0.17 mm for PAOD group, 4.68 ± 0.20 mm for controls). ED and EI vasodilation was significantly less (P = .02 and .03, respectively) in the AAA group (-1.71 ± 1.52 and 8.33 ± 1.13, respectively) when compared with the controls (2.96 ± 1.04 and 13.88 ± 2.16, respectively). However, plasma NOx was significantly increased (P = .01) in the AAA group (7.86 ± 0.85 μmol/L) as compared with both controls (5.13 ± 0.63 μmol/L) and PAOD (4.85 ± 0.46 μmol/L). Asymmetric dimethylarginine levels were decreased in the AAA group (0.34 ± 0.05 μmol/L) as compared with the PAOD group (0.46 ± 0.09 umol/L). No correlation existed between aneurysm size and ED or EI vasodilation or plasma NOx. Conclusion: This study is the first to document a divergence between ED and EI vasoreactivity and systemic NO metabolites in patients with AAAs. It is speculated that a dysfunctional vessel wall response, rather than a lack of NO, may be important in the pathogenesis of AAAs. Copyright © 2002 by The Society for Vascular Surgery and The American Association for Vascular Surgery.