title: Asymmetric Dimethylarginine Levels are Highly Associated With Atrial Fibrillation in an Elderly Population.
abstract: BACKGROUND
  The importance of endothelial dysfunction in atrial fibrillation (AF) is not clarified. The aim of this study was to evaluate endothelial dysfunction assessed by selected inflammatory and haemostatic endothelial markers and nitric oxide (NO) associated variables as related to the presence of AF in an elderly population. NO is known to express anti-thrombotic as well as vasoactive properties.
  
  
  METHODS
  This is a cross sectional study of 75-year old subjects with AF (n = 62) and control subjects in sinus rhythm (n = 124), matched for gender. Fasting blood samples were collected for analyses of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NO-synthase, L-arginine, E-selectin, vascular cell adhesion molecule-1 (VCAM-1) and von Willebrand factor (vWF).
  
  
  RESULTS
  Levels of vWF and ADMA were significantly higher in AF patients vs controls (P = 0.023 and P < 0.001, respectively) and the L-arginine/ADMA ratios were lower (P = 0.015), the latters still significant after adjustment for relevant covariates (P = 0.007 and P = 0.037, respectively). No significant differences in the levels of VCAM-1 and E-selectin were observed between the groups. When dividing the ADMA levels into quartiles there was a significant trend for having AF with increasing levels of ADMA (P < 0.001) with a cut-off at the 25th percentile (< 0.54 µmol/L), giving an adjusted OR for having AF of 12.46 (95% CI 3.11 - 49.86) (P < 0.001) with higher levels. A similar inverse trend was seen for the L-arginine/ADMA ratio.
  
  
  CONCLUSIONS
  Our population of 75-year-old AF patients had significantly impaired endothelial function assessed by increased levels of vWF, and more pronounced by high levels of ADMA. The results indicate AF in the elderly to be closely associated with the regulatory pathway of NO.
authors.affiliation: Center for Clinical Heart Research, Oslo University Hospital Ulleval, Norway; Department of Cardiology, Oslo University Hospital Ulleval, Norway; Faculty of Medicine, University of Oslo, Norway.
authors.forename: Ingebjorg
authors.initials: I
authors.lastname: Seljeflot
authors.affiliation: Medical Research Department, Department of Medicine, Vestre Viken Hospital Trust, Rud, Norway.
authors.forename: Sara
authors.initials: S
authors.lastname: R Ulimoen
authors.affiliation: Medical Research Department, Department of Medicine, Vestre Viken Hospital Trust, Rud, Norway.
authors.forename: Steve
authors.initials: S
authors.lastname: Enger
authors.affiliation: Center for Clinical Heart Research, Oslo University Hospital Ulleval, Norway.
authors.forename: Vibeke
authors.initials: V
authors.lastname: Bratseth
authors.affiliation: Center for Clinical Heart Research, Oslo University Hospital Ulleval, Norway; Department of Cardiology, Oslo University Hospital Ulleval, Norway; Faculty of Medicine, University of Oslo, Norway.
authors.forename: Harald
authors.initials: H
authors.lastname: Arnesen
authors.affiliation: Medical Research Department, Department of Medicine, Vestre Viken Hospital Trust, Rud, Norway.
authors.forename: Arnljot
authors.initials: A
authors.lastname: Tveit
keywords: ADMA; Atrial fibrillation; Elderly; Endothelial cell adhesion molecules; Endothelial dysfunction; Von Willebrand factor