Vitamin K antagonist use and mortality in dialysis patients

Background. The risk-benefit ratio of vitamin K antagonists for different CHA(2)DS(2)-VASc scores in patients with end-stage renal disease treated with dialysis is unknown. The aim of this study was to investigate the association between vitamin K antagonist use and mortality for different CHA(2)DS(2)-VASc scores in a cohort of end-stage renal disease patients receiving dialysis treatment. Methods. We prospectively followed 1718 incident dialysis patients. Hazard ratios were calculated for all-cause and cause-specific (stroke, bleeding, cardiovascular and other) mortality associated with vitamin K antagonist use. Results. Vitamin K antagonist use as compared with no vitamin K antagonist use was associated with a 1.2-fold [95% confidence interval (95% CI) 1.0-1.5] increased all-cause mortality risk, a 1.5-fold (95% CI 0.6-4.0) increased stroke mortality risk, a 1.3-fold (95% CI 0.4-4.2) increased bleeding mortality risk, a 1.2-fold (95% CI 0.9-1.8) increased cardiovascular mortality risk and a 1.2-fold (95% CI 0.8-1.6) increased other mortality risk after adjustment. Within patients with a CHA(2)DS(2)-VASc score <= 1, vitamin K antagonist use was associated with a 2.8-fold (95% CI 1.0-7.8) increased all-cause mortality risk as compared with no vitamin K antagonist use, while vitamin K antagonist use within patients with a CHA(2)DS(2)-VASc score >= 2 was not associated with an increased mortality risk after adjustment. Conclusion. Vitamin K antagonist use was not associated with a protective effect on mortality in the different CHA(2)DS(2)-VASc scores in dialysis patients. The lack of knowledge on the indication for vitamin K antagonist use could lead to confounding by indication.