Background: There is a high prevalence of atrial fibrillation (AF) in patients undergoing haemodialysis. Oral anticoagulant therapy with vitamin K antagonists (VKAs) is the only accepted treatment for the prevention of thromboembolism in haemodialysis patients with AF. However, in this population, the risk of bleeding is greatly increased. The aim of the study was to evaluate the ability of treatment quality indicators of VKA therapy to predict mortality and bleedings in a population of haemodialysis patients with AF.
Materials and methods: A total of 129 patients were included in this cohort study. Deaths and bleeding events were recorded during a follow-up of 4 years. In all patients, International Normalized Ratio (INR) values were assessed at least once a month. Time in therapeutic range (TTR) and INR variability, as measured by the standard deviation of INR, were updated at each INR measurement. A Cox model with time-dependent co-variates and sandwich variance was applied.
Results: During follow-up, 71 patients died and 55 bleeding episodes occurred in 31 patients. INR variability was the only indicator associated with both mortality (hazard ratio [HR]=1.67, 95% confidence interval [CI] 1.12; 2.49, p=0.012) and bleeding (HR=2.85, 95% CI: 1.71; 4.75, p=0.0001). HR of mortality was higher in patients with INR >3 (HR=2.06, 95% CI: 1.09; 3.88, p=0.0259) than in subjects in therapeutic range 2<INR≤3. TTR was inversely associated with the risk of recurrent haemorrhagic events (HR=0.88, 95% CI: 0.80; 0.95, p=0.0023), but not with a first episode of bleeding. Results were consistent after censoring patients at VKA withdrawal.
Discussion: Our study suggests that, in haemodialysis patients with AF taking VKAs, INR variability is the quality indicator that best predicts clinical outcomes. In this population, if more treatment quality indicators are considered together, it may become easier to identify patients at particularly high risk of bleeding and death.