Warfarin treatment quality and outcomes in patients with non-valvular atrial fibrillation and CKD G3-G5D

Introduction: Warfarin treatment quality is calculated as time in therapeutic range (TTR). TTR ≥ 70 % is considered reducing the risk of adverse events for patients with atrial fibrillation (AF). The association of TTR and adverse events in chronic kidney disease (CKD) is however poorly investigated. The aim is to explore this further. Materials and methods: Swedish cohort study based on national healthcare registers between 2009 and 2018, including Swedish Renal Registry, Swedish Stroke Register and AuriculA - the Swedish national quality register for AF and anticoagulation. Investigating the effect of individual TTR (iTTR) and iTTR ≥ 70 % versus <70 % on the risk of ischemic stroke, major bleeding and death for patients with CKD GFR category 3–5 (G3-G5) including patients on dialysis (G5D) and non-valvular AF (NVAF). Results: Of 2379 included patients 21.9 % had G3, 47.5 % G4, 10.8 % G5 and 19.8 % G5D. TTR in G3 was 75.6 %, G4 72.2 %, G5 67.6 % and G5D 62.0 %. Increase by 10 percentage points iTTR conferred lower risk of major bleeding, ischemic stroke and death for all patients (hazard ratio 0.91 (95 % Confidence interval 0.87–0.94), 0.92 (0.85–0.99) and 0.88 (0.85–0.90)). iTTR≥ 70 % versus <70 % was associated with lower risk of bleeding and death in all patients (0.63 (0.51–0.77) and (0.51 (0.43–0.61)), and a non-significant tendency towards lower stroke risk (0.67 (0.43–1.06)). Conclusions: Warfarin treatment quality worsens with decreasing GFR. Higher iTTR confers lower risk of bleeding, ischemic stroke and death in patients with NVAF and G3-G5D. iTTR ≥ 70 % was associated with better safety profile. Close monitoring of patients with CKD on warfarin is recommended