Time in therapeutic range and outcomes after warfarin initiation in newly diagnosed atrial fibrillation patients with renal dysfunction

Background-it is unknown whether renal dysfunction conveys poor anticoagulation control in warfarin-treated patients with atrial fibrillation and whether poor anticoagulation control associates with the risk of adverse outcomes in these patients. methods and results-this was an observational study from the stockholm creatinine measurements (scream) cohort including all newly diagnosed atrial fibrillation patients initiating treatment with warfarin (n=7738) in stockholm,sweden,between 2006 and 2011. estimated glomerular filtration rate (egfr; ml/min per 1.73 m2) was calculated from serum creatinine. time-in-therapeutic range (ttr) was assessed from international normalized ratio (inr) measurements up to warfarin cessation,adverse event,or end of follow-up (2 years). adverse events considered a composite of intracranial hemorrhage,ischemic stroke,myocardial infarction,or death. during median 254 days,ttr was 83%,based on median 21 inr measurements per patient. ttr was 70% among patients with egfr < 30,around 10% lower than in those with normal renal function. during observation,adverse events occurred in 4.0% of patients,and those with ttr ≤75% were at higher adverse event risk. this was independent of patient characteristics,comorbidities,number of inr tests,days exposed to warfarin,and,notably,independent of egfr: adjusted odds ratio (or) 1.84 (95% ci,1.41-2.40) for ttr 75% to 60% and adjusted or 2.09 (1.59-2.74) for ttr < 60%. no interaction was observed between egfr and ttr in association to adverse events (p=0.2). conclusion-severe chronic kidney disease (egfr < 30) patients with atrial fibrillation have worse inr control while on warfarin. an optimal ttr (>75%) is associated with lower risk of adverse events,independently of underlying renal function. © 2017 the authors.