Abstract and Introduction
Abstract
Aims Limited data are available on the impact of renal function on the outcome of patients with atrial fibrillation (AF).
Methods and results AMADEUS was a multicentre, randomized, open-label non-inferiority study that compared fixed-dose idraparinux with conventional anticoagulation by dose-adjusted vitamin K antagonists. We performed a post hoc analysis to assess the impact of renal function on the outcomes of anticoagulated AF patients. The primary efficacy outcome was the composite of stroke/systemic embolism (SE). The principal safety outcome of this analysis was major bleeding. We calculated c-indexes, reflecting the ability for discriminating diseased vs. non-diseased patients, and the net reclassification improvement (NRI, an index of inferior/superior performance of risk estimation scores). Of 4576 patients, 45 strokes and 103 major bleeding events occurred following an average follow-up of 325 ± 164 days. Patients with CrCl >90 mL/min had an annual stroke/SE rate of 0.6% compared with 0.8% for those with CrCl 60–90 mL/min and 2.2% for those with CrCl <60 mL/min (P < 0.001 for linear association). After adjusting for stroke risk factors, patients with CrCl <60 mL/min had more than two-fold higher risk of stroke/SE and almost 60% higher risk of major bleeding compared with those with CrCl ≥60. In patients with the CHA2DS2VASc score 1–2, CrCl <60 mL/min was associated with eight-fold higher stroke risk. When added to the CHA2DS2VASc or CHADS2 scores, CrCl <60 mL/min did not improve the c-indexes for CHADS2 (P = 0.054) or CHA2DS2VASc (P = 0.63) but resulted in significant NRI (0.26, P = 0.02) in this anticoagulated trial cohort.
Conclusion Renal impairment (CrCl <60 mL/min) doubles the risk of stroke and increased the risk of major bleeding by almost 60% in anticoagulated patients with AF. Renal impairment was additive to stroke risk prediction scores based on a significant NRI, but no significant improvement in discrimination ability (based on c-indexes) for CHA2DS2VASc or CHADS2 was observed.
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Introduction
The prevalence of atrial fibrillation (AF) in end-stage chronic kidney disease (CKD) is high reaching 27% in patients on long-term haemodialysis. Even less advanced stages of CKD are associated with high prevalence of AF. Moreover, CKD is a common comorbidity among AF patients.
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Chronic kidney disease results in complex pathophysiological changes, involving both hypo- and hypercoagulability. An intimate relationship between CKD and oral anticoagulant (OAC)-related haemorrhagic events is well established. As a result, severe CKD is a predictor in most OAC-related bleeding risk estimation tools. On the other hand, patients with AF and advanced CKD have higher risk of thromboembolic events compared with AF patients with normal renal function.
Current AF stroke risk stratification scores do not include CKD as a potential risk factor for thromboembolic events. Moreover, there is limited information on the impact of mild or moderate CKD on the outcome(s) of anticoagulated patients with AF, and whether moderate-severe CKD improves the predictive value of stroke risk stratification.
The objective of this study was to evaluate the impact of renal function on the outcome of anticoagulated AF patients and second, to assess the additive prognostic value of moderate-severe CKD on the two widely used stroke risk prediction scores, the CHA2DS2VASc and CHADS2 scores.