A prospective study of estimated glomerular filtration rate and outcomes in patients with atrial fibrillation: The Loire Valley Atrial Fibrillation Project

Purpose: Patients with chronic kidney disease (CKD) are more likely to develop atrial fibrillation (AF) than individuals with normal renal function, and are more likely to suffer stroke/thromboembolism (TE). Only one study has considered the association between estimated glomerular filtration rate (eGFR) and stroke/TE, and none have considered impact of eGFR on bleeding. We therefore conducted the first long-term prospective study of eGFR and stroke/TE, mortality and bleeding in an AF population, unrestricted by age or comorbidity. Methods: Patients diagnosed with non-valvular AF (NVAF) and available eGFR data in a four-hospital institution between 2000 and 2010 were identified. The study population was stratified into five categories according to eGFR (in ml/min/1.73 m2): ≥90, 60-89, 30-59, 15-29, and <15, analysing risk factors, as well as incidence and survival for all-cause mortality, bleeding and stroke/TE. Results: Of 8962 eligible individuals, 5912 (66.0%) had NVAF and available eGFR data. In non-anticoagulated and anticoagulated individuals, rates of stroke/TE were 7.4 (95% CI 6.3-8.6) and 7.2 (6.3-8.2) per 1000 person years, respectively. Incidence rates of all-cause mortality were 13.4 (12.0-15.0) and 9.4 (8.3-10.5), respectively, and of major bleeding were 6.2 (5.2-7.3) and 9.0 (8.0-10.1) per 1000 person years, respectively. Rates of all events increased with decreasing eGFR, regardless of OAC, and rates of stroke/TE were lower in individuals receiving OAC. When the benefit of ischaemic stroke reduction is balanced against the increased risk of haemorrhagic stroke amongst patients with renal impairment, the net clinical benefit (NCB) was clearly positive in favour of OAC use: for individuals with a eGFR=30-59, NCB=2.06 (95% CI 1.40-2.88), whilst for eGFR<30, NCB=6.69 (3.27-12.78). At 1 year, in individuals with eGFR>60mL/min/1.73m2 and with eGFR <30 mL/min/1.73m2, overall rates of stroke/TE were 3.3% and 7.0%, respectively. Overall rates of all-cause mortality were 4.2% and 17.6%, and of bleeding were 3.8% and 10.0%, respectively. Conclusions: Renal impairment is a poor prognostic indicator of stroke/TE, bleeding and mortality in the long-term in individuals with NVAF across the whole range of renal function. OAC use was associated with a lower incidence of stroke/TE and mortality at 1 year, compared with non-anticoagulated individuals in all categories of renal function as measured by eGFR. The NCB balancing ischaemic stroke against serious bleeding was positive, in favour of OAC use amongst patients with renal impairment.