Renal impairment and ischaemic stroke risk assessment in patients with atrial fibrillation: The Loire Valley Atrial Fibrillation Project

OBJECTIVE: To determine the risk of ischaemic stroke/ thromboembolism associated with renal impairment and its incremental predictive value over established risk stratification scores (CHADS2 and CHA2DS2-VASc) in patients with AF. BACKGROUND: Risk stratification schemes for prediction of ischaemic stroke(IS)/thromboembolism (TE) in patients with atrial fibrillation (AF) are validated but do not include renal impairment. METHODS: Patients diagnosed with non-valvular AF and available estimated glomerular filtration rate (eGFR) data in a four-hospital institution between 2000 and 2010 were identified. The study population was stratified by renal impairment defined by serum creatinine level and by eGFR measured at time of diagnosis of AF. Independent risk factors of IS/TE (including renal impairment) were investigated in Cox regression models. The incremental predictive value of renal impairment over CHADS2 and CHA2DS2-VASc were assessed using the c-statistic, net reclassification improvement (NRI) and integrated discrimination improvement (IDI). We focused on the 1-year outcomes in our analyses. RESULTS: Of 8962 eligible individuals, 5912(66.0%) had NVAF and available eGFR data. Renal impairment by both creatinine and eGFR definitions was associated with higher rates of IS/TE at 1 year, compared to normal renal function. After adjustment for CHADS2 risk factors, renal impairment did not significantly increase the risk of IS/TE at 1 year (HR 1.06(95%CI 0.75-1.49) for renal impairment and 1.09 (0.84-1.41) for eGFR respectively). When renal impairment was added to existing risk scoring systems for stroke/TE (CHADS2 and CHA2DS2VASc), it did not independently add to the predictive value of the scores, whether defined by serum creatinine level or eGFR. This was evident even when the analysis was confined to only those patients with at least 1 year of follow-up. CONCLUSION: Renal impairment was not an independent predictor of IS/TE in patients with AF and did not significantly improve the predictive ability of the CHADS2 or CHA2DS2VASc scores.