Association between impaired renal function and stroke outcome in patients with versus without atrial fibrillation

Both atrial fibrillation and chronic kidney disease increase the risk of stroke and systemic thromboembolism. However, these risks, and the effects of antithrombotic treatment, have not been thoroughly investigated in patients with both conditions. Using Danish national registries, we identified all patients discharged from the hospital with a diagnosis of nonvalvular atrial fibrillation between 1997 and 2008. The risk of stroke or systemic thromboembolism and bleeding associated with non-end-stage chronic kidney disease and with end-stage chronic kidney disease (i.e., disease requiring renal-replacement therapy) was estimated with the use of time-dependent Cox regression analyses. In addition, the effects of treatment with warfarin, aspirin, or both in patients with chronic kidney disease were compared with the effects in patients with no renal disease. Of 132,372 patients included in the analysis, 3587 (2.7%) had non-end-stage chronic kidney disease and 901 (0.7%) required renal-replacement therapy at the time of inclusion. As compared with patients who did not have renal disease, patients with non-end-stage chronic kidney disease had an increased risk of stroke or systemic thromboembolism (hazard ratio, 1.49; 95% confidence interval [CI], 1.38 to 1.59; P<0.001), as did those requiring renal-replacement therapy (hazard ratio, 1.83; 95% CI, 1.57 to 2.14; P<0.001); this risk was significantly decreased for both groups of patients with warfarin but not with aspirin. The risk of bleeding was also increased among patients who had non-end-stage chronic kidney disease or required renal-replacement therapy and was further increased with warfarin, aspirin, or both. Chronic kidney disease was associated with an increased risk of stroke or systemic thromboembolism and bleeding among patients with atrial fibrillation. Warfarin treatment was associated with a decreased risk of stroke or systemic thromboembolism among patients with chronic kidney disease, whereas warfarin and aspirin were associated with an increased risk of bleeding. (Funded by the Lundbeck Foundation.).

Chronic kidney disease, defined as a reduced glomerular filtration rate or increased urinary albumin excretion, is recognised as a rapidly growing global health burden, and increasing evidence suggests that it contributes to the risk and severity of cerebrovascular diseases. In particular, chronic kidney disease is an established risk factor for stroke and is also strongly associated with subclinical cerebrovascular abnormalities and cognitive impairment, partly because it shares several traditional and non-traditional risk factors, and sometimes uraemia-related and dialysis-related factors, with cerebrovascular diseases. The effect of chronic kidney disease on incident stroke differs among regions and races and is greater in Asian than in non-Asian people. Chronic kidney disease seems to be predictive of severe neurological deficits and poor vital and functional outcomes after both ischaemic and haemorrhagic strokes, which is partly due to the limitations of pharmacotherapies, including limited use and effects of novel oral anticoagulants, other antithrombotic treatments, and reperfusion treatment for hyperacute ischaemic stroke. In view of the strong two-way association between stroke and kidney disease, the pathophysiological interactions between the brain and kidney should be the subject of intensive study.

Clinical practice guidelines recommend using equations for estimating glomerular filtration rate (GFR) in chronic kidney disease (CKD) management and research. The MDRD (Modification of Diet in Renal Disease) Study and CKD-EPI (CKD Epidemiology Collaboration) equations originally were derived from a North American population and had an ethnic coefficient adjustment for African Americans. A Chinese coefficient for the MDRD Study equation subsequently was determined, but this has not been externally validated. We compared the accuracy of the equations, evaluated the ethnic coefficients, and assessed the equations for disease staging in a multiethnic Asian population with CKD. A diagnostic test study comparing the Asian coefficient (and subgroups)-modified MDRD Study and CKD-EPI equations and a cross-sectional study assessing disease staging. 232 outpatients (52% men; 40.5% Chinese, 32% Malay, and 27.5% Indian/other) with stable CKD. Asian and ethnicity-based modifications of the MDRD Study and CKD-EPI equations. Measured GFR using 3-sample plasma clearance of technetium-99m diethylenetriaminepentaacetic acid ((99m)Tc-DTPA), calculated using the slope-intercept method, with body surface area normalization (du Bois) and Brochner-Mortensen correction. Overall, the CKD-EPI equation is more accurate than the MDRD Study equation throughout the GFR range, with improved bias (median difference of estimated GFR - measured GFR) and root mean square error (P <0.001). CKD-EPI versus MDRD Study equation: bias, 1.1 ± 13.8 vs -1.0 ± 15.2 mL/min/1.73 m(2); precision, 12.1 vs 12.2 mL/min/1.73 m(2). Ethnic coefficients did not improve estimates of GFR significantly. The correctness of staging was improved using the CKD-EPI equation. All participants had CKD, but few were of European descent. The reference GFR technique was different from the original studies. The CKD-EPI is more accurate than the MDRD Study equation, particularly at higher GFRs. Therefore, we recommend adopting the CKD-EPI equation without ethnic adjustment for estimating GFR in multiethnic Asian patients with CKD. Copyright © 2011 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.