#377 Assessment of kidney function by creatinine and cystatin C and cardiovascular outcomes in patients with atrial fibrillation

Abstract Background and Aims Atrial fibrillation (AF) in patients with chronic kidney disease are at an increased risk for ischemic and bleeding events and all-cause mortality. Accurate kidney function estimation is key for risk assessment. Creatinine is commonly used to calculate the Glomerular Filtration Rate (GFR). However, cystatin C has been described to be more sensitive than creatinine independent of muscle mass, autoimmune disease, inflammation or consuming diseases. Our aim was to evaluate the associations between kidney function, assessed by creatinine and cystatin C, and cardiovascular events (CVE), its individual components, and major bleedings. Method We enrolled 326 AF patients into two prospective, multicenter cohort studies. Creatinine and cystatin C were measured at baseline and clinical outcome events were assessed yearly. We calculated GFR using the Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI] formula based on either creatinine (GFRcr), cystatin C (GFRcy) or both (GFRc2). Primary outcome was major CVE, defined as a composite of stroke or systemic embolism, myocardial infarction and cardiovascular death. Secondary outcomes were the individual components of major CVE and major bleeding. Multivariable adjusted Cox regression analyses were built to evaluate the associations between kidney function and outcome events. Results Mean age was 56 ± 9 years and 37% were female. Mean creatinine and cystatin С levels were 112 ± 21 μmol/l and 1.6 ± 0.3 mg/l, respectively, translating to a GFRc2 of 58.2 ± 16.8 ml/min/1.73 m2. Over a median follow-up of 2 years, the incidence rates for major CVE (per 100 person-years) across quartiles (Q1-Q4) of GFRc2 were 23.1, 20.3, 17.6 and 14.7, respectively. When using multivariable adjusted Cox regression analysis, major CVE was significantly associated with GFRcr (per 1 standard deviation: HR 0.89 (95% CI 0.79; 0.98) p = 0.01), GFRcy (HR 0.65 (CI 0.53; 0.72), p < 0.001) and GFRc2 (HR 0.74 (CI 0.63; 0.82), p < 0.001). This association was mainly driven by cardiovascular death. Major bleeding was associated with GFRcy (HR 0.78 (0.64-0.93) p = 0.001) and GFRc2 (HR 0.82 (0.69-0.97), p = 0.01), but not with GFRcr (HR 0.93 (95% CI 0.83-1.1) p = 0.33). Conclusion Among AF patients, GFR equations including cystatin C were associated both with major CVE and bleeding events, while creatinine based GFR equations were only associated with major CVE. Therefore, Cystatin C based GFR equations might offer more comprehensive risk stratification in patients with AF.