Kidney function monitoring and trajectories in patients with atrial fibrillation

Background Atrial fibrillation (AF) and chronic kidney disease (CKD) frequently co-exist. The frequency of kidney monitoring and range of kidney function in patients with AF in clinical practice are uncertain. Methods All adult Albertans with AF between 2008 and 2017 were identified using ICD-9 and -10 codes 427.3 and I48. Kidney Disease Improving Global Outcomes (KDIGO) risk categories were defined using eGFR by the Chronic Kidney Disease Epidemiology Collaborative equation and albuminuria results within 6 months of eGFR measurement. eGFR trajectories were compared from baseline to maximum value within the following year. Results Among 105,946 patients with AF, 16.0% were KDIGO category G1 (eGFR ≥ 90), 49.0% G2 (60–89.9), 19.8% G3a (45–59.9), 11.4% G3b (30–44.9), and G4 3.8% (15–29.9). Albuminuria was normal/mild 83.4%, moderate 11.7%, and severe 4.9%. Kidney monitoring was more common among people with lower eGFR and worse albuminuria, from approximately twice annually for G1-2/A1-2 to 8 times annually in stage G4A3. Approximately 60–80% of patients received guideline-recommended monitoring, consistent across KDIGO stages. With lower baseline eGFR, annual change in eGFR decreased while the relative proportion of patients who worsened compared to improved increased: for baseline eGFR 60–89.9, 16.7% worsened vs 6.7% improved, but for eGFR 30–44.9, 8.8% worsened but only 1.0% improved. Conclusion The frequency of kidney function monitoring in patients with AF increased with worsening KDIGO risk category and adhered to KDIGO guidelines in approximately three quarters of patients. A minority of patients had moderate to severe eGFR impairment, of whom most remained stable over 1 year.