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.