Changes in estimated glomerular filtration rate before and after the first visit for atrial fibrillation.

Background: Although the development of atrial fibrillation (AF) and the progression of chronic kidney disease are known to be interrelated, it remains unclear when and how renal function changes during the clinical course of AF.

Methods: This study retrospectively enrolled 131 patients who were able to collect data on estimated glomerular filtration rate (eGFR) at least five times during the 500 days before and 500 days after the first visit (baseline) of new-onset AF, respectively. To investigate the temporal relationship between the development of AF and the beginning of worsening renal function (WRF), a piecewise regression model was applied to the eGFR time series data. The time point at which the slopes of the two regression lines changed (inflection -point), the slope before and after the inflection-point (β1 and β2, respectively), and the difference in slope (Δβ) were estimated. The presence of WRF was defined as having the inflection-point at which both Δβ and β2 were < - 0.0083 mL/min/1.73 m/day (corresponding to 3.03 mL/min/1.73 m/year), and the corresponding the inflection-point was defined as the beginning of WRF.

Results: WRF was detected in 54 (41.2%) patients. The beginning of WRF were distributed at various times, but most frequently (23 of 54 patients) within 100 days before and after baseline. The presence of WRF was not associated with age, heart failure, or baseline eGFR, but was associated with positive β1 (odds ratio 30.5, 95% confidence interval 11.1-83.9, P < 0.01).

Conclusion: In nearly half of AF patients with WRF, the beginning of WRF was observed within a few months before or after the first visit for AF. Patients with a positive eGFR slope before the onset of AF are more likely to develop WRF after the onset of AF, suggesting that potential kidney damage may be underlying.