The relationship between serum indoxyl sulfate and the renal function after catheter ablation of atrial fibrillation in patients with mild renal dysfunction

Indoxyl sulfate (IS), a protein-bound uremic toxin, induces renal disorders and atrial fibrillation (AF). It is well known that renal dysfunction is a risk factor for AF and radiofrequency catheter ablation (RFCA) improves the renal function. However, the improvement in the renal function after RFCA in patients with early stage chronic kidney disease (CKD) and the serial changes in the IS level have not been fully elucidated. This study aimed to investigate whether IS affects the improvement in the renal function. A total of 91 consecutive patients with mild kidney dysfunction (CKD stage I-II) who underwent RFCA and maintained sinus rhythm were prospectively enrolled. The plasma IS level and estimated glomerular filtration rate (eGFR) were determined before, 3months, and 1year after RFCA. The patients were divided according to the IS quartiles (Q1-4; < 0.4, 0.4-0.7, 0.7-1.2, and > 1.2g/ml). There was no significant difference in the eGFR among the IS quartiles. A significantly higher eGFR improvement rate was obtained for IS-Q4 than the other quartiles (p=0.039). The IS-Q4 IS level significantly decreased at 1year after RFCA (1.8 +/- 0.8 to 1.2 +/- 0.7g/ml, p<0.01). The multivariable logistic model revealed that a high-IS level (IS-Q4) was an independent predictor of an eGFR improvement (OR 3.33; 95% CI 1.16-9.59; p=0.026). A high-IS level reduction after RFCA improved the renal function in AF patients with mild kidney dysfunction.