The study followed 24 end-stage renal disease patients on hemodialysis with a high-flow arteriovenous fistula (>1500 mL/min) and heart failure (NYHA ≥ II) who underwent surgical reduction of fistula flow. After the procedure, fistula flow decreased by about 50% (from a median of 2,525 [1,388] to 1,250 mL/min, p = 0.00006). The left atrial volume index significantly decreased from 44.7 ± 17.3 to 38.5 ± 15.4 ml/m² (p = 0.01). At the same time, left atrial systolic function, expressed as ejection fraction, improved from 49.6 ± 14.9% to 53.2 ± 13.5% (p = 0.046). Trachea either improved or completely disappeared in all patients after the procedure. Baseline left atrial ejection fraction was negatively correlated with age, left atrial volume index, and NYHA class, but no independent predictors of postoperative improvement in this ejection fraction were found. The authors conclude that surgical reduction of high-flow fistula flow leads to significant improvement in left atrial systolic function and reduction in left atrial volume in patients with high-output heart failure.