From June 2008 to July 2011 , 210 patients with chronic atrial fibrillation and rheumatic heart disease were randomized : ( 1 ) control group , patients underwent only valve replacement followed by amiodarone for rhythm control , ( 2 ) left atrial group ( LA group ) , patients underwent valve replacement and left atrial mono-polar radiofrequency ablation , ( 3 ) bi-atrial group ( BA group ) , patients underwent valve replacement and bi-atrial mono-polar radiofrequency ablation .