['The maze procedure for the treatment of atrial fibrillation (AF) is a widely used adjunctive therapy. It is necessary to define the precise indications for the procedure based on preoperative factors, but definitive parameters in terms of atrial function have not been well determined.', 'In the present study, 55 consecutive patients undergoing the maze procedure for persistent AF in combination with operations for organic heart diseases were evaluated. After dividing the patients into successful (n=41) and unsuccessful procedure (n=14) groups, based on the postoperative rhythm, the preoperative left atrial (LA) emptying fraction measured by transthoracic 2-dimensional echocardiogram was compared between groups. The LA emptying fraction was calculated as [(LA maximum volume - LA minimum volume)/LA maximum volume]x100. The preoperative LA emptying fraction was higher in the successful procedure group than in the unsuccessful procedure group (31.2+/-8.5 vs 21.4+/-10.9%, P=0.0011). Based on receiver-perating characteristic curve analyses, LA emptying fraction >26% predicted successful maze procedure with 70.7% sensitivity and 78.6% specificity.'] Is preoperative left atrial emptying fraction a powerful predictor of successful maze procedure?