Objective As the efficacy of surgical ablation for atrial fibrillation (AF) is reported to be suboptimal for patients with a giant left atrium (LA), its routine use on this population has remained controversial. We sought to evaluate the clinical outcomes of patients with a giant LA undergoing mitral valve (MV) surgery with/without the maze procedure.

Methods We identified 759 patients with a giant LA (>60 mm) and AF undergoing MV surgery from 1999 through 2012. Of these, 400 underwent MV surgery with the maze procedure (maze group), and the remainder (n=359) underwent MV surgery only (no-maze group). To reduce the impact of selection bias, propensity score analyses were performed based on 25 baseline covariates.

Results Early death occurred in five (1.3%) and nine (2.5%) patients in the maze and the no-maze group, respectively (p=0.28). Freedom from AF at 5 years was 68.9% in the maze group and 9.6% in the no-maze group (p<0.001). After adjustment, the maze group showed a significantly lower risk of death (HR, 0.65; 95% CI 0.44 to 0.98; p=0.038), thromboembolic events (HR, 0.23; 95% CI 0.09 to 0.58; p=0.002) and composite adverse outcomes (death, congestive heart failure and valve-related complications; HR, 0.55; 95% CI 0.42 to 0.71; p<0.001) than the no-maze group. In subgroup analyses, MV surgery with the maze procedure resulted in higher survival and event-free survival in most risk subgroups than without the maze procedure.

Conclusions The concomitant maze procedure improved postoperative rhythm status, clinical outcomes and cardiac functions in patients with a giant LA undergoing MV surgery. This study indicates that the patients with a giant LA undergoing MV surgery may benefit from an addition of the maze procedure.