1. Introduction
Up to 50% of patients undergoing mitral valve (MV) surgery experience preoperative atrial fibrillation (AF) 1. Incidence of stroke in patients with AF who are optimally anticoagulated remains between 2-5% per year, depending on the individual risk factors2. Surgical ablation during MV surgery has now been clearly shown to be associated with a reduced 30-day mortality and stroke and is recommended at the time of concomitant mitral operations to restore sinus rhythm 1,3-6. While there have been many studies on concomitant surgical ablation in cardiac surgery, analysis of mid-term or long-term outcomes of simultaneous Cox-Maze procedure or pulmonary vein isolation (PVI) during MV surgery is still lacking.1,5 The performance rate of concomitant surgical ablation in patients with AF at the time of MV surgery has risen from 52% to 62% over the last decade7.
The first maze procedure (Cox-Maze I) was performed by James Cox on September 25, 1987 8. The procedure evolved into the Cox-Maze III and became the gold standard surgical treatment of AF3,9. In 2002, Damiano and associates have modified the Cox-Maze III technique and replaced the majority of the incisions with a combination of bipolar radiofrequency (RF) and cryothermal ablation lines in a procedure termed the Cox-Maze IV, which has shortened and simplified the operation and has decreased morbidity and mortality10. The Cox-Maze IV is currently the gold standard surgical treatment for AF, with estimated freedom from AF and from antiarrhythmic drugs (AAD) at 1 year postoperatively of 93% and 85%, respectively 11. However, concomitant pulmonary vein isolation (PVI) is still being used more frequently than the Cox-Maze procedure as it is the simplest and most rapidly completed set of ablation lesions 12. In addition, PVI can be performed without cardiopulmonary bypass in coronary artery bypass graft surgery13.
In the attempt to evaluate mid-term efficacy and safety of concomitant Cox-Maze relative to PVI in patients with AF undergoing MV surgery, we conducted a systematic review to critically evaluate randomized controlled trials (RCTs) and non-randomized studies directly comparing the two procedures in this setting with additional subgroup meta-analysis of RCTs.