What size of left atrium significantly impairs the success of maze surgery for atrial fibrillation?

A best evidence topic in cardiothoracic surgery was written according to a structured protocol. The question addressed was in adults with atrial fibrillation (AF), what preoperative size of left atrium impairs maze surgery success in terms of recurrence of AF. Altogether 422 papers were found using the reported search, of which 12 represented the best evidence to answer the clinical question. The authors, journal. date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. Nine of 12 papers found that preoperative left atrial (LA) size was significantly larger in patients who experienced recurrent AF. When left atrial diameter (LAD) was found to be statistically different between sinus conversion and recurrent AF groups the mean LAD was consistently >60 mm in the recurrent AF group, whereas it was <60 mm in all but one of the sinus conversion groups. In terms of a cut-off value for LA size, a left atrial volume index >135 ml/m(2) was found to confer 100% specificity for maze failure and a LAD >60 mm was found to be 100% sensitive for maze failure. A preoperative LAD <48.3 mm was shown in one study to be 100% sensitive for sinus conversion by the maze procedure. Despite much evidence highlighting preoperative LAD as a risk factor for maze failure, relatively few studies seek to define a definitive cut-off value for LA size beyond which the risks of the procedure (such as bleeding, infection or stroke) outweigh the chance of sinus recovery. We conclude that since mean preoperative LAD in AF groups is consistently over 60 mm caution should be exercised when offering these patients the maze procedure. Furthermore, the relationship between preoperative LAD and maze failure appears continuous and so patients should be counselled as to their increased risk of failure the further they deviate from a LAD of 60 mm. There is some evidence for and no available evidence to the contrary that a LAD < 43 mm is associated with complete maze success. Hence, these patients should be offered the maze procedure unless there are alternate strong contraindications.