A Marc Gillinov (Department of Thoracic and Cardiovascular Surgery, Cleveland Clinic Foundation, Cleveland, USA) and others report in The New England Journal of Medicine that the combination of surgical atrial fibrillation ablation and mitral valve surgery in patients with persistent or long-standing persistent atrial fibrillation is associated with a significantly increased rate of freedom from atrial fibrillation at one year. However, it is also associated with a significantly increased rate of pacemaker implantation.
Gillinov et al report that atrial fibrillation is present in 30–50% of patients who undergo mitral valve surgery. They add that performing surgical atrial fibrillation ablation during mitral valve surgery in these patients during mitral valve surgery could potentially improve long-term outcomes, but say that the effectiveness and safety of such an approach “have not been rigorously established”. Therefore the aim of their study was to compare mitral valve surgery plus surgical atrial fibrillation ablation with mitral valve surgery alone in patients with persistent or long-standing persistent atrial fibrillation. In the mitral valve surgery plus ablation group, the authors also compared pulmonary vein isolation with the biatrial maze procedure. They explain that although pulmonary vein isolation is used more frequently than the biatrial maze procedure, data for the comparative effectiveness of the two procedures are limited.
Overall, 260 patients were randomised to undergo mitral valve surgery plus ablation (133) or to undergo mitral valve surgery alone (127 patients). Of those in the mitral valve surgery plus ablation group, 67 were randomly assigned to pulmonary vein isolation and 66 were randomly assigned to the biatrial maze procedure.
For both comparisons, the primary efficacy endpoint was the freedom from atrial fibrillation at both six months and at 12 months after the surgical procedures and the primary safety endpoint was a composite of outcomes including death, stroke, heart failure and myocardial infarction. Secondary endpoints included a composite of major cardiac or cerebrovascular adverse events, mortality, the need for rhythm-related interventions and quality of life.
Mitral valve surgery plus ablation was associated with a significant increase in the rate of freedom from atrial fibrillation at both six and 12 months (63.2% vs. 29.4% for mitral valve surgery alone at 12 months; p<0.001), and it was also associated with significantly fewer at least daily episodes of atrial fibrillation (19.8% vs. 45.2%, respectively; p<0.001).
There were no significant differences between groups in the rate of the primary safety endpoint, but mitral valve surgery plus ablation was associated with a significantly increased rate of pacemaker implantation at one year: 21.5 per 100 patients years vs. 8.1 per 100 patient years for mitral valve surgery alone (p=0.01).
About the increased rate of pacemaker implantation observed in the mitral valve surgery plus ablation group, the authors said that the rate was higher than that reported in “most studies but similar to that observed in a recent study. This relatively higher rate may be attributable in part to the fact that approximately 50% of the patients who underwent ablation had multivalve surgery, which increases the risk of atrioventricular block.” They add that about 40% of the patients in this group underwent valve replacement surgery and 50% were aged older than 70 years-“factors that also increase the risk of postoperative atrioventricular block”.
Gillinov et al did not find any significant differences in any of the study’s endpoints between pulmonary vein isolation and the biatrial maze procedure, with the authors noting that most observational studies suggest that the latter procedure is superior to pulmonary vein isolation in patients with persistent or long-standing persistent atrial fibrillation. However, they comment: “This trial was not planned to have power to distinguish between these two methods, however, and it is possible that a larger trial might identify a clinically meaningful difference.”
The authors conclude: “Establishing the effects of ablation on long-term survival, stroke incidence, the need for rehospitalisation, repeat rhythm procedures, and freedom from anticoagulation therapy requires further study.“