Surgical ablation of atrial fibrillation--when, why, and how?

In 1987, Dr. James L. Cox performed the first maze procedure for surgical ablation of atrial fibrillation.1 Previous efforts at surgical correction were not uniformly successful, and some procedures corrected cardiac rhythm but did not restore synchronized atrial contraction. Cox’s maze procedure, performed with a precise pattern of incisions and suturing of the right and left atria, proved highly successful in restoring sinus rhythm and, in many patients, reestablishing atrial transport function. There is, however, a lack of consensus regarding indications for surgical ablation of atrial fibrillation. In patients with structural heart disease, atrial fibrillation is a common coexisting problem, and ablation can be performed concomitantly with valvular surgery and correction of congenital defects. To lessen the additional time required to perform the standard maze III procedure, surgeons have developed simplified atrial lesion sets, focused on isolating the orifices of the pulmonary veins, and used alternative energy sources to create atrial ablation lines to minimize the durations of ischemic time and cardiopulmonary bypass. Unfortunately, wide variability in surgical methods and the heterogeneity of patients with atrial fibrillation have contributed to controversies of when, why, and how adjunctive surgical ablation should be applied.2 With this background, it is evident that rigorously controlled, prospective evaluations of surgical ablation would be welcome, and the report by Gillinov and associates of their randomized study of adjunctive surgical ablation, now published in the Journal, clarifies some issues.3 The principal aim of the study was modest — to determine the effectiveness of surgical ablation of atrial fibrillation in patients undergoing mitralvalve repair or replacement. Among study patients with preoperative persistent or long-standing persistent atrial fibrillation, the addition of an ablation procedure to mitral-valve surgery increased the rate of freedom from atrial fibrillation at both 6 months and 12 months postoperatively from 29.4% (the rate among controls) to 63.2% (P<0.001), with similar early mortality in the two groups. As the authors discuss, this improvement in freedom from atrial fibrillation is consistent with the findings of many previous nonrandomized and randomized studies. Strict assessment of cardiac rhythm with 3-day continuous Holter monitoring at 6 months and 12 months may explain the lower apparent success rate in the ablation group as compared with the 80 to 90% rate of freedom from atrial fibrillation 1 year postoperatively in larger, nonrandomized, single-center studies.4,5 The decision to perform concomitant surgical ablation of atrial fibrillation, however, depends not only on confirmation of early safety and effectiveness, but also on clinical benefit. In this randomized study, there was no significant difference in secondary end points of functional class, quality-of-life measures, or medication use between patients who had atrial fibrillation ablated at the time of mitral-valve surgery and those who had mitral-valve operations alone. The authors point out that the investigation was not powered to detect differences in the individual or composite end points, but readers will notice the absence of even a trend toward fewer major cardiac or cerebrovascular adverse events in patients undergoing concomitant ablation of atrial fibrillation. This puzzling finding is explained in part by the study population, which included many older patients (average age, >69 years) as well as patients who underwent mitral-valve replacement (44%) and patients who had addition-