SAN FRANCISCO — The classic cut-and-sew Cox-Maze procedure is considered the definitive method for ablation of atrial fibrillation—the benchmark therapy to which a host of emerging innovative percutaneous and surgical ablative approaches must be compared. So just how good is it?
Not as great as open-heart surgeons and their patients would like to think, according to A. Marc Gillinov, M.D., surgical director of the atrial fibrillation (AF) program at the Cleveland Clinic Foundation.
Indeed, his retrospective study of 263 patients who underwent combined mitral valve surgery and a Cox-Maze procedure at the clinic showed ablation failure rates of 17% and 34% at 1 year and 3 years, respectively, he reported at the annual meeting of the American Association for Thoracic Surgery.
Ablation failure was defined by one or more episodes of AF occurring more than 6 months post surgery. Operative mortality was 1.9%. At 5 years, the prevalence of AF was 9%. Recurrent AF was electrically documented via a total of 2,367 ECGs during a median 2.6 years of follow-up.
Independent risk factors for recurrence of AF following Cox-Maze surgery were longer preoperative duration of the arrhythmia, greater left atrial size, patient age, and left ventricular mass index, Dr. Gillinov continued.
“We draw certain inferences from these data. It's possible that results would be enhanced by earlier operation after the development of atrial fibrillation. In addition, left atrial size reduction may improve results in patients with left atrial dilatation. Perhaps most importantly, these data teach us that close long-term follow-up of heart rhythm is necessary after ablation,” he observed.
The recurrence rates documented in this study are actually underestimates; as yet, no method exists for continuously monitoring heart rhythm month in and month out. It's sorely needed, Dr. Gillinov said.
“This is really the only methodology that will enable us to state with absolute confidence that at least until the point of follow-up we have achieved a cure,” he noted. “In addition, continuous monitoring will enable us to calculate the atrial fibrillation burden—the percentage of time a given patient is in atrial fibrillation—and we believe that this will turn out to be a clinically useful index of success or failure of the procedure.”
Although there was no control group in this series, 74% of participants presented for surgery in permanent AF—that is, continuous AF that was always present. Three years after surgery, only 10% of patients were on antiarrhythmic agents.
Dr. Gillinov said that although very few patients in this series underwent left atrial size reduction, in the last year or two, surgeons at the Cleveland Clinic have become much more aggressive in pursuing this strategy.
“What we do now is, if the left atrium is 6 cm or greater as measured by echo in any dimension, we will cut out a portion,” the surgeon explained.
All patients underwent removal of their left atrial appendage—the most common source of thromboemboli—at the time of the Cox-Maze procedure. Dr. Gillinov and his colleagues have been studying these appendages and the left atria to which they were attached, for more than a decade in an effort to better understand the arrhythmia.
“What we find is that in people with very-long-term atrial fibrillation—which correlates with an enlarged left atrium and permanent atrial fibrillation—their atria have an intense inflammatory reaction, scar, and fibrosis. I think what that patient brings to the operating room may make it such that we can never restore sinus rhythm, at least not permanently, even with the operation done correctly,” he said. “A strategy of long-term antiarrhythmic therapy may improve our results in those patients.”