Conference Coverage

Not all AF maze operations are aMAZE-ing


 

REPORTING FROM ACC SNOWMASS 2019

– The term “maze procedure” for surgical ablation of atrial fibrillation is bandied about rather loosely these days, but as far as Hartzell V. Schaff, MD, is concerned, the operation of choice remains the classic cut-and-sew maze III procedure developed by James L. Cox, MD, while at Washington University, St. Louis.

Dr. Hartzell V. Schaff professor of surgery, Mayo Clinic, Rochester, Minnesota Bruce Jancin/MDedge News

Dr. Hartzell V. Schaff

“The classic Cox maze III, the cut-and-sew maze, is the best procedure for getting rid of atrial fibrillation and is in my view the gold standard. The advantage of the Cox maze, I think, is there’s no issue of transmurality. Some people argue that transmurality isn’t important, but it can occur because of gap lesions,” he said at the Annual Cardiovascular Conference at Snowmass sponsored by the American College of Cardiology.

Unlike modifications of the Cox maze III – such as the mini maze or the maze IV, which utilizes radiofrequency energy or cryoablation to create scars in an effort to achieve pulmonary vein isolation – the maze III cannot be done as a minimally invasive procedure. After all, it requires making incisions in both atria, along with aortic cross-clamping and cardiopulmonary bypass. But it has a significantly higher long-term rate of freedom from recurrent atrial fibrillation (AF) than the other operations. And crucially, it enables the surgeon to readily obliterate the left atrial appendage.

“The most important thing when you do any surgical procedure for atrial fibrillation, I think, is getting rid of the left atrial appendage. When you do cut-and-sew maze, that’s done 100% of the time,” explained Dr. Schaff, professor of surgery at the Mayo Clinic in Rochester, Minn.

“We really have a lot of work left to do as surgeons in improving the outcome of surgery for atrial fibrillation. One of the things we as surgeons don’t do well is getting rid of the left atrial appendage. This ought to be done in every patient that has surgical ablation for atrial fibrillation,” according to the cardiothoracic surgeon.

And yet, he continued, in a series of nearly 87,000 patients with AF who underwent nonemergent cardiac surgery in the Society of Thoracic Surgeons database, 48.0% of whom underwent surgical ablation for AF, only 63.9% of those who had standalone ablation for lone AF got their left atrial appendage dealt with, compared with 86%-89% of those who underwent concomitant cardiac surgery, such as mitral valve repair or replacement (Ann Thorac Surg. 2017 Aug;104[2]:493-500).

“That’s awful, really. And the reason for that low left atrial appendage obliteration rate is this: For many of those patients who had surgery for lone atrial fibrillation, the surgeons were trying to do minimally invasive surgery, where they do pulmonary vein isolation on the right side, so they don’t have access to the left atrial appendage,” Dr. Schaff said.

“In the past,” he recalled, “we would ligate the left atrial appendage. Nowadays because of echocardiographic studies that show there’s persistent patency in a sizable percentage of patients, we amputate the left atrial appendage in almost all of the patients.”

The terminology surrounding surgical ablation for AF, in his view, has become rather confusing. “Most of you, when you refer a patient for surgical ablation for AF, the surgeons will just say they do a maze procedure,” Dr. Schaff cautioned. “Somehow, all of that [maze IV, mini maze] today is lumped together as a classic maze procedure, but it’s really not. We have different lesion sets and energy sources.”

And different outcomes as well. In a series of 1,189 adults who underwent surgical ablation for AF at the Mayo Clinic, of whom 44% had a biatrial cut-and-sew maze while the rest had surgical cryotherapy, radiofrequency ablation, or a combination of the two, the rate of freedom from AF 1 year post surgery was 85% with the cut-and-sew maze versus 71% with the alternatives. At 5 years or more, the rates were 78% and 52%, respectively. In a multivariate analysis, freedom from AF was independently associated with preoperative paroxysmal rather than permanent AF, performance of the classic maze III procedure, concomitant treatment of associated mitral valve disease, and younger age.

Moreover, rates of the major early postoperative complications – stroke, bleeding, and renal failure – were similar in the cut-and-sew maze III and other groups.

“So a lesser procedure doesn’t necessarily mean fewer complications,” Dr. Schaff noted.

One of the criticisms levied against the maze III is that it’s too much surgery for AF. But it’s actually relatively inexpensive because the disposables – suture, needles, scalpel – are those used in the commonly performed concomitant cardiac surgical procedures. “The Cox maze III does take extra time, but with experience it’s not much extra time,” he asserted.

Indeed, in a series of 452 Mayo Clinic maze III patients, the cross-clamp and cardiopulmonary bypass times were 52 and 73 minutes, respectively, for those undergoing an isolated maze III, compared with 73 and 86 minutes for patients whose maze III was done in conjunction with other procedures, most commonly mitral valve repair or replacement.

An underrecognized group of patients who benefit from a standalone cut-and-sew maze are those with tachycardia-induced cardiomyopathy marked by AF or atrial flutter, rapid uncontrolled ventricular response, a decreased left ventricular ejection fraction, and no associated valvular or congenital heart disease. In a series of 37 such patients identified and treated with a maze III operation at the Mayo Clinic, their average preoperative left ventricular ejection fraction of 43% improved to about 55% at discharge, a benefit sustained at last follow-up a median of 63 months later. The outcome was particularly impressive in the 11 patients with a severely depressed left ventricular ejection fraction averaging 31% preoperatively, which jumped to 53% at discharge (Ann Thorac Surg. 2006 Aug;82[2]:494-500).

“Their ejection fraction goes up when you control the tachycardia-induced cardiomyopathy,” he observed. “So reduced left ventricular ejection fraction may be an indication for surgery rather than a contraindication.”

Dr. Schaff emphasized that it’s important for cardiologists and surgeons not to overpromise what surgical ablation of AF can accomplish. The only randomized trial of surgical ablation of AF versus no ablation during mitral valve surgery, sponsored by the National Institutes of Health and Canadian Institutes of Health Research and carried out by the Cardiothoracic Surgical Trials Network, showed no significant between-group differences at 1 year in any of numerous quality of life measures, nor was there a survival benefit for ablation (N Engl J Med. 2015 Apr 9;372(15):1399-409).

“We must point out that there’s no indication that controlling atrial fibrillation has anything to do with improving survival. It has to do with symptomatic benefit and perhaps reducing risk of stroke,” he said.

Dr. Schaff reported having no financial conflicts regarding his presentation.

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