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Left-Atrial MAZE Ablation Compromises Atrial Function

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Atrial Ablation Remains Best Despite Functional Impairment

It comes as no surprise that complete left-atrial ablation during cardiac surgery produces impaired left-atrial function, although it is surprising to see how much damage occurs. But this finding is no reason to abandon atrial ablation and replace it with less extensive treatment with pulmonary-vein isolation unless the reduced left-atrial function is shown to have a clear impact on patient outcomes or survival. Based on what we know today, on balance, it’s more important to more thoroughly and reliably address our patients’ atrial arrhythmia than it is to preserve full atrial function. Substituting pulmonary-vein isolation for full ablation would increase the risk of atrial fibrillation recurrence.

The study done by Dr. Compier and her associates in Leiden is the first to document the functional impact of complete left-atrial ablation using the modified Cox-MAZE procedure in such a careful and systematic way using echocardiography. But anyone who is concerned about the impact of full ablation on atrial function must acknowledge that this treatment is also very beneficial to patients. The Leiden group clearly showed that full ablation is very detrimental to the atrium, but they did not associate these impairments with adverse clinical outcomes. As far as we know, atrial fibrillation is a more important determinant of clinical outcome than are changes in left-atrial function.

Dr. Pierre Page

A major way in which full ablation differs from pulmonary vein isolation is the added isolation of the left-atrial appendage, and we know that contraction of the left atrium mostly depends on the left-atrial appendage. But isolation of the appendage also reduces the risk of stroke. Previously-reported findings from several studies have shown that pulmonary vein isolation is less effective at restoring sinus rhythm and preventing atrial fibrillation recurrence. Based on all the evidence collected so far, I will continue to preferentially use full ablation on most of my patients.

Dr. Pierre Page is chief of cardiac surgery at the University of Montreal. He had no disclosures. He made these comments in an interview.



LOS ANGELES – Full left-atrial ablation by the modified Cox MAZE procedure to treat atrial fibrillation led to significant reductions in left atrial function, based on a detailed assessment of 31 patients who underwent this treatment using bilateral bipolar radiofrequency.

The damaging effect of complete left-atrial ablation contrasted with the impact of a less extensive procedure, pulmonary vein isolation, which kept left-atrial function intact and even improved it by some parameters. Opinions split on the implications of these findings.

"Our advice is that left-atrial ablation should be restricted to those cases where pulmonary vein isolation will likely be insufficient" to restore and maintain sinus rhythm, Dr. Marieke G. Compier said as she presented the findings at the annual scientific sessions of the American Heart Association on Nov. 6.

But a cardiac surgeon who heard the results disagreed, contending that the top priority is performing the procedure that will result in durable prevention of atrial fibrillation (AF) recurrence.

"Recurrence of atrial fibrillation is a more important determinant of [successful] clinical outcomes than preserved atrial function," said Dr. Pierre Page, chief of cardiac surgery at the University of Montreal. "The data we have today show that left-atrial ablation is very beneficial," Dr. Page said in an interview.

Dr. Compier and her associates used echocardiography to assess left-atrial function in 31 patients who underwent a modified Cox-MAZE procedure for complete left-atrial ablation using bilateral bipolar radiofrequency, and 31 patients who underwent pulmonary-vein isolation (PVI) only. In the full ablation group, 25 patients had persistent AF and 6 had paroxysmal AF; in the PVI group, 25 patients had paroxysmal disease and 6 had persistent AF. All patients also underwent concurrent coronary artery bypass, valve surgery, or both.

The researchers assessed the efficacy of AF treatment using 24-hour ECG monitoring at 3, 6, and 12 months following surgery. They also used two-dimensional echocardiography to assess left atrial size and function at 3 months and 1 year after surgery.

After 1 year, 68% of the patients who had full ablation and 81% of those who underwent PVI were free of AF and completely off anti-arrhythmic drug treatment; the other patients in each group had AF recurrences. The different long-term success in maintaining sinus rhythm in the two groups probably stemmed from the unbalanced distribution of patients with paroxysmal and persistent AF, said Dr. Compier, a cardiologist in the Heart Center at Leiden (the Netherlands) University Medical Center. "I think this is why full ablation seemed less successful," she said.

After 1 year, echocardiographic examinations showed that patients treated with full ablation had statistically significant reductions in left atrial volume and strain, and 42% of patients had A-wave restoration. Compared with measurements made prior to surgery, strain rate fell by an average of about 50%, peak A-wave dropped by an average of about a third, and average left-atrial ejection fraction and filling fraction each dropped by about 20%. All of these changes were statistically significant, compared with baseline.

In contrast, patients who underwent PVI had no significant change in their strain rate or peak A wave, and their average left-atrial ejection fraction and filling fraction each rose by about 10% compared with baseline, statistically significant differences. A-wave restoration occurred in 87% of the PVI patients.

Stepwise regression analysis of baseline differences between the two study groups showed that the follow-up differences seen in left-atrial size and function were best explained by the different ablation treatments the two groups received, Dr. Compier said.

Dr. Compier said that she had no disclosures.

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