PRAGUE-12: Surgical Ablation With Maze Procedure Restores Sinus Rhythm in AF Patients

August 28, 2012

August 28, 2012 (Munich, Germany) — Surgical ablation when added to cardiac and/or valvular surgery in patients with atrial fibrillation (AF) results in significantly more patients being in normal sinus rhythm compared with patients who undergo surgery without the modified maze ablation procedure, research shows [1].

Interestingly, the benefit was driven by patients with longstanding, persistent AF. At one year, 53.2% of these patients who underwent the maze procedure in addition to surgery were in normal sinus rhythm, compared with just 13.9% of patients who underwent surgery alone. In contrast, there was no difference in the rates of sinus rhythm between the two treatment arms in patients with paroxysmal or persistent AF.

There was no significant difference in the primary safety outcome, a 30-day composite of death, MI, stroke, and renal failure; 10.3% of patients who underwent the maze procedure during surgery experienced an adverse event compared with 14.7% of patients who underwent cardiac surgery only.

Dr Petr Widimsky

"The idea for the study arose during our daily heart meetings," senior investigator Dr Petr Widimsky (Charles University, Prague, Czech Republic) told heartwire . "We meet every day with cardiac surgeons and discuss our patients. When we talk about patients with AF going for bypass surgery, we always talk about whether they should get the maze procedure or not. Personally, I was very conservative. I was very restrictive, saying, 'Why maze? It's not been proven.' It makes a scar in atria, and there was never any proof of its safety. Also, it prolongs the surgical procedure. So I was very skeptical about it."

Based on the results of the study, known as PRAGUE-12, which were presented here today at the European Society of Cardiology (ESC) 2012 Congress and published simultaneously in the European Heart Journal, Widimsky told heartwire : "We can say now that the procedure is safe and that it restores sinus rhythm, but we still can't say whether it helps patients clinically in the long term."

Drs Gerhard Hindricks and Christopher Piorkowski (University Leipzig Heart Center, Germany), however, are far from convinced about the benefits of Maze on sinus rhythm. In an editorial [2], they take issue with the use of 24-hour Holter ECG monitoring for a rhythm-based primary-outcome parameter, saying that the follow-up regimen is not enough to formulate reliable and solid results.

In this light, the rhythm-outcome data reported in the PRAGUE-12 study are of very limited value.

"Indeed, according to current knowledge and a huge set of valid scientific data, it must be expected that with such weak follow-up, approximately 70% of all AF recurrences may have been missed," write Hindricks and Piorkowski. "Thus, the true AF recurrence rate certainly was significantly higher than reported. The main reason for this is the well-documented and extremely high incidence of asymptomatic AF episodes. In this light, the rhythm-outcome data reported in the PRAGUE-12 study are of very limited value."

Commenting on the study results, cardiac surgeon Dr Miguel Sousa Uva (Hospital da Cruz Vermelha Portuguesa, Lisbon, Portugal) told heartwire that, despite the discrepancies, the data are encouraging. Still, he added that the results are only preliminary given the current lack of data on hard clinical end points. He is satisfied, however, that the maze procedure restored patients to sinus rhythm and did so without any significant perioperative risks. While there was an increase in cardiopulmonary bypass time (28 minutes), cross-clamp time (27 minutes), and operation time (20 minutes), the increases were reasonable, he said.

"If you're trying to sell something to surgeons, you can't say we have a great procedure, but it's one hour longer on-pump," said Uva. "We know that it has an impact. Patients bleed more, and there are more incidences of renal insufficiency and pulmonary complications. So it's a compromise. You have to find a procedure that at the same time is safe and efficacious. And it seems this is. It shows it has the potential to increase the number of patients that go back to sinus rhythm."

To Maze or Not to Maze, That Is the Question

The PRAGUE-12 study was designed to test the hypothesis that surgical atrial ablation would restore sinus rhythm in 117 patients undergoing cardiac surgery (vs 107 patients who underwent surgery only). Although surgeons had the choice of using radiofrequency energy or cryoablation for the procedure, 97% of patients who underwent the modified maze procedure were treated with cryoablation.

Results showed that the maze procedure was effective in restoring sinus rhythm in the entire cohort. However, when stratified by type of AF, only those with longstanding, persistent AF appeared to benefit from the procedure. Rates of death, stroke, major bleeding, and hospitalization for heart failure were equivalent at one year in both study groups.

Percentage of Patients in Normal Sinus Rhythm After One Year

Patients Maze procedure with surgery (%) No maze procedure with surgery (%) p
All patients (n=224) 60.2 35.5 0.002
Paroxysmal AF 61.9 58.3 1.00
Persistent AF 72 50 0.194
Longstanding, persistent AF 53.2 13.9 <0.001

Regarding the lack of benefit in patients with paroxysmal AF, Widimsky said the unusual finding might be related to the methodology. The primary efficacy end point--sinus rhythm at one year--was assessed using 24-hour Holter monitoring.

In their editorial, Hindricks and Piorkowski aren't buying the explanation, noting that 24-hour Holter monitoring is more likely to miss recurrences of paroxysmal AF than longstanding, persistent AF, and this would have favored patients with paroxysmal and persistent AF [2].

They point out that the benefit in longstanding AF and the absence of benefit in paroxysmal and persistent AF runs counter to all previous reports on catheter or surgical ablation of AF. The most likely explanation for the lack of benefit in these patients might be technical, rather than methodological. They are critical of the cryoablation technique, suggesting that lack of benefit might be the result of inadequate isolation of the pulmonary veins. One previous study, they point out, suggested that cryoablation might not be sufficient to create transmural lesions.

The editorialists also say that care should be used with the current indication for surgical ablation in unselected and asymptomatic patients. The ESC guidelines for the management of AF say that surgical ablation "may be considered" in asymptomatic patients (class IIb recommendation, level of evidence C), but data from PRAGUE-12 suggest no benefit in the asymptomatic population. As a result of the trial, there are more questions than answers, state Hindricks and Piorkowski.

More Work Needs to Be Done

When asked if surgeons should consider the treatment of AF using the modified maze procedure only in patients with longstanding, persistent AF, Widimsky said that the researchers just don't know the answer.

"We have to do more studies on this," he told heartwire . "The observation we have is interesting and a little bit surprising to a certain extent, but we can't answer this question." He does suspect, however, that the results might increase the use of maze in patients with longstanding, persistent AF. In these patients, surgeons might have been reluctant to perform the maze procedure in the past if they believed the patient's longstanding arrhythmia was unlikely to be improved.

Commenting on the study, Dr Robert Hatala (National Heart Institute, Bratislava, Slovakia) told heartwire that the results, from his perspective as an electrophysiologist, are promising given the benefit in patients with longstanding, persistent AF. "This is a type of AF we have trouble ablating using radiofrequency catheter ablation," he said. "We are probably more successful with paroxysmal AF. So I would see this [modified maze] as a complement to the catheter approach for longstanding, permanent AF."

The study authors, editorialists, Uva, and Hatala report no conflicts of interest.