Success up as LA Size Declines for RF Ablation at Cardiac Surgery

May 01, 2012

May 1, 2012 (San Francisco, California) — Success with the Cox-maze IV radiofrequency (RF) ablation procedure for persistent atrial fibrillation (AF) [1], performed at the same session with cardiac surgeries like CABG or valve repair, is more likely the smaller the patient's left-atrial (LA) diameter. But the risk of AF recurrence rises with complexity of the cardiac surgery--as, for example, when two or more valves are repaired compared with only one.

So suggests the prospective, multicenter Concomitant Utilization of Radio Frequency Energy for Atrial Fibrillation (CURE-AF) study [2], which also had lessons to teach about difficulties in conducting clinical trials of surgical procedures. In this case, its success--in terms of how many patients stayed AF-free and off antiarrhythmic drug therapy--varied widely among the trial's 15 US centers.

Dr Ralph J Damiano Jr

Success rates ranged from 33% at one center to 100% at three centers, according to Dr Ralph J Damiano Jr (Washington University School of Medicine, St Louis, MO), who presented CURE-AF here at the American Association of Thoracic Surgery 2012 Annual Meeting. The differences probably weren't due to varying patient or institutional characteristics, as the case mix was similar at each place, and most were highly experienced tertiary centers, Damiano told heartwire .

"That variability was almost certainly due to [the surgeons] not performing the procedure correctly--which is shown in the ablation times," he said. Ablation times tracked with success and ranged from less than three minutes, associated with a success rate of 50%, to more than 12 minutes, with a success rate of 81%.

"The thing is, when the ablation time is nine minutes or less, which was over half our patients, you can't do the [Cox-maze IV] lesion set. So even though the surgeons said they were doing the lesion set, they probably weren't."

Dr Niv Ad (Inova Heart and Vascular Institute, Falls Church, VA), the assigned discussant for Damiano's presentation, said, "The variability of the results between centers is probably one of the most important findings in the study, as it raises the question of the role of training."

Damiano agreed. The results "are indicative of the need for more effective procedural and device training. I think when it's performed well, it has a very high cure rate," he said.

"In any surgical treatment of atrial fibrillation, one thing that has impeded progress has been the tremendous variability from center to center. It was very obvious in this trial, where we were all supposed to perform the exact same procedure in the same way" when, Damiano said, "clearly we weren't all performing the same procedure."

In CURE-AF, 150 patients (mean age 70.5 years, 56% male) with no prior history of atrioventricular nodal ablation underwent irrigated unipolar or bipolar RF ablation (Cardioblate, Medtronic) for persistent AF at concomitant cardiac surgery. Operators were assigned to use the Cox-maze IV procedure to achieve pulmonary-vein isolation.

The patients had predominantly one-valve (53%) or two-valve (30%) repair with CABG or CABG without valve surgery (15%). Their mean AF duration was 63.5 months; their LVEF had to be >30%, and 94% were in NYHA class 2 or 3 heart failure.

The composite 30-day event rate, the primary safety end point, was 6.6% and included stroke in 1.3%, pulmonary embolism in 1.3%, and death in 4%. There were no device-related complications, Damiano said.

Whether pulmonary vein isolation was achieved was assessed in 122 patients, or 81% of the total; it was achieved in all 122 cases, which were assessed by 24-hour Holter at six to nine months.

Success of Irrigated RF Ablation at Concomitant Cardiac Surgery (by 24-Hour Holter Monitoring at Six to Nine Months) by Type of Baseline AF

End point Overall, n=122 (%) Persistent AF, n=27 (%) "Longstanding persistent" AF, n=92 (%)*
Freedom from AF (regardless of antiarrhythmic therapy 66 82 63
Freedom from antiarrhythmic therapy 53 67 51

All differences nonsignificant

*Three other patients had paroxysmal AF

Left atrial diameter (mean 5.2 cm) was the only significant predictor of ablation success; it had an odds ratio of 0.55 (95% CI 0.31–0.97; p=0.039), independent of age, sex, duration of AF, total RF ablation time, and number of concomitant procedures.

Although they weren't independently significant predictors of ablation success in this analysis, total RF ablation time and number of concomitant procedures were significant predictors in univariate analysis and might be expected to track with success in practice, according to Damiano.

"That's maybe because as you have more complex cardiac pathology [as, for example, in multiple-valve procedures with CABG], you're also more likely to have significant atrial remodeling. That's an important factor we tend not to measure or take into account. Once you get a lot of atrial fibrosis, the success rate of this procedure falls. It's something that requires further study."

Success Rates for Irrigated RF Ablation of AF at Concomitant Cardiac Surgery by Left Atrial Diameter and by Total RF Ablation Time

Parameter Freedom from AF at 6–9 mo (%)
Left atrial diameter (cm)  
3.0-4.5 69
4.5-6.0 60
>6 36
Total RF ablation time (min)  
<3 50
>3 to <6 50
>6 to <9 63
>9 to <12 71
>12 81


CURE-AF was sponsored by Medtronic. Damiano discloses being a consultant for AtriCure and Medtronic and receiving research and educational grants from AtriCure and Edwards Lifesciences. Ad had no disclosures.


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