Pilot Study Shows Ablation Is Superior to Biventricular Pacing for Treatment of AF in CHF Patients

November 16, 2006

November 16, 2006 (Chicago, IL) – Results from a small pilot study have shown that pulmonary vein isolation with ablation was significantly better than biventricular pacing in the treatment of atrial fibrillation in a cohort of congestive heart failure patients. Investigators showed that curative ablation eliminated the arrhythmia and improved ejection fraction, quality of life, and six-minute-walk distances and suggest the findings support the use of ablation in the treatment of arrhythmia in these sicker patients.

"Atrial fibrillation is an important clinical problem that is extremely prevalent in patients with heart failure," said lead investigator Dr Andrea Natale (Cleveland Clinic, OH). With many refractory to drug treatment, Natale said there is a need to look to new treatment options, such as pulmonary vein isolation with ablation, in the management of these patients.

The results of the study, known as the Pulmonary Vein Antrum Isolation versus AV Node Ablation with Biventricular Pacing for the Treatment of Atrial Fibrillation in Patients with Congestive Heart Failure (PABA-CHF), were presented here today at the American Heart Association 2006 Scientific Sessions.

Commenting on the results of the study, Dr Alan Kadish (Northwestern University Medical School, Chicago, IL) said the study supports the concept that curative atrial fibrillation is effective even in the presence of congestive heart failure, as these sicker patients had better outcomes with rhythm control using state-of-the-art ablation therapy.

"I think the AFFIRM [Atrial Fibrillation Follow-up Investigation of Rhythm Management] principle that rate and rhythm control are equivalent needs reevaluation, because some populations weren't studied in AFFIRM and because rhythm-control techniques have improved," said Kadish. "Despite the small number of patients and limitations, the data from PABA-CHF are compelling enough, I think, to change practice at experienced centers with atrial fibrillation ablation in drug-resistant patients with heart failure. Curative atrial fibrillation ablation seems to a reasonable and preferable alternative to AV node ablation in CRT therapy."

Perception of difficulty

Speaking with heartwire , Natale said that patients with heart failure have typically been difficult to treat with pulmonary vein isolation because of changes in the structure of the heart.

"Patients with congestive heart failure usually have larger left atrial size, and the same way that they develop cardiomyopathy in the bottom chamber, they have some structural changes of the muscle in the upper chamber," he said. "These are patients who are more technically challenging. One reason that other centers have not considered this group for ablation before is that there is a perception that they might be more difficult. It is not true across the board, but in some patients you are dealing with a large upper chamber, large pulmonary veins. Everything is bigger, it requires more ablation, and as a result is more technically challenging."

In the present study, investigators randomized 77 congestive heart failure patients with drug-refractory paroxysmal and chronic atrial fibrillation to AV node ablation with biventricular pacing or pulmonary vein isolation, a technique that included antrum isolation and, based on institutional preference, either linear lesions or the ablation of additional sites based on the characteristics of the left atrium. Patients were approximately 60 years of age, and a majority were male. The duration of atrial fibrillation before treatment was four years. The mean ejection fraction at baseline was 27%.

After six months, 72% of patients were free from atrial fibrillation, and less than 30% of patients had a second ablation procedure. At the discretion of the participating center, if patients were not free from atrial fibrillation after the first procedure, they were then treated with the antiarrhythmic drug they last failed before the ablation procedure. If that drug failed again, a second procedure was attempted. At six months, 90% of patients treated with ablation or antiarrhythmic medication were free of atrial fibrillation.

Regarding the composite primary end point, investigators report significant improvements in quality of life with pulmonary vein isolation and significant improvements in ejection fraction, which increased to 35% among those who underwent pulmonary vein isolation, as well as significant improvements in the six-minute-walk test when compared with those who were treated with AV node ablation and biventricular pacing. Natale said that all patients were treated with anticoagulants for at least three months, although it was recommended clinicians maintain anticoagulation therapy for six months.

Differences between paroxysmal and chronic atrial fibrillation

When investigators compared the effects of pulmonary vein antrum isolation with ablation in those with paroxysmal and chronic atrial fibrillation, they found that patients with chronic atrial fibrillation fared the best, with greater improvements in ejection fraction and changes in left atrial size. Asked if the intervention might be recommended for these patients only, Natale said those with paroxysmal atrial fibrillation also benefit from treatment. In these patients, there was an improvement in quality of life and functional capacity, he said, noting that about a third of patients who receive biventricular devices are rehospitalized because of paroxysmal atrial fibrillation.

Dr Melissa Walton-Shirley (TJ Samson Community Hospital, Glasgow, KY), the moderator of theheart.org forum, told heartwire that the most troubling patients she sees in clinical practice are those with a mild reduction in ejection fraction and end-stage chronic obstructive pulmonary disease. Some of these patients return regularly to the hospital because of atrial fibrillation. Although it is possible that pulmonary vein isolation might be used in the treatment of these patients to eliminate their atrial fibrillation, Natale cautioned that this is not a simple procedure, one of the limitations that might prevent it from taking off in the community. However, he said that such patients are those most likely to benefit from pulmonary vein antrum isolation.

During the scheduled discussion of the PABA-CHF trial, Kadish said the results are impressive given the morbidity of the patients. Like Natale, he cautioned that one of the limitations of the procedure is the difficulty of the ablation technique, which could limit the widespread applicability of the results. Kadish compared the findings from PABA-CHF with the findings from AFFIRM, a study that showed a benefit for rate control, and said the different patient population, as well as the improvement in techniques for maintaining sinus rhythm, were likely responsible for the disparate findings.

In terms of future study, Natale said that the next randomized study will include 200 patients or more, involve more centers, and be designed to analyze the effect of treatment on rehospitalization due to heart failure, with a cost analysis and longer-term follow-up on freedom from atrial fibrillation.

The complete contents of Heartwire , a professional news service of WebMD, can be found at www.theheart.org, a Web site for cardiovascular healthcare professionals.

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