Pulmonary Vein Isolation vs AV Node Ablation Plus Pacing
Abstract & Commentary
By John P. DiMarco, MD, PhD Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville Dr. DiMarco is a consultant for Novartis, and does research for Medtronic and Guidant.
Source: Khan MN, et al. Pulmonary-vein isolation for atrial fibrillation in patients with heart failure. N Engl J Med. 2008;359:1778-1785.
Khan et al report a multicenter trial comparing pulmonary vein isolation vs AV junctional ablation with biventricular pacing in patients with atrial fibrillation and heart failure. Patients were eligible for the study if they had an ejection fraction of less than 40%, were on appropriate medical therapy, could complete a six-minute walk test, and had class II or III New York Heart Association congestive heart failure. Patients were randomized to either a rhythm control strategy involving pulmonary vein isolation with additional antiarrhythmic therapy, if required, vs AV junctional ablation and biventricular pacing. Pulmonary vein isolation was performed using standard techniques. Additional ablation lesions in the left and right atrium were permitted at Khan et al's discretion. Repeat procedures were permitted if there were recurrent arrhythmias. The primary endpoint of the study was a composite of changes in the ejection fraction, the distance on a six-minute walk test, and the Minnesota Living with Heart Failure score at six months.
Over a 36-month period, 177 patients were screened in eleven centers. Eighty-one patients eventually were randomized. Forty-one were assigned to the pulmonary vein isolation group and 40 were assigned to the AV node ablation with biventricular pacing group. Most patients in both groups had previously received amiodarone in an effort to control their atrial fibrillation. The mean age was 60 ± 8 years, and more than 90% of the entire group was male. Approximately half of the patients had paroxysmal atrial fibrillation; the other half had either persistent or long-standing atrial fibrillation. The heart rate at rest was 81 bpm and the baseline QRS duration was 91 m/sec.
Among the 41 patients in the pulmonary vein isolation group, eight patients required repeat ablation procedures for either recurrent atrial fibrillation or atrial flutter. At six months, 71% of these patients were free from atrial fibrillation and off antiarrhythmic medications. An additional 17% were free of atrial fibrillation while taking an antiarrhythmic drug. Atrial fibrillation continued in the AV junctional ablation and biventricular pacing group, and 30% of the patients converted from a paroxysmal pattern to a persistent pattern. In contrast, recurrent atrial fibrillation in the pulmonary vein isolation group was always paroxysmal in nature. At six months, the ejection fraction had improved from 27 ± 8% to 35 ± 9% in the pulmonary vein isolation group. In the AV junctional ablation group, the ejection fraction was 29 ± 7% at baseline and 28 ± 6% after six months. The pulmonary vein isolation group showed a small change in left atrial diameter (from 4.9 ± 0.5 cm to 4.5 ± 0.4 cm), whereas there was a slight increase in left atrial diameter in the biventricular pacing group. The six-minute walk test distance improved from 269 ± 54 m at baseline to 340 ± 49 m at six months in the pulmonary vein isolation group. A smaller increase was noted in the AV junctional ablation group (281 ± 44 m to 297 ± 36 m). Quality of life also improved more in the pulmonary vein isolation group.
Occasional procedural complications were noted in both groups. In the pulmonary vein isolation group, three patients had groin bleeding, one had a pericardial effusion, and another developed pulmonary edema. Asymptomatic pulmonary vein stenosis was noted in two patients. In the AV junctional ablation with biventricular pacing group, two patients had left ventricular lead dislodgements, two had high left ventricular pacing thresholds, two had pocket hematomas, and one had a pneumothorax.
Khan et al conclude that in patients with atrial fibrillation and congestive heart failure, a strategy involving pulmonary vein isolation is superior to AV junctional ablation and pacing. Patients undergoing pulmonary vein isolation had greater improvements in left ventricular function, functional status, and quality of life.
This paper shows that an intervention that can successfully restore and maintain sinus rhythm in a high proportion of patients can benefit patients with atrial fibrillation and congestive heart failure. However, before we start recommending this approach in all patients with heart failure, we should recognize some limitations to the study.
This was a multicenter study in which patients were recruited at eleven centers with great experience in atrial fibrillation ablation. Despite this, only 81 patients could be recruited over a 3.5-year period. This may have been because patients were reluctant to undergo an irreversible procedure like AV junctional ablation and biventricular pacing; certainly the patients in the trial represent a very select group of patients. The endpoints in the study were changes in ejection fraction, functional status, and quality-of-life score. There were no deaths in either group. Other relevant endpoints, including hospitalization, are not reported. In fact, it might be anticipated that the need for hospitalization would have been higher in the pulmonary vein isolation group because of recurrent atrial fibrillation recurrences in some of the patients. Further studies will be necessary to see if hospitalizations and economic cost would be decreased by more widespread use of ablation procedures. From the data, it is also hard to know whether the patients had effective rate control while in atrial fibrillation. We are only provided data on the resting heart rate, and the data apparently combine values for both patients in sinus rhythm and those in atrial fibrillation. If a patient has controlled resting and exercise ventricular rates during persistent atrial fibrillation and has a normal QRS duration at baseline, why should we expect them to improve with AV junctional ablation and biventricular pacing? The theoretical benefits produced by regularization of the ventricular rate might well be overcome by substituting pacing, even biventricular pacing, for normal ventricular activation. Finally, the group was relatively young, with a mean age of only 60, and almost all the patients were male. Whether the pulmonary vein isolation approach would be as successful in older patients and women remains to be established.