Catheter Ablation for Paroxysmal Atrial Fibrillation

Abstract & Commentary

Synopsis: In patients without structural heart disease and normal left atrial size, left atrial ablation provides a higher success rate than segmental pulmonary vein ostial ablation.

Source: Oral H, et al. Circulation. 2003;108:2355-2360.

In this paper, Oral and colleagues compared 2 current ablation techniques in patients with paroxysmal atrial fibrillation. Eighty patients with paroxysmal atrial fibrillation were randomized to undergo pulmonary vein isolation either by segmental ostial ablation or by left atrial ablation. The segmental ostial ablation technique requires 2 transseptal catheters. A multipole lasso catheter is placed in the ostia of each of the pulmonary veins. Circumferential lesions are then placed with a second catheter to electrically isolate each vein. This is assessed during the case by looking for the disappearance of pulmonary vein potentials during atrial pacing. The left atrial ablation technique used an 8 mm tipped catheter to construct an electroanatomic map of the left atrium. Circular lesions were placed around the left and right pulmonary veins using the electroanatomic data for catheter positioning. The circumferential lines were connected with an ablation line along the posterior left atrium. Finally, ablation was performed along the mitral isthmus between the inferior portion of the left-sided encircling lesion and the lateral mitral annulus. After the ablation procedure, patients were followed for recurrent paroxysmal atrial fibrillation. Occurrences during the first 2-4 weeks were not included in the analysis.

There were 40 patients in each group. The mean age was 51 ± 10 for the segmental ablation group and 54 ± 11 for the left atrial ablation group. Both groups had 31 men and 9 women. Only 3 patients in the segmental ablation group and 1 patient in the left atrial ablation group had structural heart disease.

All pulmonary veins in each of the patients in the segmental ablation group were successfully isolated. The total duration of radiofrequency applications needed to isolate the veins was 18 ± 9 minutes per patient. The total duration of the procedure was 156 ± 45 minutes. In the left atrial ablation group, the mean total duration of radiofrequency energy applications was 42 ± 14 minutes with a total procedure time of 149 ± 33 minutes. Although the duration of energy application was longer in the atrial ablation group, the total procedure time was not increased since electrical measurements were not required. The mean total fluoroscopy times were 50 ± 17 minutes for segmental ostial ablation compared with 39 ± 12 minutes for left atrial ablation (P = .06).

After the first ablation procedure, atrial fibrillation recurred in 13 of 40 patients (32%) who underwent segmental ostial ablation and in 4 of the 40 (8%) patients who underwent left atrial ablation. Life-table analysis showed that at 6 months of follow-up, 67% of patients who underwent segmental ostial ablation were free of recurrent paroxysmal atrial fibrillation compared with 88% of patients who underwent left atrial ablation. (P = .02).

A repeat ablation procedure was performed in 7 patients in the segmental ostial ablation group. Recovery of conduction in one or more pulmonary veins was seen in all of these patients. Repeat isolation was carried out, and these patients subsequently remained free of recurrent atrial fibrillation. One patient in the left atrial ablation group developed left atrial flutter and required a repeat procedure.

Oral et al conclude that in patients without structural heart disease and normal left atrial size, left atrial ablation provides a higher success rate than segmental left atrial ablation.

Comment by John DiMarco, MD, PhD

Techniques for catheter ablation in patients with paroxysmal atrial fibrillation are still rapidly changing. The initial proposal by Haissaguerre and colleagues1 recommended identification of triggers for atrial fibrillation in one or more pulmonary veins or other atrial sites and isolation of only the veins or sites that produced triggers. It was soon found that triggers were difficult and tedious to reproduce at the time of study, and most centers now try to isolate all pulmonary veins in the majority of patients. Assessing electrical isolation is technically difficult during an ablation since 2 catheters in the left atrium are required. To overcome these problems, Pappone and colleagues2 have proposed an anatomically based approach, which draws large circles around the pulmonary veins using electroanatomical mapping. Electrophysiologic testing during the procedure is not routinely performed. Placement of the lesions is guided by the electroanatomic mapping, not by electrophysiologic findings. The proposed advantages of the latter technique are that it requires only a single transseptal catheter and that it places lesions far from the orifice of the pulmonary veins, therefore minimizing the risk for late pulmonary vein stenosis.

This paper by Oral et al shows that in a large, experienced center, left atrial ablation, as a single procedure, seems to be more effective than segmental pulmonary vein ostial ablation. It should be noted, however, that the patients in this study were relatively young and for the most part had either normal left atrial size or only mild left atrial enlargement. The real challenge in patients with atrial fibrillation is whether the current ablation techniques can be extended to patients with a history of structural heart disease and/or left atrial enlargement. These patients form, by far, the largest group of patients with atrial fibrillation, and they are the ones in whom ablation has been the least successful.

Dr. DiMarco, Professor of Medicine, Division of Cardiology, University of Virginia, Charlottesville, is on the Editorial Board of Clinical Cardiology Alert.

References

1. Haissaguerre M, et al. N Engl J Med. 1998;339: 659-666.

2. Pappone C, et al. J Am Coll Cardiol. 2003;42:185-197.