Likelihood of Atrial Fibrillation Increases with Second Ablation

A new study indicates that left atria enlargement after catheter ablation for paroxysmal atrial fibrillation (AF) increases the risk that the condition will recur after a second ablation.

Researchers enrolled 95 patients who were about to undergo a second ablation procedure and compared the recorded size of each patient’s left atrium before the first ablation with its size before the second procedure. They found significant enlargements in 35 patients and no significant change in the other 60 patients.

After an average follow-up of 29.6 months, paroxysmal AF recurred a second time in 33 of the patients, but it was dramatically more common among those whose left atria had expanded between their first and second ablations. Indeed, the condition recurred a second time in 54.1% of those patients but in just 25.0% of the patients with no left atrium growth (P = 0.017).

After adjusting for age and left atrium (LA) diameter, growth between the first and second ablations was associated with more than double the risk of recurrence (hazard ratio = 2.22, 95% confidence interval: 1.02—4.81, P = 0.043).

“Repeat procedure is often performed in patients with recurrence after AF catheter ablation. However, it is still a problem to accurately identify those who will have a successful outcome after a repeat procedure,” wrote the authors of the study, which appears in Europace.

“To the best of our knowledge, this is the first study demonstrating that the LA structural remodelling presented by LA diameter change between the original and repeat procedure could predict the outcome of repeat procedure.”

The research team, whose members work at Capital Medical University in Beijing and the University of Michigan, looked at several other factors that might increase the risk of a second recurrence, but found no significant relationships.

Sheer AF size, which has been shown by several studies to be a significant risk factor for recurrence after a first ablation, did not affect the outcome of repeat procedures in this study. This finding, however, conflicts with a study by Wojcik et al, which found AF size was a risk factor for recurrence after a second ablation.

“The difference between the two studies might be due to: (i) different study population, more than a half of the patients in Wojcik's study were non-paroxysmal AF; (ii) procedural outcome was not defined after the blanking period in Wojcik's study; (iii) potential different ablation methods,” the authors of the current study wrote.

Those authors later noted several potential limitations to their own study. First among them was the use of LA anterior—posterior diameter as a proxy for LA size. Studies have found only a weak correlation between the 2 measurements, but LA anterior–posterior diameter is generally used, they said, because it is so much easier to measure.

Other limitations included the lack of any long-term follow-up with Holter or loop recorders and the inability of the researchers to speculate on what electrophysiological mechanism might create the association between enlargement and recurrence.

Still, the researchers believe the statistical strength of their findings indicate a significant relationship between growth and recurrence.

If further research confirms their findings might help doctors predict which patients will derive long-term benefit from second ablations and which patients should try alternative therapies.