In ablation for persistent atrial fibrillation, 'less may be more'

In patients with persistent atrial fibrillation (AF) - an abnormal heart rhythm – treating only the pulmonary veins with a procedure called ablation resulted in reasonable outcomes without the need to treat other areas of the heart, according to a new study presented as a Hot Line today at ESC Congress 2014.

"Addition of further ablation increased treatment time but did not reduce the recurrence of AF," said Atul Verma, MD, a cardiologist from Southlake Regional Health Centre, in Newmarket, Canada, and principal investigator of the Substrate and Trigger Ablation for Reduction of Atrial Fibrillation Part 2 (STAR AF 2) trial.

STAR AF 2, was conducted in 12 countries, and is the largest randomised trial to examine outcomes of ablation in persistent AF.

"The results of this trial will likely change practice by shifting the focus to shorter and more effective pulmonary vein ablation alone without the addition of other ablation," he said. "Our results have important implications for procedural safety and duration. Experts will need to reconsider current ablation guidelines to reflect these findings in patients with persistent AF."

During ablation, catheters inserted into the heart deliver radiofrequency energy to destroy areas that trigger rhythm abnormalities. Despite limited data on the outcomes of ablation in persistent AF, current guidelines recommend more extensive ablation beyond just the pulmonary veins alone, explained Dr. Verma.

STAR AF 2 was designed to explore the optimal method and outcomes of ablation in persistent AF.

A total of 589 patients with persistent AF were randomised to receive either pulmonary vein ablation alone (PVA; n=67); PVA plus ablation of atrial regions of the heart that produce abnormal electrograms (PVA+electrograms; n=263); or PVA plus ablation of linear lesions in the left atrium (PVA+lines; n=259).

Most patients (76%) had been experiencing continuous atrial fibrillation for at least 6 months before their treatment (median duration 2.2 years).

Successful pulmonary vein ablation was achieved in 97% of all patients with no differences between groups, however, procedural time was significantly shorter for the PVA alone group (167 mins) compared to the PVA+electrograms and PVA+lines groups (229 and 223 mins respectively; p<0.001).

At 18 months, freedom from the primary outcome of the trial, which was AF recurrence either with or without anti-arrhythmic medication, was not significantly different between the three arms (59% for PVA alone, 48% for PVA+electrograms, and 44% for PVA+lines; p=0.15)

There was also no difference between groups for the number of patients who were free from AF recurrence without anti-arrhythmic medication (PVA alone 48%; isolation+electrograms 37%; and isolation+lines 33%; p=0.11).

Similarly, after two ablation procedures, freedom from AF recurrence with or without antiarrhythmic medication was also not significantly different between groups (72% for PVA alone, 60% for PVA+electrograms, and 58% for PVA+lines; p=0.18).

"Our data suggest that ablation of the pulmonary veins alone can achieve a successful outcome in about half of patients," said Dr. Verma. "Despite guidelines suggesting additional ablation, our study shows this does not improve outcome. In fact, the results did not change after two ablations, suggesting that even repeated attempts to eliminate non-pulmonary vein targets do not increase success."

There were no significant differences in adverse events between groups, but Dr. Verma noted that "performing additional, and perhaps unnecessary, ablation also has the potential to increase risk. Procedural time in this study was longer by almost an hour in the additional ablation groups and was associated with increased fluoroscopy exposure for patient and operator. While the overall rate of serious adverse events in this trial, such as tamponade or stroke, was very low and is amongst the lowest reported of any multicenter trial to date, it is still noteworthy that one atrial esophageal fistula leading to death occurred in a patient who received additional electrogram ablation."

He concluded that "perhaps instead of additional ablation, we should be considering additional risk factor modification. The take home message is that PVA alone works for persistent AF, and that in terms of ablation, less may be more".