Complete linear lesions when using catether ablation to isolate pulmonary veins have shown to be more effective than incomplete lesions in preventing recurrence of atrial fibrillation, according to results from the GAP-AF study presented by Karl-Heinz Kuck at a late-breaking trial session of the European Heart Rhythm Association (EHRA) Europace meeting (23–26 June, Athens, Greece).
According to Kuck, this is the first time that a randomised controlled study has been undertaken comparing the two different ablation strategies for patients with paroxysmal atrial fibrillation.
The Heart Rhythm Society/European Heart Rhythm Association/European Society of Cardiology Expert Consensus Document on Catheter and Surgical Ablation of Atrial Fibrillation (published in 2007 and updated in 2012) states that patients undergoing catheter ablation for atrial fibrillation should have complete isolation of the pulmonary veins, which involves a complete circumferential lesion being created around the pulmonary vein.
“This recommendation was based on observational studies, not on a prospective randomised trial. But some electrophysiologists continue to believe that it is sufficient to create incomplete linear lesions where conduction sites still exist between the pulmonary veins and left atrium,” said Kuck, Asklepios Klinik St George, Hamburg, Germany.
Part of their reasoning is that 95% of patients with atrial fibrillation recurrence after complete pulmonary vein isolation procedures are found to have conduction gaps between the pulmonary veins and the left atrium, he said. “Since they cannot isolate the pulmonary veins permanently, they reason that incomplete isolation is sufficient and has the advantage of being a shorter procedure, with a potentially lower complication rate and lower costs,” said Kuck.
GAP-AF is a prospective, randomised, adaptive, multicentre study that enrolled 233 patients with drug refractory paroxysmal atrial fibrillation between February 2006 and August 2010. The patients were randomised to have either a complete procedure (n=117) or an incomplete procedure (n=116). For the incomplete procedure the electrophysiologists stopped the radiofrequency application at one site to permit reconduction from the circumference. The groups are being compared over a follow-up of 12 months.
Kuck commented that in order to further assess the development of the pulmonary vein isolation, all patients will undergo an invasive re-evaluation of pulmonary vein conduction three months after the ablation procedure.
The study, which was performed in seven German centres, was funded by the German Atrial Fibrillation Network (AFNET). The inclusion criteria for the study were that patients had to be aged over 55 years and have been treated with one antiarrhythmic drug before they entered the trial. Patients with poor left ventricular function were excluded from the study.
The primary endpoint of the study was the time to first recurrence of symptomatic atrial fibrillation with duration of more than 30 seconds on transtelephonic ECG monitoring, or detection of asymptomatic atrial fibrillation defined as two consecutive recordings of atrial fibrillation during a minimum of 72 hours.
Results showed that at the three-month follow-up, sinus rhythm had been achieved in 38.8% (46) of patients who had complete ablation, versus 20.8% (26) with incomplete ablation (p<0.001). Furthermore, the mean number of days in sinus rhythm was 60 days for the complete group versus 16 days for the incomplete group (p<0.001).
At three months, when patients were taken back to the electrophysiology lab for a repeat investigation, 70% of those randomised to complete pulmonary vein isolation had gaps versus 89% randomised to incomplete pulmonary vein isolation.
No statistically significant differences were found for serious adverse events (including syncope, stroke, major bleeding, tamponade) between the two groups.
“The study shows us for the first time that complete isolation of the pulmonary veins is more effective than incomplete isolation. It suggests that the level of evidence for complete ablation should be upgraded from class Ic to class Ia, where it is supported by a multicentre randomised trial,” said Kuck.
However, the study also highlighted that recurrence rates were high even for patients who had undergone complete isolation procedures. “Research is urgently needed to improve ablation techniques to make the complete lines more durable. There is a need to explore other energy sources and tools for catheter ablation,” he said.