GAP-AF study helps to define optimal approach to ablation

(Press-News.org) Athens, Greece. Tuesday 25 June 2013: Using catheter ablation to create complete linear lesions around pulmonary veins, proved more effective than the creation of incomplete lesions in preventing recurrence of atrial fibrillation (AF), reports the GAP-AF study. The study, presented today in the Late Breaking Clinical Trials session I at the EHRA EUROPACE 2013 meeting in Athens, Greece, represents the first time that a randomized controlled study has been undertaken comparing the two different ablation strategies for patients with paroxysmal AF.

Identification of triggers initiating AF within the pulmonary veins led to prevention of AF recurrence by catheter ablation at the site of origin of the trigger. 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 AF 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 randomized trial. But some electrophysiologists (EPs) continue to believe that it's sufficient to create incomplete linear lesions where conduction sites still exist between the pulmonary veins and left atrium," explained Professor Karl Kuck, from Asklepios Klinik St George, Hamburg ,Germany, presenter of the GAP-AF study.

Part of their reasoning is that 95% of patients with AF recurrence after complete PV isolation procedures are found to have conduction gaps between the pulmonary veins and left atrium, he said. "Since they can't isolate the pulmonary veins permanently, they reason that incomplete isolation is sufficient and has the advantage of being a shorter procedure that has a potentially lower complication rate and costs less," said Prof Kuck.

In the GAP-AF (AFNET1) study between February 2006 and August 2010, 233 patients with drug refractory paroxysmal AF were randomized to have either a complete procedure (n=117) or an incomplete procedure (n=116). For the incomplete procedure the EPs stopped the radiofrequency application at one site to permit reconduction from the circumference. 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 to have been treated with one anti arrhythmic 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 AF with duration of more than 30 seconds on trans-telephonic ECG monitoring, or detection of asymptomatic AF defined as two consecutive recordings of AF during a minimum of 72 hours. The study made use of the RhythmCard™ technology, a small credit card sized device that patients can place on their chest wall to record an ECG whenever they experienced symptoms of AF and transmit the data via the telephone. Additionally, patients were asked to record and transmit an ECG every day regardless of their symptoms.

Results showed that at the three month follow-up, sinus rhythm (normal beating of the heart) had been achieved in 37.8% (46)of patients who had complete ablation, versus 20.8% (26) with incomplete ablation (P12 hours) AF at 12 months (the primary end-point) was 70.4% in the CA group versus 43.7% in the ADT group (p=0.002); implying an absolute risk difference of 26.6% (95% CI: 10.0-43.3) favouring ablation group.

The proportion of patients free of any recurrence of AF or flutter (lasting >30 seconds) was 60.2% in the CA group compared to 29.2% in the ADT group (p END