The Gap-AF – AFNET 1 trial was conducted by the German Atrial Fibrillation Network (AFNET) under the direction of Prof. Dr. Karl-Heinz Kuck (Hamburg), Prof. Dr. Günter Breithardt (Münster), and Prof. Dr. Stephan Willems (Hamburg) at seven centers in Germany. Its objective was to show in patients with symptomatic paroxysmal atrial fibrillation that a strategy of catheter ablation aiming at complete electrical isolation of the pulmonary veins from the atrial myocardium is superior, in terms of recurrence of atrial fibrillation, to a strategy of catheter ablation that intentionally leaves singular conduction gaps from the pulmonary veins to the atrial myocardium (incomplete pulmonary vein isolation).
A total of 233 patients were enrolled into the trial, with 116 patients allocated incomplete pulmonary vein isolation and 117 patients allocated complete pulmonary vein isolation. The ablation strategy was randomly allocated. After treatment, all patients received a telemetry device for three months and were asked to record an electrocardiogram at least once per day – particularly if they experienced symptoms that were likely related to recurrence of atrial fibrillation – and transmit it for analysis. Patients underwent a repeat electrophysiological study after three months.
The trial demonstrated the superiority of catheter ablation aiming at complete pulmonary vein isolation with high statistical significance. Recurrences of atrial fibrillation were observed in 71 patients who had undergone complete pulmonary vein isolation and 90 patients in whom the pulmonary veins had been incompletely isolated, corresponding to freedom from recurrence of atrial fibrillation of 37.8% and 20.8%, respectively. Thus, there was a difference in freedom from recurrence favoring complete pulmonary vein isolation of 17.1% (95% confidence interval, 5.3% to 28.9%, p < 0.001).
However, during the repeat electrophysiological study at three months, conduction gaps were found in 70% of patients with initially complete pulmonary vein isolation. The authors therefore concluded that the functional endpoint of complete pulmonary vein isolation is not adequate for the successful ablation of atrial fibrillation. Prof. Kuck explains: “In acute pulmonary vein isolation it is impossible to differentiate between cell oedema and necrosis. In the case of an oedema the cell will recover and reconduction will occur! Therefore, the functional endpoint of pulmonary vein isolation needs to be supplanted by a morphological endpoint of lesion assessment with evidence of transmural necrosis.”
Clinical trial registration: NCT00293943 (https://clinicaltrials.gov/ct2/show/NCT00293943)
Kuck KH et al. Impact of complete versus incomplete circumferential lines around the pulmonary veins during catheter ablation of paroxysmal atrial fibrillation: Results from the Gap-AF – AFNET 1 trial. Circ Arrhythm Electrophysiol 2016
The Atrial Fibrillation Network association (AFNET) is an interdisciplinary research network comprising scientists and physicians from hospitals and practices dedicated to improving the management of atrial fibrillation through coordinated research in Germany and Europe. Its main objective is to conduct high quality investigator-initiated clinical trials and registries on a national and international level. The AFNET continues the long-term activities of the network which has been funded by the German Federal Ministry of Research and Education over a decade. Since January 2015, specific projects and infrastructures of the AFNET are funded by the German Centre for Cardiovascular Research (DZHK).
Angelika Leute PhD
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