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Adenosine triphosphate (ATP)-guided pulmonary vein isolation (PVI) in comparison to conventional PVI did not reduce late recurrence atrial fibrillation (AF) at one year, according to the UNDER-ATP trial featured in the Atrial fibrillation/Pacing Hot Line session yesterday. The large-scale multicentre Japanese study was published simultaneously in the European Heart Journal.
Although radiofrequency catheter ablation has been developed as a curative therapy for AF, recurrent atrial tachyarrhythmias are estimated to occur in 30-40% of patients with paroxysmal AF, and 50-70% with persistent or long-lasting AF. Such recurrent atrial tachyarrhythmias are believed to be caused by electrical reconnections between the left atrium and pulmonary veins.
‘Radiofrequency ablation around the pulmonary veins can electrically block the connection but sometimes there are hidden gaps,’ explained Atsushi Kobori, the study presenter from Kobe City Medical Centre General Hospital, Kobe, Japan. ‘ATP is a chemical that can unmask dormant electrical conduction, therefore we used it after PVI to identify these gaps.’
Between November 2011 and March 2014, 2113 patients with paroxysmal, persistent, or long-lasting AF, recruited from 19 cardiovascular centres in Japan, were randomly assigned to either ATP-guided PVI (n = 1112) or conventional PVI (n = 1001), which involved extensive encircling PVI with use of an irrigation catheter.
After ablation, ambulatory ECGs were recorded twice daily for two weeks, with 24-hour ECG monitoring at hospital discharge, six months and one year. The primary endpoint was recurrent atrial tachyarrhythmias lasting for >30 seconds or those requiring repeat ablation, hospital admission, or antiarrhythmic.drugs at one year.
Results show that 68.7% of patients in the ATP-guided PVI group and 67.1% of patients in the conventional PVI group were free of the primary endpoint at one year (HR 0.89; 95% CI 0.74-1.09; P=0.25). The results were consistent across all the prespecified subgroups.
‘We found no significant impact of ATP on reducing late recurrences of AF,’ concluded Kobori. The findings were in direct contrast to three earlier studies demonstrating that ATP- guided PVI was of benefit. There may be several possible explanations for the discrepancy, wrote the authors in the EHJ, noting the fact that earlier studies were all retrospective and thus inherently associated with selection bias, and that comparisons were made with historical controls.
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