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UNDER-ATP: Adenosine triphosphate-guided pulmonary vein isolation not effective
LONDON — In patients with atrial fibrillation undergoing catheter ablation, adenosine triphosphate-guided pulmonary vein isolation did not improve outcomes compared with standard pulmonary vein isolation, according to the results of the UNDER-ATP trial.
The findings are in contrast to those of the ADVICE trial, published in The Lancet in July, which found that adenosine-guided pulmonary vein isolation was associated with an increase in the rate of arrhythmia-free survival.
Atsushi Kobori, MD, from the division of cardiology at Kobe City General Medical Hospital, Kobe, Japan, told Cardiology Today that while the study populations between the two trials were different — ADVICE was restricted to those with paroxysmal AF and UNDER-ATP was open to those with all kinds of AF — that does not likely explain the difference, because the results in UNDER-ATP were consistent among all types of AF. Rather, he said, the difference is likely related to the methods of the ablation procedures.
Kobori and colleagues randomly assigned patients with AF requiring catheter ablation to receive conventional pulmonary vein isolation (n = 1,007) or catheter ablation with pulmonary vein isolation plus additional adenosine triphosphate (ATP)-guided ablation (n = 1,112). Patients in the second group received 0.4 mg/kg body weight of ATP.
According to the study background, ATP can identify dormant electrical conduction between the left atrium and the pulmonary veins, and additional ablation until the dormant conduction is gone could prevent a recurrence of AF.
The primary outcome was recurrent atrial tachyarrhythmia lasting longer than 30 seconds or requirement of repeat ablation, hospital admission or use of antiarrhythmic drugs at 1 year following a 90-day blanking period after ablation.
In the ATP group, ATP identified dormant conduction in 27.6% of those patients; among that subset, 98.4% had their dormant conduction successfully eliminated after additional ablation, Kobori said at a press conference at the European Society of Cardiology Congress. The results were simultaneously published in the European Heart Journal.
However, there was no difference in the primary outcome between the groups at 1 year after the blanking period (ATP group, 68.7%; control group, 67.1%; adjusted HR = 0.89; 95% CI, 0.74-1.09).
The results were consistent among those with paroxysmal AF (ATP group, 72.8%; control group, 71.4%; adjusted HR = 0.93; 95% CI, 0.72-1.2) and those with persistent or long-lasting AF (ATP group, 60.7%; control group, 57.7%; adjusted HR = 0.86; 95% CI, 0.64-1.17), Kobori said.
Therefore, Kobori told Cardiology Today, “we think that the most likely explanation for the distinct results between [UNDER-ATP and ADVICE] was the differences in the methods of the ablation procedure, which led to a much lower rate of dormant conduction in the UNDER-ATP trial (27.6% in UNDER-ATP vs. 53% in ADVICE). Our [pulmonary vein isolation] strategies can be characterized by longer waiting time and frequent use of supportive devices for creating durable [pulmonary vein isolation] lesions, including irrigation catheters, 3D navigation systems, double circular catheters, and deflectable sheaths, although a contact force-sensing catheter was used in only 2.3% of patients in our trial.”
He added that “when a contact force-sensing catheter or second-generation cryoballoon is optimally used, the rate of dormant conduction would be around 10%, as reported in recent studies. Thus, the clinical impact of an ATP test in the current advanced ablation strategies is becoming much smaller.”
UNDER-ATP was part of a 2x2 factorial randomized controlled trial in which the same population was also assigned antiarrhythmic drugs or placebo and analyzed in the EAST-AF study. Assignment in the EAST-AF trial did not influence the UNDER-ATP results, and vice versa, Kobori said. – by Erik Swain
References:
Kobori A, et al. Hot Line II: Atrial Fibrillation/Pacing. Presented at: European Society of Cardiology Congress 2015; Aug. 29-Sept. 2; London.
Kobori A, et al. Eur Heart J. 2015;doi:10.1093/eurheartj/ehv457.
Disclosure: Kobori reports no relevant financial disclosures.
Editor's note: On Sept. 8, this article was updated to incorporate a new explanation from Kobori on the different results observed in the UNDER-ATP and ADVICE trials.Perspective
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It is quite disappointing that adenosine didn’t show any effect [outcomes]. I would not have anticipated that. A difference between this and the ADVICE study published in The Lancet is that the ADVICE study included only patients with paroxysmal AF, whereas the UNDER-ATP study [included] a mix of [patients with] paroxysmal and persistent [AF]. We know now that for paroxysmal AF, to have the pulmonary veins isolated is extremely important. Whereas in persistent AF, there are also triggers for AF outside the pulmonary veins. The importance of pulmonary vein isolation is much higher in the paroxysmal AF group than in the persistent AF group. That may be why adenosine didn’t show any effect here; the effect may have been diluted.