AF Cryoablation Foregoes Vein Mapping With Good Outcomes

Daniel M. Keller, PhD

March 19, 2019

LISBON — In a trial of a bare-bones approach to cryoablation for the treatment of atrial fibrillation (AF), foregoing intracardiac electrophysiologic (EP) mapping was just as good as conventional cryoablation with pulmonary vein (PV) mapping, suggesting that it is possible to simplify the procedure without compromising outcomes.

In addition, the simplified procedure was superior to therapy with antiarrhythmic drugs during a 1-year follow-up.

Prapa Kanagaratnam, MB BChir, PhD, a consultant cardiologist at Imperial College Healthcare NHS Trust, London, presented the results of the Ablation Verses Anti-arrhythmic Therapy for Reducing All Hospital Episodes From Recurrent Atrial Fibrillation (AVATAR-AF) trial here at the European Heart Rhythm Association (EHRA) 2019 Congress during a late-breaking trials session.

He said with an increasing prevalence of AF, predicted to keep growing, there will be increasing demand for AF ablation, which could be facilitated by techniques requiring fewer resources and lower costs.

Advanced cryoballoons can isolate 85% to 95% of veins on the first cryo application, pointing to the possibility that PV mapping may not be required. If so, there would be no need for specialist recording equipment or electrophysiologists, thereby allowing any catheterization laboratory to do it.

Patients in the AVATAR-AF trial were randomly assigned to one of three groups: an AVATAR protocol of AF ablation without PV mapping (AVATAR group); a medical therapy group (medical group); and conventional cryoablation using mapping (conventional group). The groups were well balanced, with mean age about 60 years, 57% to 66% male, CHA2DS2VASC scores largely in the 0 to 3 range, and mean left ventricular ejection fraction of 57% to 58%.

At study enrollment, about two-thirds of patients in each group were on a single medication for symptom control, 15% to 20% were on two drugs, and the rest were on none. About 40% were taking a class I/III anti-arrhythmic agent. About 63% to 74% were on an anticoagulant (11% to 20% warfarin and the rest on a nonvitamin K oral anticoagulant).

The AVATAR protocol consisted of anticoagulation according to guidelines using the CHA2DS2VASC score, sedation or general anesthesia, transeptal puncture by a catheter, and balloon occlusion of the PV with two 3-minute cryoblations. There was phrenic nerve monitoring using a temporary transvenous pacing wire but no specialist EP catheters or formal assessment of PV isolation.

Men and women 18 to 80 years of age with documented paroxysmal AF who needed modification or initiation of antiarrhythmic drugs for symptom control and who were suitable candidates for catheter ablation were eligible for the trial.

AVATAR group patients (n = 110) initially received day-case cryoablation without PV mapping. Over 12 weeks, if AF symptoms occurred, ablation with any method of mapping was done. In the conventional group (n = 108), standard cryoablation with PV mapping and isolation was achieved by any method. Medical group patients (n = 103) had repeat reviews of medications.

At 12 weeks, patients were discharged from hospital-based specialist care if they were asymptomatic or had improving symptoms. Discharged patients were followed at 6, 9, and 12 months by telephone consultation with a nurse blinded to the treatment group. All groups had at least a 92% completion rate.

At week 12 discharge, the number of AVATAR group patients on a class I/III antiarrhythmic agent dropped by about two-thirds compared with the time of randomization, whereas roughly half of the conventional group patients were off these drugs. The number of patients on these drugs in the medication group doubled.

Use of Class I/III Antiarrhythmic Agents at Randomization and Discharge
Group n %
AVATAR group    
At randomization (n = 110) 42 38.2
At discharge (n = 105) 14 12.7
Medication group    
At randomization (n = 103) 38 36.9
At discharge (n = 92) 78 75.7
Conventional group    
At randomization (n = 108) 39 36.1
At discharge (n = 103) 18 16.7

The AVATAR protocol proved superior to antiarrhythmic therapy in terms of hospital episodes related to treatment for atrial arrhythmia by 1 year, the primary end point of the trial.

"There was a very significant difference," Kanagaratnam said, with "23 events in that arm compared to the anti-arrhythmic group, in which there were 76 events" (P < .001).

"We did not demonstrate superiority with the conventional cryoablation approach," he said. The 23 hospital episodes in the AVATAR group was not significantly different from the 19 events with conventional cryoablation (= .606).

"I think the AVATAR-AF study has shown that the AVATAR protocol is superior to antiarrhythmic agents in avoiding needs for hospital-based tests," he concluded. Furthermore, given the noninferiority of the AVATAR protocol to conventional cryoablation, "we believe it is possible to simplify AF ablation procedures without compromising outcomes."

The study also suggested that long-term follow-up of patients after ablation may not be necessary, just relying on patients to contact the hospital if they are experiencing symptoms. "The findings also question the value of drug therapy and whether catheter ablation should be the first line treatment for atrial fibrillation patients with symptoms," Kanagaratnam proposed.

Jose L. Merino, MD, PhD, La Paz University Hospital, Madrid, provided discussion of the study results and their implications. He asked whether there were differences in the procedure time between the two ablation groups or in the cryo applications between them. He also wondered about the number of re-dos needed, as well as how many crossovers to conventional ablation with mapping of any sort occurred because of symptom recurrences.

He said the implication is that if mapping can be avoided, then any catheterization laboratory could do cryoablation, there would be no need for EP recording equipment, no need for specialist technicians or electrophysiologists, and hence PV ablations for recurrent AF would be largely in the hands of interventionists.

Referring to a point that Merino raised in his discussion, session comoderator Hein Heidbuchel, MD, PhD, president of the EHRA and chair of cardiology at Antwerp University, Belgium, commented to theheart.org | Medscape Cardiology that it was an intriguing finding that the outcomes were similar for the two different ablation scenarios even though the AVATAR protocol did not involve fine isolation of the veins and verification.

"That may have to do, of course, with the clinical end point of the trial because the evaluation for the end point was whether the patient came back to the hospital with symptomatic palpitations. So that can explain part of it, but it remains a little bit of an unexpected finding," he said.

Heidbuchel noted that interventionists are "all struggling to find easier ways to isolate the pulmonary veins." But he said that he does not think that AVATAR-AF "really will be the ground breaking trial facilitating that.... I think that in the minds of electrophysiologists still lives the conviction that we have to evaluate a procedural end point, which is isolation of the vein because that is what we need to have a good clinical outcome."

He also questioned how much time the AVATAR-AF protocol saves, saying that the really time-consuming aspect of the procedure is in the whole set up, getting the catheter to the left atrium, and then isolating the veins, all technically challenging steps regardless of the technology being used.

"That is where we look for breakthroughs. I don't think that the solution is in cutting corners in evaluation of the end point," he said.

The study was funded in part by Medtronic. Kanagaratnam reported consulting relationships with Medtronic, Abbott, and Biosense-Webster, from which he also received royalties. Merino disclosed research contracts with Abbott and Boston Scientific, and consulting, royalties, ownership, or stock in Abbott, Boston Scientific, Microport, and Biosense. As president of EHRA, Heidbuchel has decided not to accept any personal honoraria for any industry-related activity, hence no disclosures.

European Heart Rhythm Association (EHRA) 2019 Congress. Presented March 17, 2019.

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