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Yesterday, the first late-breaking trials session of EHRA 2019 revealed some interesting new insights into the treatment of atrial fibrillation (AF).
Considerable effort has been directed towards developing technologies to achieve safe and durable pulmonary vein isolation (PVI) for the treatment of AF.
Two of the most important recent advances are contact-force-guided radiofrequency ablation and second-generation cryoballoon ablation. However, the relative safety and efficacy of these new technologies have not been compared, and the optimal dose for cryoablation has not been determined.
Doctor Jason Andrade (Vancouver General Hospital, Vancouver, Canada) presented late-breaking results from CIRCA-DOSE, the first large multicentre randomised trial exclusively evaluating modern ablation technologies. He explained the methodology: “At eight centres in Canada, 346 patients undergoing an initial PVI procedure for AF were randomised 1:1:1 to contact-force irrigated RF ablation (CF-RF), cryoballoon ablation using 2-minute cryoapplications (CRYO-2) or cryoballoon ablation using standard 4-minute cryoapplications (CRYO-4). All patients underwent loop recorder implantation for arrhythmia monitoring.”
The primary outcome was time to first documented recurrence of symptomatic or asymptomatic AF, atrial flutter or atrial tachycardia between days 91 and 365 post- ablation, or a repeat ablation procedure between days 0 and 365 post-ablation.
Secondary outcomes included arrhythmia burden, repeat ablation procedures and periprocedural safety.
The results showed that, overall, there was no difference between the ablation technologies. One-year freedom from recurrent arrhythmia on continuous rhythm monitoring was 53.9% in the CF-RF group, 52.2% in the CRYO-4 group and 51.7% in the CRYO-2 (p=0.87). Periprocedural complications occurred at a similar frequency among groups, with 2 patients in the CF-RF group (2.6%), 6 patients in the CRYO-4 group (5.2%) and 7 patients in the CRYO-2 group (6.0%) experiencing a serious adverse event (p=0.24). The only significant difference between groups was a longer procedure duration but a lower fluoroscopy time in the CF-RF group.
Dr. Andrade continued, “A major strength of our trial is the rigorous evaluation of arrhythmia outcomes. All patients received an implantable cardiac monitor. While non-invasive intermittent rhythm monitoring remains the most widely utilised method of determining ablation efficacy, it often fails to detect AF recurrence. Moreover, all of the arrhythmia events were independently adjudicated by a committee blinded to treatment allocation. As such, this can be considered one of the most robust evaluations of modern ablation technologies.”
“In this regard, I think there are two key messages to take from the CIRCA-DOSE trial,” he said. “The first is that each of these technologies is very effective at treating AF. Specifically, the median reduction in AF burden on continuous cardiac monitoring was >99%, with the majority of patients having a post-ablation AF burden of 0% over 12 months of monitoring. The second lesson is that a 4-minute freezing duration is not likely necessary. A 2-minute cryoapplication resulted in similar freedom from recurrent atrial tachyarrhythmia and a similar reduction in AF burden, with a significantly lower procedure duration.”
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