BARCELONA – Eight weeks of oral amiodarone beginning right after catheter ablation for atrial fibrillation more than halved the rates of cardioversion and arrhythmia-related hospitalization for 3 months in the AMIO-CAT trial.
This was a consequence of the sharp reduction in the incidence of AF lasting more than 30 seconds during that interval: 34% in the amiodarone group, compared with 53% in placebo-treated controls, Dr. Stine Darkner reported at the annual congress of the European Society of Cardiology.
Dr. Stine Darkner
“Patients undergoing catheter ablation for AF quite often experience arrhythmias within the first few months after ablation. The ablation itself is thought to cause some of these arrhythmias. It is quite a distressing experience for the patient,” observed Dr. Darkner of Copenhagen University Hospital.
While the benefits at 3 months were significant for the study population as a whole, upon closer analysis the benefits reached statistical significance only in patients treated for persistent AF. Although trends were favorable in subjects with paroxysmal AF, the benefits were less pronounced.
“The implication is that short-term amiodarone should perhaps not be standard treatment after ablation, but should be considered in patients with persistent AF,” she concluded.
At 6 months, there was no significant difference in the cumulative AF recurrence rate, which was the prespecified primary outcome. The rates were 52% in the amiodarone group and 61% with placebo, according to Dr. Darkner.
AMIO-CAT (Amiodarone After Catheter Ablation for Atrial Fibrillation) was the first double-blind, placebo-controlled clinical trial to evaluate the impact of a short course of amiodarone on recovery after AF ablation. The study comprised 212 patients undergoing radiofrequency ablation for paroxysmal or persistent AF.
During the first 3 months post ablation, a time that electrophysiologists call “the blanking period,” the amiodarone group experienced a 57% lower risk of atrial tachyarrythmia-related hospitalization and a 64% reduction in cardioversions, compared with controls.
The side effects reported by patients on amiodarone were transient and are familiar in nature to physicians who prescribe the antiarrhythmic agent: sleep disruption, GI complaints, photosensitivity, and asymptomatic changes in thyroid hormone levels. None of the side effects was serious. Quality of life as measured by the SF-36 was not reduced in the amiodarone group, despite the increase in side effects.
The dosing regimen in the study was amiodarone at 400 mg on the night of the ablation, then 400 mg twice daily for 13 days, followed by amiodarone at 200 mg twice daily for 2 weeks, and finally 200 mg once daily for 4 weeks.
Discussant Karl-Heinz Kuck said he wasn’t surprised by the lack of benefit at 6 months in AMIO-CAT.
“We know that in patients with paroxysmal or persistent AF, the predominant cause of atrial arrhythmia recurrence post ablation at any point in time is pulmonary vein reconduction, which is unlikely to be altered by 8 weeks of amiodarone, especially after discontinuing the drug. We know that AF begets AF, but we don’t know that sinus rhythm begets sinus rhythm,” said Dr. Kuck, head of cardiology at St. Georg Hospital in Hamburg, Germany.
A more promising strategy to reduce the long-term AF recurrence risk is to create more durable lesions for pulmonary vein isolation, he added.
Another discussant, Dr. Paulus Kirchhof, took an upbeat view of AMIO-CAT.
“My take is that your secondary outcome – reduced hospitalizations – may actually have greater impact for the patient, for patient care, and for payers, than the primary outcome of arrhythmia recurrence,” said Dr. Kirchhof, professor of cardiovascular sciences at the University of Birmingham (England).
Dr. Darkner noted that while she and her coworkers didn’t carry out an economic analysis, it’s quite likely that the reduction in hospitalization and cardioversions would translate into decreased cost of postablation care.
Simultaneously with her presentation in Barcelona, the AMIO-CAT results were published online (Eur. Heart J. 2014 PMID: 25182250).
AMIO-CAT was funded by the Danish Heart Foundation and the Heart Center Research Committee at Copenhagen University Hospital. Dr. Darkner reported having no financial conflicts. Dr. Kirchhof and Dr. Kuck disclosed receiving research grants from and/or serving as consultant to numerous medical device and pharmaceutical companies.