AMIO-CAT: Short-Term Amiodarone After AF Ablation Won't Block Late AF

September 08, 2014

BARCELONA, SPAIN — Starting patients on an eight-week course of amiodarone immediately after ablation for atrial fibrillation (AF) won't cut the risk of AF recurrence over the next six months, suggested a small study presented here at the European Society of Cardiology (ESC) 2014 Congress [1]. There was a hint, however, of a lower risk of atrial arrhythmias within three months of ablation in those with a greater AF burden.

Based on the study, "short-term amiodarone should not be standard treatment after [AF] ablation but should be considered in patients with persistent AF, [potentially] to prevent arrhythmia-related hospitalizations and cardioversions within the first three months following ablation," said Dr Stine Darkner (Copenhagen University Hospital, Denmark) at a media briefing. Darkner also formally presented the study, called Amiodarone Treatment after Catheter Ablation for Atrial Fibrillation (AMIO-CAT), later at the ESC sessions and is lead author on its simultaneous publication in the European Heart Journal.

A total of 212 predominantly male patients, half with persistent AF and half with paroxysmal AF, underwent radiofrequency catheter ablation by pulmonary vein isolation. They were randomized in double-blind fashion to amiodarone at 400 mg twice daily or placebo starting the night of the ablation procedure and continuing for eight weeks.

The primary end point, any documented atrial tachyarrhythmia (AT) lasting at least 30 seconds with onset after an initial three-month blanking period, was met by 39% in the amiodarone group and 48% who took placebo (p=0.18).

But the rates of AT-related hospitalizations and of cardioversions during the initial blanking period, both prespecified secondary end points, were significantly reduced in the amiodarone group compared with the placebo group. The effect seemed to be driven by the subgroup of patients that had been treated for persistent AF, the group reported.

Amiodarone vs Placebo Rate Ratio (p) for Events Within 3-Month Blanking Period

End points All patients, RR (p) Paroxysmal AF, RR (p) Persistent AF, RR (p)
AF/AT-related hospitalizations 0.44 (0.006) 0.53 (0.350) 0.39 (0.004)
Cardioversions 0.36 (<0.001) 0.50 (0.286) 0.32 (<0.001)

Serious adverse events occurred in 24% of patients who received amiodarone and 18% in the placebo group (p=0.30). Amiodarone recipients experienced significantly more nonserious side effects—generally those normally associated with the drug, such as GI symptoms, photosensitivity, and abnormal thyroid laboratory markers, the group noted. Quality-of-life measures improved significantly over six months in both groups (p<0.001 for both changes) but didn't differ significantly between the two groups at either eight weeks or six months.

Amiodarone must be given for a few weeks before it reaches adequate myocardial concentrations, observed Dr Paulus Kirchhof (University of Birmingham, UK), who wasn't involved in AMIO-CAT. Given its pharmacokinetics, he noted for heartwire , "you would actually expect to see only a delayed effect, [whereas] all the investigators found was an effect on early cardioversions and hospitalizations in patients with persistent AF."

Kirchhoff said he could give no firm explanation for the trial's findings but proposed that it may be related to AF as a condition that can result from a range of etiologies. "We need to start thinking about atrial fibrillation as different diseases." The current study, he said, is consistent with the idea that some kinds of AF respond to catheter ablation and others that don't may respond to amiodarone.

Different forms of AF can be distinguished in the electrophysiologic laboratory, but AF therapy generally isn't varied according to AF etiology; that, he said, will require "clinically applicable markers" to apply to individual patients.

This work was supported by the Danish Heart Foundation and the Heart Centre Research Committee at Rigshospitalet, Copenhagen. Darkner and the coauthors declared no conflicts of interest.


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