Early Atrial Fibrillation Clinical Trial: Superiority of Catheter Cryoablation Over Antiarrhythmic Therapy as First Line Therapy for Paroxysmal Atrial Fibrillation

Sara Zand, M.D.
By Sara Zand, M.D. on

A recent study by Dr. Jason G. Andrade, published in New England Journal of Medicine, found that the use of catheter cryoablation as first-line therapy for patients with newly diagnosed, symptomatic, paroxysmal atrial fibrillation is associated with lower recurrence of arrhythmia and a better quality of life when compared to an antiarrhythmic treatment approach.

Atrial fibrillation is the most common tachyarrhythmia, with a high incidence and no preventive treatment strategies. The current guidelines recommended antiarrhythmic drugs as the initial therapy for paroxysmal atrial fibrillation. If medical therapy fails to maintain sinus rhythm, cryoablation therapy is recommended. However, catheter ablation can be an initial treatment and is thought to be more effective in the prevention of tachyarrhythmia recurrence, resulting in an improvement in the quality of life.

Dr. Andrade and his colleagues conducted a multicenter, open-label, randomized trial with blinded endpoint adjudication between January 17, 2017, and December 21, 2018, at 18 centers in Canada. They randomly enrolled 303 patients with symptomatic, paroxysmal, untreated atrial fibrillation to undergo catheter ablation with a cryotherapy balloon or to receive antiarrhythmic drug therapy for initial rhythm control. Patients were excluded from enrollment if they had a history of daily use of class I or class III antiarrhythmic drugs at therapeutic doses. Patients were included in the trial if they met the following criteria: a history of using antiarrhythmic drugs for more than the past 6 months or a history of treatment with class I or III antiarrhythmic drugs within the past 6 months below the therapeutic threshold (<100 mg per day for flecainide, <300 mg per day for propafenone, <160 mg per day for sotalol, and <800 mg per day for dronedarone), or temporarily (at a therapeutic dose for <4 weeks). Implantable cardiac monitoring was inserted for all patients less than 24 hours after initiating antiarrhythmic therapy or cryoablation. For patients assigned to medical therapy, antiarrhythmic drugs were initiated within one week of group assignment.  For patients assigned to cryoablation therapy, pulmonary-vein isolation was performed. Patients were followed for 1 year with regular visits, telephone calls for the analysis of cardiac rhythm recorded by implantable cardiac monitoring. The primary endpoint was defined as the recurrence of every atrial tachycardia between 91-365 days of initiating antiarrhythmic therapy or catheter ablation. The secondary endpoints included the first recurrence of symptomatic tachyarrhythmia, the burden of tachyarrhythmia, quality of life, and serious adverse effects.

The results of the study at 1 year demonstrated that atrial tachyarrhythmia occurred in 66 of the 154 patients assigned to the cryoablation group (42.9%) and in 101 of the 149 patients assigned to the antiarrhythmic therapy group (67.8%) (hazard ratio (HR): 0.48; 95% confidence interval (CI):0.35 to 0.66; P<0.001). Symptomatic atrial tachyarrhythmia recurred in 17 of the 154 patients who received ablation, as compared with 39 of the 149 patients who received antiarrhythmic drugs (HR: 0.39; 95% CI: 0.22 to 0.68).

 It is important to consider the study limitations. Namely, the impact of reduced atrial fibrillation recurrence on cardiovascular outcomes is unclear. In addition, the study’s finding cannot be generalized to other types of ablation energy sources such as radiofrequency and microwave ablation as it only assessed the cryoablation therapy as compared with medication therapy.

According to this trial, the occurrence of atrial fibrillation was significantly reduced when cryoablation was used as the first-line therapy as compared with antiarrhythmic therapy among patients with paroxysmal atrial fibrillation.  These findings warrant further research.

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