ACCEL | Over the past decade, catheter ablation has emerged as a potential cure for AF, although sometimes the procedure needs to be performed multiple times for long-term effectiveness.

One of the most important questions related to this therapy remains unanswered: does long-term maintenance of SR after successful catheter ablation eliminate stroke risk in patients with AF, thus permitting discontinuation of oral anticoagulation therapy (OAT)?

Without a well-studied answer to that question, two recent expert consensus documents recommend continuing OAT indefinitely, at least in patients at high risk of thromboembolic events (TE).^1,2 Nevertheless, it remains controversial and some centers implement a policy of withdrawing OAT even in the majority of patients at high risk of TE (17% of 42 centers worldwide surveyed in a recent questionnaire).

Best Data to Date, But…

Themistoclakis and colleagues reported an evaluation of 3,355 patient records from five well-known AF ablation centers.³ In 2,692 patients (~80%), OAT was discontinued 3 to 6 months after ablation, although these patients were continued on aspirin therapy (Off-OAT group).

During 2-year follow-up, 0.07% of the Off-OAT group patients and 0.45% of On-OAT patients had an ischemic stroke. A major hemorrhage occurred in one Off-OAT patient and 13 On-OAT patients. In this nonrandomized study, the risk/benefit ratio favored the suspension of OAT after successful AF ablation even in patients with a CHADS2 risk score of ≥2.

No controversy ends easily, so it should be no surprise that there were “issues” with the authors’ conclusion. In an accompanying editorial comment, Ivan Cakulev, MD, and Albert L. Waldo, MD, FACC , both of Case Western Reserve University and Medical Center, Cleveland, OH, wrote they believe strongly that it is premature to accept the conclusion by Themistoclakis et al.

They noted that the authors reported a very low incidence of thromboembolism in the Off-OAT group. However, the incidence of stroke was strikingly low in the On-OAT group as well. Warfarin reduces but does not eliminate the risk of stroke in patients with AF. Even in the patients with a CHADS2 score of 0, the expected annual incidence of stroke should be significantly higher than the overall incidence of 0.23% reported in this study. (On the other hand, the reported incidence of major hemorrhagic episodes in the OAT group does match the expected incidence reported in the literature.)

Also, only 347 (13%) of the patients in the Off-OAT group had a CHADS2 score >2, and only 10 patients had a CHADS2 score of 5 to 6. Cakulev and Waldo noted that current guidelines suggest warfarin therapy in patients with AF and a CHADS2 scores of >2. “To change this practice on the basis of data from such a small subgroup in a nonrandomized, observational study seems unwise.”

Now What?

For now, they suggest following the U.S. and European consensus statement⁴:

• Warfarin is recommended for all patients for at least 2 months after an AF ablation procedure.
• Decisions regarding the use of warfarin more than 2 months after ablation should be based on the patient’s risk factors for stroke and not on the presence or type of AF.
• Discontinuation of warfarin therapy post-ablation is generally not recommended in patients who have a CHADS2 score >2.
• In short, Cakulev and Waldo said the study by Themistoclakis is really only hypothesis generating. They wrote: “These data cry out for a prospective, randomized clinical trial that includes standardized methods of follow-up to assess and characterize recurrence of atrial fibrillation and to determine the incidence/prevalence of stroke.”

References

1. Natale A, Raviele A, Arentz T, et al. Electrophysiol. 2007;18:560-80.
2. Calkins H, Brugada J, Packer DL, et al. Heart Rhythm. 2007;4:816-61.
3. Themistoclakis S, Corrado A, Marchlinski FE, et al. J Am Coll Cardiol. 2010; 55:735-43.
4. Cakulev I, Waldo AL. J Am Coll Cardiol. 2010;55:744-6.

Keywords: CardioSource WorldNews, Atrial Fibrillation, Avena, Catheter Ablation, Health Services

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