Who Needs Antithrombotic Therapy After Atrial Fibrillation Ablation?

By Michael H. Crawford, MD

Synopsis: An international trial of rivaroxaban vs. low-dose aspirin started one year or more after successful atrial fibrillation catheter ablation has shown no significant differences in a composite outcome of stroke, systemic embolism, or covert cerebral emboli determined by head magnetic resonance imaging and no differences in major bleeding but shows an increase in clinically relevant minor bleeding with rivaroxaban.

Source: Verma A, Birnie DH, Jiang C, et al. Antithrombotic therapy after successful catheter ablation for atrial fibrillation. N Eng J Med. 2025; Nov 8. doi: 10.1056/NEJMoa2509688. [Online ahead of print].

Current guidelines use the CHA₂DS₂-VASc score rather than the success of atrial fibrillation (AF) ablation to determine the need for oral anticoagulation (OAC) after AF ablation. However, it is unknown whether the elimination of AF decreases the risk of stroke enough to forgo OAC. Thus, the Optimal Anticoagulation for Enhanced Risk Patients Post-Catheter Ablation for AF (OCEAN) trial is of interest.

OCEAN was a prospective, open-label, blinded outcomes randomized trial conducted in 56 sites in six countries. An independent data safety and monitoring board managed the trial. Patients enrolled were one year or more post-successful AF ablation with no AF episodes > 30 seconds on two 24-hour Holter monitoring periods during the year post-ablation and one 48-hour Holter within two months of enrollment. Also, patients had to have a CHA₂DS₂-VASc score of ≥ 1 for men and ≥ 2 for women. Excluded were patients > 80 years of age and patients with chronic kidney disease, valve disease, or disabling stroke within one year or any stroke ≤ 14 days prior to enrollment. In addition, the patients could not have contraindications to OAC, aspirin, or magnetic resonance imaging (MRI).

Enrolled patients were randomized to 70 mg/day to 120 mg/day of aspirin (depending on available strengths in each country) or rivaroxaban 15 mg/day. Follow-up visits were performed at six and 12 months and yearly thereafter. Head MRI was performed at baseline and after three years of follow-up. The primary composite endpoint was stroke, systemic embolism, or covert stroke detected on the three-year MRI. Safety outcomes included fatal or major bleeding. Enrollment started in 2016, and the trial was stopped in 2022 because of the futility of the primary outcome and an increase in non-major bleeding.

A total of 1,284 patients were randomized (mean age 66 years, 29% women, mean CHA₂DS₂-VASc = 2 with 32% ≥ 3). There were 10 deaths in the rivaroxaban group and seven in the aspirin group. Per protocol, because of repeat AF ablation, 71 patients withdrew. The three-year MRI was accomplished in 1,104 of the 1,134 patients available at that time. The primary composite outcome occurred in five patients (0.8%) in the rivaroxaban group and nine patients (1.4%) in the aspirin group (relative risk [RR], 0.56; 95% confidence interval [CI], 0.19-1.65; P = 0.28). Of the components, stroke occurred in 0.8% vs. 1.1% of patients and new covert stroke by MRI occurred in two patients in the aspirin group. Major bleeding occurred in 1.6% vs. 0.6% of patients in the rivaroxaban group and the aspirin group, respectively (RR, 2.51; 95% CI, 0.79-7.95; P = NS). There were no fatal bleeds or systemic emboli. However, clinically relevant non-major bleeding occurred in 5.5% vs. 1.6% of patients in the rivaroxaban group and the aspirin group, respectively (RR, 3.51; 95% CI, 1.75-7.03).

The authors concluded that among patients more than one year post-successful AF ablation without recurrent AF, there was no significant difference in the rate of stroke or new covert cerebral emboli by MRI in those treated with rivaroxaban compared to low-dose aspirin. Also, there was no significant difference in major or fatal bleeding, but clinically relevant non-major bleeding was more frequent in those taking rivaroxaban.

Commentary

Because successful catheter ablation does not eliminate any risk of AF recurrence, current guidelines recommend indefinite OAC therapy regardless of the success of the procedure. This is a disappointment to many patients with AF because of the bleeding risk of OAC therapy and may deter them from having an ablation. In OCEAN, the components of the primary outcome were rare, and the investigators could not detect any benefit of continuing OAC therapy. A major strength of OCEAN was the use of MRI to detect occult embolic events, which could lead to cognitive decline and death. Although open-label, all events were adjudicated by an independent board. Also, the incidence of major bleeding was low and not significantly different between the two treatment groups. However, there was an increase in clinically relevant minor bleeding with rivaroxaban compared to low-dose aspirin.

There were limitations to OCEAN to consider. Aspirin was the comparator to ablation, not placebo. However, when the data were analyzed assuming aspirin had no effect, the results were similar. Also, it is unlikely that rivaroxaban 20 mg/day would result in different results since there were so few adverse events. Other studies have shown that rivaroxaban 15 mg/day is as effective as 20 mg/day but is associated with less bleeding. The use of Holter monitoring to vet patients for the study would not be expected to be as effective as a loop recorder, so some episodes of asymptomatic recurrent AF could have been missed.

The patients in this study encompassed the spectrum of CHA₂DS₂-VASc scores and, overall, were at moderate risk. A study of only higher-risk patients could have shown different results. In addition, the patients were one or more years post-ablation with no detectable AF and a negative head MRI for occult strokes. Finally, no patients had left atrial appendage occlusion (LAAO) procedures performed. Other studies have shown that LAAO compares favorably to no therapy post-ablation, with stroke rates < 1%. It is unclear which approach is best, since LAAO is not without complications in some patients.

At this time, it seems reasonable to discuss the options of OAC vs. LAAO vs. neither post-ablation in low- to moderate-risk patients.

Michael H. Crawford, MD, is Professor Emeritus of Medicine and Consulting Cardiologist, UCSF Health, San Francisco.