Dangers of Anticoagulation Discontinuation in Atrial Fibrillation After PVI

The risk of stroke is increased in patients with atrial fibrillation (AF) with a CHA₂DS₂-VASc score of 2 or more who discontinue warfarin treatment after pulmonary vein isolation (PVI), according to research published online in JAMA Cardiology.¹

Current guidelines recommend treatment with anticoagulants for 2 to3 months following the procedure, and patients whose CHA₂DS₂-VASc scores indicate elevated stroke risk should continue anticoagulation indefinitely. While some research has found an increased risk after discontinuation of anticoagulants after PVI, findings from observational studies suggest that PVI may lead to a reduction in risk.

For example, one study of post-PVI AF found no difference in the rate of stroke occurrence between those taking anticoagulants and those who had discontinued such treatment.²

In the present retrospective study, researchers from multiple Swedish universities used data from 6 national health registries to explore the risk of stroke and cardiovascular events in patients who continued or discontinued anticoagulation following first-time PVI.

The sample consisted of 1585 AF patients (73% male) who underwent PVI at 10 centers over a 6-year period. In addition to PVI and ischemic stroke history, information was collected regarding comorbidities, electrical cardioversions, and warfarin exposure. Additionally, the authors analyzed factors included in patients’ CHA₂DS₂-VASc scores.

The mean (SD) CHA₂DS₂-VASc score was 1.5 (1.4), and the following trends were observed:

• Of the 1175 patients who were followed for more than 1 year post-PVI, 30.6% of them discontinued warfarin in the first year.
• Patients with a CHA₂DS₂-VASc score of 2 or more who discontinued warfarin had higher rates of stroke than those who continued treatment (5 events in 312 years at risk [1.6% per year] vs 4 events in 1192 years at risk [0.3% per year]) (P =.046).
• Patients with a score of 2 or more showed a higher stroke risk following discontinuation of warfarin (hazard ratio [HR]: 4.6; 95% confidence interval [CI], 1.2-17.2; P =.02), as did those with a history of stroke (HR: 13.7; 95% CI, 2.0-91.9; P =.007).
• A total of 11 patients (0.7%) suffered a stroke during the follow-up period.
• At least 953 patients (60.1%) experienced AF relapse beyond 3 months after PVI and had another PVI and/or electrical cardioversion.

These findings further support to the current recommendation that high-risk AF patients continue anticoagulation after PVI.

Study Limitations

• Retrospective, nonrandomized design and potential for missing data.
• Lack of information regarding AF type (paroxysmal, persistent, long-standing persistent, or permanent). 
• During the time period of data collected (2006 to 2012), both CHADS₂ and CHA₂DS_2-VASc were used for stroke risk stratification, meaning that those patients with a CHADS₂ score of 0 may still have been at risk for stroke according to the CHA₂DS_2-VASc score.

References

1. Själander S, Holmqvist F, Smith JG, et al. Assessment of use vs discontinuation of oral anticoagulation after pulmonary vein isolation in patients with atrial fibrillation. JAMA Cardiol. 2016. doi:10.1001/jamacardio.2016.4179.
2. Karasoy D, Gislason GH, Hansen J, et al. Oral anticoagulation therapy after radiofrequency ablation of atrial fibrillation and the risk of thromboembolism and serious bleeding: long-term follow-up in nationwide cohort of Denmark. Eur Heart J. 2015; 36(5):307-314a.