Review
Atrial flutter and the risk of thromboembolism: A systematic review and meta-analysis

https://doi.org/10.1016/j.amjmed.2004.06.048Get rights and content

Purpose

We conducted a systematic review and meta-analysis of observational studies to assess the risk of thromboembolism associated with atrial flutter.

Methods

MEDLINE, EMBASE, bibliographies, and consultation with clinical experts were used to identify studies that report the risk of thromboembolism associated with attempted cardioversion and longer-term risk in chronic atrial flutter. The review process and data extraction were performed by two reviewers. Study event rates were assessed graphically, and a chi-squared test was used to assess heterogeneity across studies. Meta-regression with weighted logistic regression was used to assess the association between study-level clinical factors and reported thromboembolic event rates.

Results

We found 13 studies that reported the risk of thromboembolism associated with cardioversion of atrial flutter. Short-term event rates ranged from 0% to 7.3%. A chi-squared test for heterogeneity was significant (P < 0.001), so results were not pooled. Instead, a meta-regression analysis was performed, which partly explained the heterogeneity across studies. Studies were more likely to report high event rates when they included patients with a prior history of thromboembolism, and to report lower event rates when at least some patients were anticoagulated or if patients underwent echocardiography before cardioversion. Four studies reported the longer-term risk of thromboembolism, and these suggest a yearly event rate of approximately 3% with sustained atrial flutter.

Conclusion

These findings suggest that atrial flutter is indeed associated with an increased risk of thromboembolism, and that clinical factors account for the low event rates reported in some studies.

Section snippets

Search strategy

We identified relevant articles in any language by searching MEDLINE (1966 to present) and EMBASE (1980 to present). Searches were supplemented by scanning bibliographies and contacting experts. The literature search was initially performed late in 2001, and was updated in February 2004 immediately before submission to identify any new studies that might have appeared.

The EMBASE and MEDLINE search strategy used an approach recommended for systematic reviews of observational studies.9 We derived

Results of literature search

Search of online databases yielded 69 articles from MEDLINE and 76 articles from EMBASE, which when combined represented 113 unique articles. After initial screening of abstracts, it was judged that 39 warranted further full-text review. Twelve additional articles were identified by reviewing bibliographies and contacting experts, yielding a total of 51 articles for full-text review. Among these, 12 were excluded because they only presented echocardiographic findings, and 5 were excluded

Discussion

Our systematic review demonstrates that the reported risk of thromboembolism around the time of cardioversion for atrial flutter varies by study, and that study-level clinical factors contribute to the variability in reported event rates. Collectively, the findings of the 16 studies reviewed in detail suggest that the risk of thromboembolism is not negligible.

Seven of 13 studies on the risk around the time of cardioversion reported an event rate of 0%. We anticipate that it is such findings

Acknowledgment

We thank Dr. Andreas Laupacis (Faculty of Medicine, University of Toronto) for helping us find relevant articles for this systematic review. Dr. Ghali thanks the Department of Medicine and the Institute for Social and Preventive Medicine at the University of Lausanne for hosting him for a sabbatical period during which much of this research was completed.

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    Dr. Ghali is funded by a Health Scholar Award from the Alberta Heritage Foundation for Medical Research, and by a Government of Canada Research Chair in Health Services Research. Dr. Exner is also funded by the Alberta Heritage Foundation for Medical Research.

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