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Afib and Aflutter: Should We Be “Lumpers” or “Splitters”?


Results of a new study may prompt you to rethink how you approach anticoagulation for these 2 arrhythmias. Are they 1 entity, or 2?

Back in the day

I still remember the days when I was a resident at the Brigham and Women’s Hospital in Boston and there was a difference in how we approached anticoagulation between patients who presented with atrial fibrillation (AF) and those with atrial flutter (AFL). The old adage stated that those with AFL had organized atrial activity (as evidence by those “flutter waves” on ECG) whereas those with AF had disorganized atrial activity and therefore warranted anticoagulation if the CHA2DS2-Vasc score was high. Somewhere during my residency, the pendulum swung in the opposite direction and guidelines changed so we anticoagulated all patients with AFL or AF.

Now, a recent Taiwanese study published in JAMA Network Open calls this practice into question, threatening to send the pendulum back in the other direction.

This was a case-control cohort study of 219,416 Taiwanese age- and sex-matched individuals followed over 12 years with the majority of patients having AF (n=188,811, mean age ~74 years) and 6121 having atrial flutter (AFL, [mean age ~68 years]) (matched with 24,484 in the control cohort). The AFL and control cohorts were comprised of a younger population with a lower percentage of women and lower CHA2DS2-Vasc scores compared to the AF cohort. Stratifying by CHA2DS2-Vasc scores, the AF vs AFL patients had a risk of ischemic stroke and heart failure hospitalization beyond a CHA2DS2-Vasc score of 1 or higher. The incidence of ischemic stroke was significantly higher for AFL patients vs controls only at CHA2DS2-Vasc score of 5 to 9. Essentially, the CHA2DS2-Vasc scoring system did not predict risk for ischemic stroke in the same way in patients with AF and AFL. A score of 1 for AF was equivalent (based on outcomes) to a score of 2 for AFL and a score of 2 in AF was equivalent to a score of 4 for AFL patients.

Back to the future?

This study prompts us to rethink our current paradigm of “lumping” AF and AFL patients together rather than “splitting” AF and isolated AFL patients; the results suggest that the outcomes in AFL are different from AF and beyond that, perhaps that there should be different scoring systems to assess risk and determine risk-benefit ratio of oral anticoagulation in the two conditions.

Critics of the study, however, warn not to draw immediate conclusions from these observational findings. Study limitations include residual confounding (despite matching) of the results and that they are limited to a Taiwanese-only patient cohort. Furthermore, it is believed that AFL and AF are diseases on the same spectrum and that they often coexist in a single patient or that AFL can degenerate into AF.

What about you – are you a lumper or a splitter?

Please send your comments to Editor@patientcareonline.com


Lin Y, Chen Y, Chen T, et al. Comparison of clinical outcomes among patients with atrial fibrillation or atrial flutter stratified by CHA2DS2-VASc score. JAMA Network Open. 2018;1(4):e180941. doi:10.1001/jamanetworkopen.2018.0941

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