Oct 2, 2014
It’s well accepted that the window for acute atrial fibrillation cardioversion of atrial fibrillation ends at 48 hours post onset. We did a whole episode on that very point. The 48 hour window is now being challenged by the biggest study to date looking on this topic.
Time to Cardioversion for Acute Atrial Fibrillation and Thromboembolic Complications was published as a letter to JAMA on August 13, 2014. Ryan Radecki sent the first FOAMed shot across the bow with this review. You can stop now and check out Ryan's review; he's far more erudite than I. If you need more info, read on...
Study in a nugget: This was a retrospective study from Finland that looked at around 2500 patients with a primary diagnosis of atrial fibrillation (AF), aged 18 years or older, with successful cardioversion in the emergency department within the first 48 hours of AF onset. The primary outcome, a thromboembolic event, was defined as a clinical stroke or systemic embolism confirmed by computerized tomography or magnetic resonance imaging, surgery, or autopsy. Time to cardioversion was determined as the difference between the beginning of arrhythmic symptoms to the exact time of cardioversion. There were 3 groups: less than 12 hours, 12 hours to less than 24 hours, and 24 hours to less than 48 hours.
Under 12 hours: 0.3%
24 to 48 hours: 1.1%.
It seems like 12 hours is the inflection point when risk went up and a CHADS VASC score of greater than 1 increased risk.
I’m not sure where this leaves us, maybe risk stratification in ED cardioversion? This was observational, retrospective, and did not include post cardioversion anticoagulation as an intervention. There is no definitive answer or management change from this letter. It does raise the question of whether we should anticoagulate cardioverted AF patients with over 12 hours of symptoms, or those with a CHADS VASC over 1. However, there is no evidence that a post cardioversion anticoagulation strategy would decrease thromboembolic event rate. Also, the incidence of post cardioversion thromboembolic events in this letter is far higher than reported in other literature.
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Nuotio, Ilpo, et al. "Time to cardioversion for acute atrial fibrillation and thromboembolic complications." JAMA 312.6 (2014): 647-649.